Kees Cook [Tue, 9 Nov 2021 02:33:37 +0000 (18:33 -0800)]
binfmt_elf: reintroduce using MAP_FIXED_NOREPLACE
Commit e5e9f70945f4 ("elf: don't use MAP_FIXED_NOREPLACE for elf
executable mappings") reverted back to using MAP_FIXED to map ELF LOAD
segments because it was found that the segments in some binaries overlap
and can cause MAP_FIXED_NOREPLACE to fail.
The original intent of MAP_FIXED_NOREPLACE in the ELF loader was to
prevent the silent clobbering of an existing mapping (e.g. stack) by
the ELF image, which could lead to exploitable conditions. Quoting
commit d03c58df02c8 ("fs, elf: drop MAP_FIXED usage from elf_map"),
which originally introduced the use of MAP_FIXED_NOREPLACE in the
loader:
Both load_elf_interp and load_elf_binary rely on elf_map to map
segments [to a specific] address and they use MAP_FIXED to enforce
that. This is however [a] dangerous thing prone to silent data
corruption which can be even exploitable.
...
Let's take CVE-2017-1000253 as an example ... we could end up mapping
[the executable] over the existing stack ... The [stack layout] issue
has been fixed since then ... So we should be safe and any [similar]
attack should be impractical. On the other hand this is just too
subtle [an] assumption ... it can break quite easily and [be] hard to
spot.
...
Address this [weakness] by changing MAP_FIXED to the newly added
MAP_FIXED_NOREPLACE. This will mean that mmap will fail if there is
an existing mapping clashing with the requested one [instead of
silently] clobbering it.
Then processing ET_DYN binaries the loader already calculates a total
size for the image when the first segment is mapped, maps the entire
image, and then unmaps the remainder before the remaining segments are
then individually mapped.
To avoid the earlier problems (legitimate overlapping LOAD segments
specified in the ELF), apply the same logic to ET_EXEC binaries as well.
For both ET_EXEC and ET_DYN+INTERP use MAP_FIXED_NOREPLACE for the
initial total size mapping and then use MAP_FIXED to build the final
(possibly legitimately overlapping) mappings. For ET_DYN w/out INTERP,
continue to map at a system-selected address in the mmap region.
Link: https://lkml.kernel.org/r/20210916215947.3993776-1-keescook@chromium.org Link: https://lore.kernel.org/lkml/1595869887-23307-2-git-send-email-anthony.yznaga@oracle.com Co-developed-by: Anthony Yznaga <anthony.yznaga@oracle.com> Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com> Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Michal Hocko <mhocko@suse.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Chen Jingwen <chenjingwen6@huawei.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andrei Vagin <avagin@openvz.org> Cc: Khalid Aziz <khalid.aziz@oracle.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Thomas Gleixner [Tue, 9 Nov 2021 02:33:25 +0000 (18:33 -0800)]
mm/scatterlist: replace the !preemptible warning in sg_miter_stop()
sg_miter_stop() checks for disabled preemption before unmapping a page
via kunmap_atomic(). The kernel doc mentions under context that
preemption must be disabled if SG_MITER_ATOMIC is set.
There is no active requirement for the caller to have preemption
disabled before invoking sg_mitter_stop(). The sg_mitter_*()
implementation itself has no such requirement.
In fact, preemption is disabled by kmap_atomic() as part of
sg_miter_next() and remains disabled as long as there is an active
SG_MITER_ATOMIC mapping. This is a consequence of kmap_atomic() and not
a requirement for sg_mitter_*() itself.
The user chooses SG_MITER_ATOMIC because it uses the API in a context
where blocking is not possible or blocking is possible but he chooses a
lower weight mapping which is not available on all CPUs and so it might
need less overhead to setup at a price that now preemption will be
disabled.
The kmap_atomic() implementation on PREEMPT_RT does not disable
preemption. It simply disables CPU migration to ensure that the task
remains on the same CPU while the caller remains preemptible. This in
turn triggers the warning in sg_miter_stop() because preemption is
allowed.
The PREEMPT_RT and !PREEMPT_RT implementation of kmap_atomic() disable
pagefaults as a requirement. It is sufficient to check for this instead
of disabled preemption.
Check for disabled pagefault handler in the SG_MITER_ATOMIC case.
Remove the "preemption disabled" part from the kernel doc as the
sg_milter*() implementation does not care.
[bigeasy@linutronix.de: commit description]
Link: https://lkml.kernel.org/r/20211015211409.cqopacv3pxdwn2ty@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Lucas De Marchi [Tue, 9 Nov 2021 02:33:19 +0000 (18:33 -0800)]
include/linux/string_helpers.h: add linux/string.h for strlen()
linux/string_helpers.h uses strlen(), so include the correponding header.
Otherwise we get a compilation error if it's not also included by whoever
included the helper.
Imran Khan [Tue, 9 Nov 2021 02:33:16 +0000 (18:33 -0800)]
lib, stackdepot: add helper to print stack entries into buffer
To print stack entries into a buffer, users of stackdepot, first get a
list of stack entries using stack_depot_fetch and then print this list
into a buffer using stack_trace_snprint. Provide a helper in stackdepot
for this purpose. Also change above mentioned users to use this helper.
[imran.f.khan@oracle.com: fix build error] Link: https://lkml.kernel.org/r/20210915175321.3472770-4-imran.f.khan@oracle.com
[imran.f.khan@oracle.com: export stack_depot_snprint() to modules] Link: https://lkml.kernel.org/r/20210916133535.3592491-4-imran.f.khan@oracle.com Link: https://lkml.kernel.org/r/20210915014806.3206938-4-imran.f.khan@oracle.com Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Suggested-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Jani Nikula <jani.nikula@intel.com> [i915] Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: David Airlie <airlied@linux.ie> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Imran Khan [Tue, 9 Nov 2021 02:33:12 +0000 (18:33 -0800)]
lib, stackdepot: add helper to print stack entries
To print a stack entries, users of stackdepot, first use stack_depot_fetch
to get a list of stack entries and then use stack_trace_print to print
this list. Provide a helper in stackdepot to print stack entries based on
stackdepot handle. Also change above mentioned users to use this helper.
Imran Khan [Tue, 9 Nov 2021 02:33:09 +0000 (18:33 -0800)]
lib, stackdepot: check stackdepot handle before accessing slabs
Patch series "lib, stackdepot: check stackdepot handle before accessing slabs", v2.
PATCH-1: Checks validity of a stackdepot handle before proceeding to
access stackdepot slab/objects.
PATCH-2: Adds a helper in stackdepot, to allow users to print stack
entries just by specifying the stackdepot handle. It also changes such
users to use this new interface.
PATCH-3: Adds a helper in stackdepot, to allow users to print stack
entries into buffers just by specifying the stackdepot handle and
destination buffer. It also changes such users to use this new interface.
This patch (of 3):
stack_depot_save allocates slabs that will be used for storing objects in
future.If this slab allocation fails we may get to a situation where space
allocation for a new stack_record fails, causing stack_depot_save to
return 0 as handle. If user of this handle ends up invoking
stack_depot_fetch with this handle value, current implementation of
stack_depot_fetch will end up using slab from wrong index. To avoid this
check handle value at the beginning.
Lukas Bulwahn [Tue, 9 Nov 2021 02:33:02 +0000 (18:33 -0800)]
MAINTAINERS: rectify entry for INTEL KEEM BAY DRM DRIVER
Commit 6f6a0eb6de48 ("drm/kmb: Build files for KeemBay Display driver")
refers to the non-existing file intel,kmb_display.yaml in
Documentation/devicetree/bindings/display/.
Commit 5c7fc9bda4a6 ("dt-bindings: display: Add support for Intel
KeemBay Display") originating from the same patch series however adds
the file intel,keembay-display.yaml in that directory instead.
So, refer to intel,keembay-display.yaml in the INTEL KEEM BAY DRM DRIVER
section instead.
Link: https://lkml.kernel.org/r/20211026141902.4865-4-lukas.bulwahn@gmail.com Fixes: 6f6a0eb6de48 ("drm/kmb: Build files for KeemBay Display driver") Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Cc: Anitha Chrisanthus <anitha.chrisanthus@intel.com> Cc: Edmund Dea <edmund.j.dea@intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Joe Perches <joe@perches.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Cc: Punit Agrawal <punit1.agrawal@toshiba.co.jp> Cc: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de> Cc: Rob Herring <robh+dt@kernel.org> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Wilken Gottwalt <wilken.gottwalt@posteo.net> Cc: Yu Chen <chenyu56@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Lukas Bulwahn [Tue, 9 Nov 2021 02:32:59 +0000 (18:32 -0800)]
MAINTAINERS: rectify entry for HIKEY960 ONBOARD USB GPIO HUB DRIVER
Commit bd916e14875e ("misc: hisi_hikey_usb: Driver to support onboard
USB gpio hub on Hikey960") refers to the non-existing file
Documentation/devicetree/bindings/misc/hisilicon-hikey-usb.yaml, but
this commit's patch series does not add any related devicetree binding
in misc.
So, just drop this file reference in HIKEY960 ONBOARD USB GPIO HUB DRIVER.
Link: https://lkml.kernel.org/r/20211026141902.4865-3-lukas.bulwahn@gmail.com Fixes: bd916e14875e ("misc: hisi_hikey_usb: Driver to support onboard USB gpio hub on Hikey960") Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Cc: Anitha Chrisanthus <anitha.chrisanthus@intel.com> Cc: Edmund Dea <edmund.j.dea@intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Joe Perches <joe@perches.com> Cc: John Stultz <john.stultz@linaro.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Cc: Punit Agrawal <punit1.agrawal@toshiba.co.jp> Cc: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de> Cc: Rob Herring <robh+dt@kernel.org> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Wilken Gottwalt <wilken.gottwalt@posteo.net> Cc: Yu Chen <chenyu56@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Lukas Bulwahn [Tue, 9 Nov 2021 02:32:55 +0000 (18:32 -0800)]
MAINTAINERS: rectify entry for ARM/TOSHIBA VISCONTI ARCHITECTURE
Patch series "Rectify file references for dt-bindings in MAINTAINERS", v5.
A patch series that cleans up some file references for dt-bindings in
MAINTAINERS.
This patch (of 4):
Commit dc064c9c25ac ("MAINTAINERS: Add information for Toshiba Visconti
ARM SoCs") refers to the non-existing file toshiba,tmpv7700-pinctrl.yaml
in ./Documentation/devicetree/bindings/pinctrl/. Commit e81d1bfad0df
("pinctrl: Add DT bindings for Toshiba Visconti TMPV7700 SoC")
originating from the same patch series however adds the file
toshiba,visconti-pinctrl.yaml in that directory instead.
So, refer to toshiba,visconti-pinctrl.yaml in the ARM/TOSHIBA VISCONTI
ARCHITECTURE section instead.
Link: https://lkml.kernel.org/r/20211026141902.4865-1-lukas.bulwahn@gmail.com Link: https://lkml.kernel.org/r/20211026141902.4865-2-lukas.bulwahn@gmail.com Fixes: dc064c9c25ac ("MAINTAINERS: Add information for Toshiba Visconti ARM SoCs") Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com> Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Reviewed-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Cc: Rob Herring <robh+dt@kernel.org> Cc: Punit Agrawal <punit1.agrawal@toshiba.co.jp> Cc: Anitha Chrisanthus <anitha.chrisanthus@intel.com> Cc: Wilken Gottwalt <wilken.gottwalt@posteo.net> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Yu Chen <chenyu56@huawei.com> Cc: Sam Ravnborg <sam@ravnborg.org> Cc: Edmund Dea <edmund.j.dea@intel.com> Cc: Joe Perches <joe@perches.com> Cc: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
_Static_assert() is evaluated already in the compiler's frontend, and
gives a somehat more to-the-point error, compared to the BUILD_BUG_ON
macro, which only fires after the optimizer has had a chance to
eliminate calls to functions marked with __attribute__((error)). In
theory, this might make builds a tiny bit faster.
There's also a little less gunk in the error message emitted:
lib/sort.c: In function `foo':
include/linux/build_bug.h:78:41: error: static assertion failed: "pointer type mismatch in container_of()"
78 | #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
compared to
lib/sort.c: In function `foo':
include/linux/compiler_types.h:322:38: error: call to `__compiletime_assert_2' declared with attribute error: pointer type mismatch in container_of()
322 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
While at it, fix the copy-pasto in container_of_safe().
bottom_half.h needs _THIS_IP_ to be standalone, so split that and
_RET_IP_ out from kernel.h into the new instruction_pointer.h. kernel.h
directly needs them, so include it there and replace the include of
kernel.h with this new file in bottom_half.h.
Link: https://lkml.kernel.org/r/20211028161248.45232-1-andriy.shevchenko@linux.intel.com Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy Shevchenko [Tue, 9 Nov 2021 02:32:12 +0000 (18:32 -0800)]
kernel.h: split out container_of() and typeof_member() macros
kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt cleaning it up by splitting out container_of() and
typeof_member() macros.
For time being include new header back to kernel.h to avoid twisted
indirected includes for existing users.
Note, there are _a lot_ of headers and modules that include kernel.h
solely for one of these macros and this allows to unburden compiler for
the twisted inclusion paths and to make new code cleaner in the future.
Link: https://lkml.kernel.org/r/20211013170417.87909-3-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Brendan Higgins <brendanhiggins@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Cameron <jic23@kernel.org> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sakari Ailus <sakari.ailus@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Thorsten Leemhuis <regressions@leemhuis.info> Cc: Waiman Long <longman@redhat.com> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andy Shevchenko [Tue, 9 Nov 2021 02:32:08 +0000 (18:32 -0800)]
kernel.h: drop unneeded <linux/kernel.h> inclusion from other headers
Patch series "kernel.h further split", v5.
kernel.h is a set of something which is not related to each other and
often used in non-crossed compilation units, especially when drivers
need only one or two macro definitions from it.
This patch (of 7):
There is no evidence we need kernel.h inclusion in certain headers.
Drop unneeded <linux/kernel.h> inclusion from other headers.
[sfr@canb.auug.org.au: bottom_half.h needs kernel] Link: https://lkml.kernel.org/r/20211015202908.1c417ae2@canb.auug.org.au Link: https://lkml.kernel.org/r/20211013170417.87909-1-andriy.shevchenko@linux.intel.com Link: https://lkml.kernel.org/r/20211013170417.87909-2-andriy.shevchenko@linux.intel.com Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Brendan Higgins <brendanhiggins@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Will Deacon <will@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Sakari Ailus <sakari.ailus@linux.intel.com> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Cc: Jonathan Cameron <jic23@kernel.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Thorsten Leemhuis <regressions@leemhuis.info> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stephen Brennan [Tue, 9 Nov 2021 02:32:05 +0000 (18:32 -0800)]
proc: allow pid_revalidate() during LOOKUP_RCU
Problem Description:
When running running ~128 parallel instances of
TZ=/etc/localtime ps -fe >/dev/null
on a 128CPU machine, the %sys utilization reaches 97%, and perf shows
the following code path as being responsible for heavy contention on the
d_lockref spinlock:
The reason is that pid_revalidate() is triggering a drop from RCU to ref
path walk mode. All concurrent path lookups thus try to grab a
reference to the dentry for /proc/, before re-executing pid_revalidate()
and then stepping into the /proc/$pid directory. Thus there is huge
spinlock contention.
This patch allows pid_revalidate() to execute in RCU mode, meaning that
the path lookup can successfully enter the /proc/$pid directory while
still in RCU mode. Later on, the path lookup may still drop into ref
mode, but the contention will be much reduced at this point.
By applying this patch, %sys utilization falls to around 85% under the
same workload, and the number of ps processes executed per unit time
increases by 3x-4x. Although this particular workload is a bit
contrived, we have seen some large collections of eager monitoring
scripts which produced similarly high %sys time due to contention in the
/proc directory.
As a result this patch, Al noted that several procfs methods which were
only called in ref-walk mode could now be called from RCU mode. To
ensure that this patch is safe, I audited all the inode get_link and
permission() implementations, as well as dentry d_revalidate()
implementations, in fs/proc. The purpose here is to ensure that they
either are safe to call in RCU (i.e. don't sleep) or correctly bail out
of RCU mode if they don't support it. My analysis shows that all
at-risk procfs methods are safe to call under RCU, and thus this patch
is safe.
Procfs RCU-walk Analysis:
This analysis is up-to-date with 5.15-rc3. When called under RCU mode,
these functions have arguments as follows:
* get_link() receives a NULL dentry pointer when called in RCU mode.
* permission() receives MAY_NOT_BLOCK in the mode parameter when called
from RCU.
* d_revalidate() receives LOOKUP_RCU in flags.
For the following functions, either they are trivially RCU safe, or they
explicitly bail at the beginning of the function when they run:
proc_ns_get_link (bails out)
proc_get_link (RCU safe)
proc_pid_get_link (bails out)
map_files_d_revalidate (bails out)
map_misc_d_revalidate (bails out)
proc_net_d_revalidate (RCU safe)
proc_sys_revalidate (bails out, also not under /proc/$pid)
tid_fd_revalidate (bails out)
proc_sys_permission (not under /proc/$pid)
The remainder of the functions require a bit more detail:
* proc_fd_permission: RCU safe. All of the body of this function is
under rcu_read_lock(), except generic_permission() which declares
itself RCU safe in its documentation string.
* proc_self_get_link uses GFP_ATOMIC in the RCU case, so it is RCU aware
and otherwise looks safe. The same is true of proc_thread_self_get_link.
* proc_map_files_get_link: calls ns_capable, which calls capable(), and
thus calls into the audit code (see note #1 below). The remainder is
just a call to the trivially safe proc_pid_get_link().
* proc_pid_permission: calls ptrace_may_access(), which appears RCU
safe, although it does call into the "security_ptrace_access_check()"
hook, which looks safe under smack and selinux. Just the audit code is
of concern. Also uses get_task_struct() and put_task_struct(), see
note #2 below.
* proc_tid_comm_permission: Appears safe, though calls put_task_struct
(see note #2 below).
Note #1:
Most of the concern of RCU safety has centered around the audit code.
However, since 6efd7f7e2ba2 ("selinux: slow_avc_audit has become
non-blocking"), it's safe to call this code under RCU. So all of the
above are safe by my estimation.
Note #2: get_task_struct() and put_task_struct():
The majority of get_task_struct() is under RCU read lock, and in any
case it is a simple increment. But put_task_struct() is complex, given
that it could at some point free the task struct, and this process has
many steps which I couldn't manually verify. However, several other
places call put_task_struct() under RCU, so it appears safe to use
here too (see kernel/hung_task.c:165 or rcu/tree-stall.h:296)
Patch description:
pid_revalidate() drops from RCU into REF lookup mode. When many threads
are resolving paths within /proc in parallel, this can result in heavy
spinlock contention on d_lockref as each thread tries to grab a
reference to the /proc dentry (and drop it shortly thereafter).
Investigation indicates that it is not necessary to drop RCU in
pid_revalidate(), as no RCU data is modified and the function never
sleeps. So, remove the LOOKUP_RCU check.
Link: https://lkml.kernel.org/r/20211004175629.292270-2-stephen.s.brennan@oracle.com Signed-off-by: Stephen Brennan <stephen.s.brennan@oracle.com> Cc: Konrad Wilk <konrad.wilk@oracle.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Matthew Wilcox <willy@infradead.org> Cc: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
virtio-mem: kdump mode to sanitize /proc/vmcore access
Although virtio-mem currently supports reading unplugged memory in the
hypervisor, this will change in the future, indicated to the device via
a new feature flag.
We similarly sanitized /proc/kcore access recently. [1]
Let's register a vmcore callback, to allow vmcore code to check if a PFN
belonging to a virtio-mem device is either currently plugged and should
be dumped or is currently unplugged and should not be accessed, instead
mapping the shared zeropage or returning zeroes when reading.
This is important when not capturing /proc/vmcore via tools like
"makedumpfile" that can identify logically unplugged virtio-mem memory
via PG_offline in the memmap, but simply by e.g., copying the file.
Distributions that support virtio-mem+kdump have to make sure that the
virtio_mem module will be part of the kdump kernel or the kdump initrd;
dracut was recently [2] extended to include virtio-mem in the generated
initrd. As long as no special kdump kernels are used, this will
automatically make sure that virtio-mem will be around in the kdump
initrd and sanitize /proc/vmcore access -- with dracut.
With this series, we'll send one virtio-mem state request for every ~2
MiB chunk of virtio-mem memory indicated in the vmcore that we intend to
read/map.
In the future, we might want to allow building virtio-mem for kdump mode
only, even without CONFIG_MEMORY_HOTPLUG and friends: this way, we could
support special stripped-down kdump kernels that have many other config
options disabled; we'll tackle that once required. Further, we might
want to try sensing bigger blocks (e.g., memory sections) first before
falling back to device blocks on demand.
Tested with Fedora rawhide, which contains a recent kexec-tools version
(considering "System RAM (virtio_mem)" when creating the vmcore header)
and a recent dracut version (including the virtio_mem module in the
kdump initrd).
Link: https://lkml.kernel.org/r/20210526093041.8800-1-david@redhat.com Link: https://github.com/dracutdevs/dracut/pull/1157 Link: https://lkml.kernel.org/r/20211005121430.30136-10-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Dave Young <dyoung@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
proc/vmcore: convert oldmem_pfn_is_ram callback to more generic vmcore callbacks
Let's support multiple registered callbacks, making sure that
registering vmcore callbacks cannot fail. Make the callback return a
bool instead of an int, handling how to deal with errors internally.
Drop unused HAVE_OLDMEM_PFN_IS_RAM.
We soon want to make use of this infrastructure from other drivers:
virtio-mem, registering one callback for each virtio-mem device, to
prevent reading unplugged virtio-mem memory.
Handle it via a generic vmcore_cb structure, prepared for future
extensions: for example, once we support virtio-mem on s390x where the
vmcore is completely constructed in the second kernel, we want to detect
and add plugged virtio-mem memory ranges to the vmcore in order for them
to get dumped properly.
Handle corner cases that are unexpected and shouldn't happen in sane
setups: registering a callback after the vmcore has already been opened
(warn only) and unregistering a callback after the vmcore has already been
opened (warn and essentially read only zeroes from that point on).
Link: https://lkml.kernel.org/r/20211005121430.30136-6-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Dave Young <dyoung@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The callback should deal with errors internally, it doesn't make sense
to expose these via pfn_is_ram(). We'll rework the callbacks next.
Right now we consider errors as if "it's RAM"; no functional change.
Link: https://lkml.kernel.org/r/20211005121430.30136-5-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Dave Young <dyoung@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
x86/xen: print a warning when HVMOP_get_mem_type fails
HVMOP_get_mem_type is not expected to fail, "This call failing is
indication of something going quite wrong and it would be good to know
about this." [1]
Let's add a pr_warn_once().
Link: https://lkml.kernel.org/r/3b935aa0-6d85-0bcd-100e-15098add3c4c@oracle.com Link: https://lkml.kernel.org/r/20211005121430.30136-4-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Suggested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Baoquan He <bhe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Young <dyoung@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After removing /dev/kmem, sanitizing /proc/kcore and handling /dev/mem,
this series tackles the last sane way how a VM could accidentially
access logically unplugged memory managed by a virtio-mem device:
/proc/vmcore
When dumping memory via "makedumpfile", PG_offline pages, used by
virtio-mem to flag logically unplugged memory, are already properly
excluded; however, especially when accessing/copying /proc/vmcore "the
usual way", we can still end up reading logically unplugged memory part
of a virtio-mem device.
Patch #1-#3 are cleanups. Patch #4 extends the existing
oldmem_pfn_is_ram mechanism. Patch #5-#7 are virtio-mem refactorings
for patch #8, which implements the virtio-mem logic to query the state
of device blocks.
Patch #8:
"Although virtio-mem currently supports reading unplugged memory in the
hypervisor, this will change in the future, indicated to the device
via a new feature flag. We similarly sanitized /proc/kcore access
recently.
[...]
Distributions that support virtio-mem+kdump have to make sure that the
virtio_mem module will be part of the kdump kernel or the kdump
initrd; dracut was recently [2] extended to include virtio-mem in the
generated initrd. As long as no special kdump kernels are used, this
will automatically make sure that virtio-mem will be around in the
kdump initrd and sanitize /proc/vmcore access -- with dracut"
This is the last remaining bit to support
VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE [3] in the Linux implementation of
virtio-mem.
Note: this is best-effort. We'll never be able to control what runs
inside the second kernel, really, but we also don't have to care: we
only care about sane setups where we don't want our VM getting zapped
once we touch the wrong memory location while dumping. While we usually
expect sane setups to use "makedumfile", nothing really speaks against
just copying /proc/vmcore, especially in environments where HWpoisioning
isn't typically expected. Also, we really don't want to put all our
trust completely on the memmap, so sanitizing also makes sense when just
using "makedumpfile".
zhangyiru [Tue, 9 Nov 2021 02:31:27 +0000 (18:31 -0800)]
mm,hugetlb: remove mlock ulimit for SHM_HUGETLB
Commit 227b81e918be ("mm, hugetlb: add thread name and pid to
SHM_HUGETLB mlock rlimit warning") marked this as deprecated in 2012,
but it is not deleted yet.
Mike says he still sees that message in log files on occasion, so maybe we
should preserve this warning.
Also remove hugetlbfs related user_shm_unlock in ipc/shm.c and remove the
user_shm_unlock after out.
Link: https://lkml.kernel.org/r/20211103105857.25041-1-zhangyiru3@huawei.com Signed-off-by: zhangyiru <zhangyiru3@huawei.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Hugh Dickins <hughd@google.com> Cc: Liu Zixian <liuzixian4@huawei.com> Cc: Michal Hocko <mhocko@suse.com> Cc: wuxu.wu <wuxu.wu@huawei.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Johannes Weiner [Tue, 9 Nov 2021 02:31:24 +0000 (18:31 -0800)]
vfs: keep inodes with page cache off the inode shrinker LRU
Historically (pre-2.5), the inode shrinker used to reclaim only empty
inodes and skip over those that still contained page cache. This caused
problems on highmem hosts: struct inode could put fill lowmem zones
before the cache was getting reclaimed in the highmem zones.
To address this, the inode shrinker started to strip page cache to
facilitate reclaiming lowmem. However, this comes with its own set of
problems: the shrinkers may drop actively used page cache just because
the inodes are not currently open or dirty - think working with a large
git tree. It further doesn't respect cgroup memory protection settings
and can cause priority inversions between containers.
Nowadays, the page cache also holds non-resident info for evicted cache
pages in order to detect refaults. We've come to rely heavily on this
data inside reclaim for protecting the cache workingset and driving swap
behavior. We also use it to quantify and report workload health through
psi. The latter in turn is used for fleet health monitoring, as well as
driving automated memory sizing of workloads and containers, proactive
reclaim and memory offloading schemes.
The consequences of dropping page cache prematurely is that we're seeing
subtle and not-so-subtle failures in all of the above-mentioned
scenarios, with the workload generally entering unexpected thrashing
states while losing the ability to reliably detect it.
To fix this on non-highmem systems at least, going back to rotating
inodes on the LRU isn't feasible. We've tried (commit d660b535dd1c
("mm: don't reclaim inodes with many attached pages")) and failed
(commit 8db492ffc705 ("Revert "mm: don't reclaim inodes with many
attached pages"")).
The issue is mostly that shrinker pools attract pressure based on their
size, and when objects get skipped the shrinkers remember this as
deferred reclaim work. This accumulates excessive pressure on the
remaining inodes, and we can quickly eat into heavily used ones, or
dirty ones that require IO to reclaim, when there potentially is plenty
of cold, clean cache around still.
Instead, this patch keeps populated inodes off the inode LRU in the
first place - just like an open file or dirty state would. An otherwise
clean and unused inode then gets queued when the last cache entry
disappears. This solves the problem without reintroducing the reclaim
issues, and generally is a bit more scalable than having to wade through
potentially hundreds of thousands of busy inodes.
Locking is a bit tricky because the locks protecting the inode state
(i_lock) and the inode LRU (lru_list.lock) don't nest inside the
irq-safe page cache lock (i_pages.xa_lock). Page cache deletions are
serialized through i_lock, taken before the i_pages lock, to make sure
depopulated inodes are queued reliably. Additions may race with
deletions, but we'll check again in the shrinker. If additions race
with the shrinker itself, we're protected by the i_lock: if find_inode()
or iput() win, the shrinker will bail on the elevated i_count or
I_REFERENCED; if the shrinker wins and goes ahead with the inode, it
will set I_FREEING and inhibit further igets(), which will cause the
other side to create a new instance of the inode instead.
Link: https://lkml.kernel.org/r/20210614211904.14420-4-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Roman Gushchin <guro@fb.com> Cc: Tejun Heo <tj@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Colin Ian King [Fri, 5 Nov 2021 20:48:24 +0000 (13:48 -0700)]
mm/damon: fix a few spelling mistakes in comments and a pr_debug message
There are a few spelling mistakes in the code. Fix these.
Link: https://lkml.kernel.org/r/20211028184157.614544-1-colin.i.king@gmail.com Signed-off-by: Colin Ian King <colin.i.king@gmail.com> Reviewed-by: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Changbin Du [Fri, 5 Nov 2021 20:48:22 +0000 (13:48 -0700)]
mm/damon: simplify stop mechanism
A kernel thread can exit gracefully with kthread_stop(). So we don't
need a new flag 'kdamond_stop'. And to make sure the task struct is not
freed when accessing it, get reference to it before termination.
Link: https://lkml.kernel.org/r/20211027130517.4404-1-changbin.du@gmail.com Signed-off-by: Changbin Du <changbin.du@gmail.com> Reviewed-by: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some descriptions of page flags in 'pagemap.rst' are written in
assumption of none-rst, which respects every new line, as below:
7 - SLAB
page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator
When compound page is used, SLUB/SLQB will only set this flag on the head
Because rst ignores the new line between the first sentence and second
sentence, resulting html looks a little bit weird, as below.
7 - SLAB
page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator When
^
compound page is used, SLUB/SLQB will only set this flag on the head
page; SLOB will not flag it at all.
This change makes it more natural and consistent with other parts in the
rendered version.
Link: https://lkml.kernel.org/r/20211022090311.3856-5-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:48:16 +0000 (13:48 -0700)]
Docs/admin-guide/mm/damon/start: simplify the content
Information in 'TL; DR' section of 'Getting Started' is duplicated in
other parts of the doc. It is also asking readers to visit the access
pattern visualizations gallery web site to show the results of example
visualization commands, while the users of the commands can use terminal
output.
To make the doc simple, this removes the duplicated 'TL; DR' section and
replaces the visualization example commands with versions using terminal
outputs.
Link: https://lkml.kernel.org/r/20211022090311.3856-4-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:48:13 +0000 (13:48 -0700)]
Docs/admin-guide/mm/damon/start: fix a wrong link
The 'Getting Started' of DAMON is providing a link to DAMON's user
interface document while saying about its user space tool's detailed
usages. This fixes the link.
Link: https://lkml.kernel.org/r/20211022090311.3856-3-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This implements a new kernel subsystem that finds cold memory regions
using DAMON and reclaims those immediately. It is intended to be used
as proactive lightweigh reclamation logic for light memory pressure.
For heavy memory pressure, it could be inactivated and fall back to the
traditional page-scanning based reclamation.
It's implemented on top of DAMON framework to use the DAMON-based
Operation Schemes (DAMOS) feature. It utilizes all the DAMOS features
including speed limit, prioritization, and watermarks.
It could be enabled and tuned in boot time via the kernel boot
parameter, and in run time via its module parameters
('/sys/module/damon_reclaim/parameters/') interface.
[yangyingliang@huawei.com: fix error return code in damon_reclaim_turn()] Link: https://lkml.kernel.org/r/20211025124500.2758060-1-yangyingliang@huawei.com Link: https://lkml.kernel.org/r/20211019150731.16699-15-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:47 +0000 (13:47 -0700)]
mm/damon/schemes: activate schemes based on a watermarks mechanism
DAMON-based operation schemes need to be manually turned on and off. In
some use cases, however, the condition for turning a scheme on and off
would depend on the system's situation. For example, schemes for
proactive pages reclamation would need to be turned on when some memory
pressure is detected, and turned off when the system has enough free
memory.
For easier control of schemes activation based on the system situation,
this introduces a watermarks-based mechanism. The client can describe
the watermark metric (e.g., amount of free memory in the system),
watermark check interval, and three watermarks, namely high, mid, and
low. If the scheme is deactivated, it only gets the metric and compare
that to the three watermarks for every check interval. If the metric is
higher than the high watermark, the scheme is deactivated. If the
metric is between the mid watermark and the low watermark, the scheme is
activated. If the metric is lower than the low watermark, the scheme is
deactivated again. This is to allow users fall back to traditional
page-granularity mechanisms.
Link: https://lkml.kernel.org/r/20211019150731.16699-12-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:37 +0000 (13:47 -0700)]
mm/damon/vaddr,paddr: support pageout prioritization
This makes the default monitoring primitives for virtual address spaces
and the physical address sapce to support memory regions prioritization
for 'PAGEOUT' DAMOS action. It calculates hotness of each region as
weighted sum of 'nr_accesses' and 'age' of the region and get the
priority score as reverse of the hotness, so that cold regions can be
paged out first.
Link: https://lkml.kernel.org/r/20211019150731.16699-9-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:33 +0000 (13:47 -0700)]
mm/damon/schemes: prioritize regions within the quotas
This makes DAMON apply schemes to regions having higher priority first,
if it cannot apply schemes to all regions due to the quotas.
The prioritization function should be implemented in the monitoring
primitives. Those would commonly calculate the priority of the region
using attributes of regions, namely 'size', 'nr_accesses', and 'age'.
For example, some primitive would calculate the priority of each region
using a weighted sum of 'nr_accesses' and 'age' of the region.
The optimal weights would depend on give environments, so this makes
those customizable. Nevertheless, the score calculation functions are
only encouraged to respect the weights, not mandated.
Link: https://lkml.kernel.org/r/20211019150731.16699-8-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:23 +0000 (13:47 -0700)]
mm/damon/schemes: implement time quota
The size quota feature of DAMOS is useful for IO resource-critical
systems, but not so intuitive for CPU time-critical systems. Systems
using zram or zswap-like swap device would be examples.
To provide another intuitive ways for such systems, this implements
time-based quota for DAMON-based Operation Schemes. If the quota is
set, DAMOS tries to use only up to the user-defined quota of CPU time
within a given time window.
Link: https://lkml.kernel.org/r/20211019150731.16699-5-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:20 +0000 (13:47 -0700)]
mm/damon/schemes: skip already charged targets and regions
If DAMOS has stopped applying action in the middle of a group of memory
regions due to its size quota, it starts the work again from the
beginning of the address space in the next charge window. If there is a
huge memory region at the beginning of the address space and it fulfills
the scheme's target data access pattern always, the action will applied
to only the region.
This mitigates the case by skipping memory regions that charged in
current charge window at the beginning of next charge window.
Link: https://lkml.kernel.org/r/20211019150731.16699-4-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:16 +0000 (13:47 -0700)]
mm/damon/schemes: implement size quota for schemes application speed control
There could be arbitrarily large memory regions fulfilling the target
data access pattern of a DAMON-based operation scheme. In the case,
applying the action of the scheme could incur too high overhead. To
provide an intuitive way for avoiding it, this implements a feature
called size quota. If the quota is set, DAMON tries to apply the action
only up to the given amount of memory regions within a given time
window.
Link: https://lkml.kernel.org/r/20211019150731.16699-3-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:47:13 +0000 (13:47 -0700)]
mm/damon/paddr: support the pageout scheme
Introduction
============
This patchset 1) makes the engine for general data access
pattern-oriented memory management (DAMOS) be more useful for production
environments, and 2) implements a static kernel module for lightweight
proactive reclamation using the engine.
Proactive Reclamation
---------------------
On general memory over-committed systems, proactively reclaiming cold
pages helps saving memory and reducing latency spikes that incurred by
the direct reclaim or the CPU consumption of kswapd, while incurring
only minimal performance degradation[2].
A Free Pages Reporting[8] based memory over-commit virtualization system
would be one more specific use case. In the system, the guest VMs
reports their free memory to host, and the host reallocates the reported
memory to other guests. As a result, the system's memory utilization
can be maximized. However, the guests could be not so memory-frugal,
because some kernel subsystems and user-space applications are designed
to use as much memory as available. Then, guests would report only
small amount of free memory to host, results in poor memory utilization.
Running the proactive reclamation in such guests could help mitigating
this problem.
Google has also implemented this idea and using it in their data center.
They further proposed upstreaming it in LSFMM'19, and "the general
consensus was that, while this sort of proactive reclaim would be useful
for a number of users, the cost of this particular solution was too high
to consider merging it upstream"[3]. The cost mainly comes from the
coldness tracking. Roughly speaking, the implementation periodically
scans the 'Accessed' bit of each page. For the reason, the overhead
linearly increases as the size of the memory and the scanning frequency
grows. As a result, Google is known to dedicating one CPU for the work.
That's a reasonable option to someone like Google, but it wouldn't be so
to some others.
DAMON and DAMOS: An engine for data access pattern-oriented memory management
-----------------------------------------------------------------------------
DAMON[4] is a framework for general data access monitoring. Its
adaptive monitoring overhead control feature minimizes its monitoring
overhead. It also let the upper-bound of the overhead be configurable
by clients, regardless of the size of the monitoring target memory.
While monitoring 70 GiB memory of a production system every 5
milliseconds, it consumes less than 1% single CPU time. For this, it
could sacrify some of the quality of the monitoring results.
Nevertheless, the lower-bound of the quality is configurable, and it
uses a best-effort algorithm for better quality. Our test results[5]
show the quality is practical enough. From the production system
monitoring, we were able to find a 4 KiB region in the 70 GiB memory
that shows highest access frequency.
We normally don't monitor the data access pattern just for fun but to
improve something like memory management. Proactive reclamation is one
such usage. For such general cases, DAMON provides a feature called
DAMon-based Operation Schemes (DAMOS)[6]. It makes DAMON an engine for
general data access pattern oriented memory management. Using this,
clients can ask DAMON to find memory regions of specific data access
pattern and apply some memory management action (e.g., page out, move to
head of the LRU list, use huge page, ...). We call the request
'scheme'.
Proactive Reclamation on top of DAMON/DAMOS
-------------------------------------------
Therefore, by using DAMON for the cold pages detection, the proactive
reclamation's monitoring overhead issue can be solved. Actually, we
previously implemented a version of proactive reclamation using DAMOS
and achieved noticeable improvements with our evaluation setup[5].
Nevertheless, it more for a proof-of-concept, rather than production
uses. It supports only virtual address spaces of processes, and require
additional tuning efforts for given workloads and the hardware. For the
tuning, we introduced a simple auto-tuning user space tool[8]. Google
is also known to using a ML-based similar approach for their fleets[2].
But, making it just works with intuitive knobs in the kernel would be
helpful for general users.
To this end, this patchset improves DAMOS to be ready for such
production usages, and implements another version of the proactive
reclamation, namely DAMON_RECLAIM, on top of it.
DAMOS Improvements: Aggressiveness Control, Prioritization, and Watermarks
--------------------------------------------------------------------------
First of all, the current version of DAMOS supports only virtual address
spaces. This patchset makes it supports the physical address space for
the page out action.
Next major problem of the current version of DAMOS is the lack of the
aggressiveness control, which can results in arbitrary overhead. For
example, if huge memory regions having the data access pattern of
interest are found, applying the requested action to all of the regions
could incur significant overhead. It can be controlled by tuning the
target data access pattern with manual or automated approaches[2,7].
But, some people would prefer the kernel to just work with only
intuitive tuning or default values.
For such cases, this patchset implements a safeguard, namely time/size
quota. Using this, the clients can specify up to how much time can be
used for applying the action, and/or up to how much memory regions the
action can be applied within a user-specified time duration. A followup
question is, to which memory regions should the action applied within
the limits? We implement a simple regions prioritization mechanism for
each action and make DAMOS to apply the action to high priority regions
first. It also allows clients tune the prioritization mechanism to use
different weights for size, access frequency, and age of memory regions.
This means we could use not only LRU but also LFU or some fancy
algorithms like CAR[9] with lightweight overhead.
Though DAMON is lightweight, someone would want to remove even the cold
pages monitoring overhead when it is unnecessary. Currently, it should
manually turned on and off by clients, but some clients would simply
want to turn it on and off based on some metrics like free memory ratio
or memory fragmentation. For such cases, this patchset implements a
watermarks-based automatic activation feature. It allows the clients
configure the metric of their interest, and three watermarks of the
metric. If the metric is higher than the high watermark or lower than
the low watermark, the scheme is deactivated. If the metric is lower
than the mid watermark but higher than the low watermark, the scheme is
activated.
DAMON-based Reclaim
-------------------
Using the improved version of DAMOS, this patchset implements a static
kernel module called 'damon_reclaim'. It finds memory regions that
didn't accessed for specific time duration and page out. Consuming too
much CPU for the paging out operations, or doing pageout too frequently
can be critical for systems configuring their swap devices with
software-defined in-memory block devices like zram/zswap or total number
of writes limited devices like SSDs, respectively. To avoid the
problems, the time/size quotas can be configured. Under the quotas, it
pages out memory regions that didn't accessed longer first. Also, to
remove the monitoring overhead under peaceful situation, and to fall
back to the LRU-list based page granularity reclamation when it doesn't
make progress, the three watermarks based activation mechanism is used,
with the free memory ratio as the watermark metric.
For convenient configurations, it provides several module parameters.
Using these, sysadmins can enable/disable it, and tune its parameters
including the coldness identification time threshold, the time/size
quotas and the three watermarks.
Evaluation
==========
In short, DAMON_RECLAIM with 50ms/s time quota and regions
prioritization on v5.15-rc5 Linux kernel with ZRAM swap device achieves
38.58% memory saving with only 1.94% runtime overhead. For this,
DAMON_RECLAIM consumes only 4.97% of single CPU time.
Setup
-----
We evaluate DAMON_RECLAIM to show how each of the DAMOS improvements
make effect. For this, we measure DAMON_RECLAIM's CPU consumption,
entire system memory footprint, total number of major page faults, and
runtime of 24 realistic workloads in PARSEC3 and SPLASH-2X benchmark
suites on my QEMU/KVM based virtual machine. The virtual machine runs
on an i3.metal AWS instance, has 130GiB memory, and runs a linux kernel
built on latest -mm tree[1] plus this patchset. It also utilizes a 4
GiB ZRAM swap device. We repeats the measurement 5 times and use
averages.
With coldness identification threshold of 5 seconds, DAMON_RECLAIM
without the time quota-based speed limit achieves 47.21% memory saving,
but incur 4.59% runtime slowdown to the workloads on average. For this,
DAMON_RECLAIM consumes about 11.28% single CPU time.
Applying time quotas of 200ms/s, 50ms/s, and 10ms/s without the regions
prioritization reduces the slowdown to 4.89%, 2.65%, and 1.5%,
respectively. Time quota of 200ms/s (20%) makes no real change compared
to the quota unapplied version, because the quota unapplied version
consumes only 11.28% CPU time. DAMON_RECLAIM's CPU utilization also
similarly reduced: 11.24%, 5.51%, and 2.01% of single CPU time. That
is, the overhead is proportional to the speed limit. Nevertheless, it
also reduces the memory saving because it becomes less aggressive. In
detail, the three variants show 48.76%, 37.83%, and 7.85% memory saving,
respectively.
Applying the regions prioritization (page out regions that not accessed
longer first within the time quota) further reduces the performance
degradation. Runtime slowdowns and total number of major page faults
increase has been 4.89%/218,690% -> 4.39%/166,136% (200ms/s),
2.65%/111,886% -> 1.94%/59,053% (50ms/s), and 1.5%/34,973.40% ->
2.08%/8,781.75% (10ms/s). The runtime under 10ms/s time quota has
increased with prioritization, but apparently that's under the margin of
error.
time quota prioritization memory_saving cpu_util slowdown pgmajfaults overhead
N N 47.21% 11.28% 4.59% 194,802%
200ms/s N 48.76% 11.24% 4.89% 218,690%
50ms/s N 37.83% 5.51% 2.65% 111,886%
10ms/s N 7.85% 2.01% 1.5% 34,793.40%
200ms/s Y 50.08% 10.38% 4.39% 166,136%
50ms/s Y 38.58% 4.97% 1.94% 59,053%
10ms/s Y 3.63% 1.73% 2.08% 8,781.75%
Baseline and Complete Git Trees
===============================
The patches are based on the latest -mm tree
(v5.15-rc5-mmots-2021-10-13-19-55). You can also clone the complete git tree
from:
The web is also available:
https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git/tag/?h=damon_reclaim/patches/v1
Sequence Of Patches
===================
The first patch makes DAMOS support the physical address space for the
page out action. Following five patches (patches 2-6) implement the
time/size quotas. Next four patches (patches 7-10) implement the memory
regions prioritization within the limit. Then, three following patches
(patches 11-13) implement the watermarks-based schemes activation.
Finally, the last two patches (patches 14-15) implement and document the
DAMON-based reclamation using the advanced DAMOS.
This makes the DAMON primitives for physical address space support the
pageout action for DAMON-based Operation Schemes. With this commit,
hence, users can easily implement system-level data access-aware
reclamations using DAMOS.
[sj@kernel.org: fix missing-prototype build warning] Link: https://lkml.kernel.org/r/20211025064220.13904-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211019150731.16699-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211019150731.16699-2-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: David Hildenbrand <david@redhat.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Marco Elver <elver@google.com> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Greg Thelen <gthelen@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: David Rientjes <rientjes@google.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rongwei Wang [Fri, 5 Nov 2021 20:47:09 +0000 (13:47 -0700)]
mm/damon/dbgfs: remove unnecessary variables
In some functions, it's unnecessary to declare 'err' and 'ret' variables
at the same time. This patch mainly to simplify the issue of such
declarations by reusing one variable.
Link: https://lkml.kernel.org/r/20211014073014.35754-1-sj@kernel.org Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com> Signed-off-by: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The only usage of these structs is to pass their addresses to
walk_page_range(), which takes a pointer to const mm_walk_ops as
argument. Make them const to allow the compiler to put them in
read-only memory.
SeongJae Park [Fri, 5 Nov 2021 20:47:00 +0000 (13:47 -0700)]
mm/damon/dbgfs: support physical memory monitoring
This makes the 'damon-dbgfs' to support the physical memory monitoring,
in addition to the virtual memory monitoring.
Users can do the physical memory monitoring by writing a special
keyword, 'paddr' to the 'target_ids' debugfs file. Then, DAMON will
check the special keyword and configure the monitoring context to run
with the primitives for the physical address space.
Unlike the virtual memory monitoring, the monitoring target region will
not be automatically set. Therefore, users should also set the
monitoring target address region using the 'init_regions' debugfs file.
Also, note that the physical memory monitoring will not automatically
terminated. The user should explicitly turn off the monitoring by
writing 'off' to the 'monitor_on' debugfs file.
Link: https://lkml.kernel.org/r/20211012205711.29216-7-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Brendan Higgins <brendanhiggins@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:46:56 +0000 (13:46 -0700)]
mm/damon: implement primitives for physical address space monitoring
This implements the monitoring primitives for the physical memory
address space. Internally, it uses the PTE Accessed bit, similar to
that of the virtual address spaces monitoring primitives. It supports
only user memory pages, as idle pages tracking does. If the monitoring
target physical memory address range contains non-user memory pages,
access check of the pages will do nothing but simply treat the pages as
not accessed.
Link: https://lkml.kernel.org/r/20211012205711.29216-6-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Brendan Higgins <brendanhiggins@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:46:53 +0000 (13:46 -0700)]
mm/damon/vaddr: separate commonly usable functions
This moves functions in the default virtual address spaces monitoring
primitives that commonly usable from other address spaces like physical
address space into a header file. Those will be reused by the physical
address space monitoring primitives which will be implemented by the
following commit.
[sj@kernel.org: include 'highmem.h' to fix a build failure] Link: https://lkml.kernel.org/r/20211014110848.5204-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211012205711.29216-5-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Brendan Higgins <brendanhiggins@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:46:42 +0000 (13:46 -0700)]
mm/damon/dbgfs: allow users to set initial monitoring target regions
Patch series "DAMON: Support Physical Memory Address Space Monitoring:.
DAMON currently supports only virtual address spaces monitoring. It can
be easily extended for various use cases and address spaces by
configuring its monitoring primitives layer to use appropriate
primitives implementations, though. This patchset implements monitoring
primitives for the physical address space monitoring using the
structure.
The first 3 patches allow the user space users manually set the
monitoring regions. The 1st patch implements the feature in the
'damon-dbgfs'. Then, patches for adding a unit tests (the 2nd patch)
and updating the documentation (the 3rd patch) follow.
Following 4 patches implement the physical address space monitoring
primitives. The 4th patch makes some primitive functions for the
virtual address spaces primitives reusable. The 5th patch implements
the physical address space monitoring primitives. The 6th patch links
the primitives to the 'damon-dbgfs'. Finally, 7th patch documents this
new features.
This patch (of 7):
Some 'damon-dbgfs' users would want to monitor only a part of the entire
virtual memory address space. The program interface users in the kernel
space could use '->before_start()' callback or set the regions inside
the context struct as they want, but 'damon-dbgfs' users cannot.
For that reason, this introduces a new debugfs file called
'init_region'. 'damon-dbgfs' users can specify which initial monitoring
target address regions they want by writing special input to the file.
The input should describe each region in each line in the below form:
<pid> <start address> <end address>
Note that the regions will be updated to cover entire memory mapped
regions after a 'regions update interval' is passed. If you want the
regions to not be updated after the initial setting, you could set the
interval as a very long time, say, a few decades.
Link: https://lkml.kernel.org/r/20211012205711.29216-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211012205711.29216-2-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: David Hildenbrand <david@redhat.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Marco Elver <elver@google.com> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Greg Thelen <gthelen@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: David Rienjes <rientjes@google.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Brendan Higgins <brendanhiggins@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:46:32 +0000 (13:46 -0700)]
mm/damon/schemes: implement statistics feature
To tune the DAMON-based operation schemes, knowing how many and how
large regions are affected by each of the schemes will be helful. Those
stats could be used for not only the tuning, but also monitoring of the
working set size and the number of regions, if the scheme does not
change the program behavior too much.
For the reason, this implements the statistics for the schemes. The
total number and size of the regions that each scheme is applied are
exported to users via '->stat_count' and '->stat_sz' of 'struct damos'.
Admins can also check the number by reading 'schemes' debugfs file. The
last two integers now represents the stats. To allow collecting the
stats without changing the program behavior, this also adds new scheme
action, 'DAMOS_STAT'. Note that 'DAMOS_STAT' is not only making no
memory operation actions, but also does not reset the age of regions.
Link: https://lkml.kernel.org/r/20211001125604.29660-6-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:46:29 +0000 (13:46 -0700)]
mm/damon/dbgfs: support DAMON-based Operation Schemes
This makes 'damon-dbgfs' to support the data access monitoring oriented
memory management schemes. Users can read and update the schemes using
``<debugfs>/damon/schemes`` file. The format is::
SeongJae Park [Fri, 5 Nov 2021 20:46:25 +0000 (13:46 -0700)]
mm/damon/vaddr: support DAMON-based Operation Schemes
This makes DAMON's default primitives for virtual address spaces to
support DAMON-based Operation Schemes (DAMOS) by implementing actions
application functions and registering it to the monitoring context. The
implementation simply links 'madvise()' for related DAMOS actions. That
is, 'madvise(MADV_WILLNEED)' is called for 'WILLNEED' DAMOS action and
similar for other actions ('COLD', 'PAGEOUT', 'HUGEPAGE', 'NOHUGEPAGE').
So, the kernel space DAMON users can now use the DAMON-based
optimizations with only small amount of code.
Link: https://lkml.kernel.org/r/20211001125604.29660-4-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In many cases, users might use DAMON for simple data access aware memory
management optimizations such as applying an operation scheme to a
memory region of a specific size having a specific access frequency for
a specific time. For example, "page out a memory region larger than 100
MiB but having a low access frequency more than 10 minutes", or "Use THP
for a memory region larger than 2 MiB having a high access frequency for
more than 2 seconds".
Most simple form of the solution would be doing offline data access
pattern profiling using DAMON and modifying the application source code
or system configuration based on the profiling results. Or, developing
a daemon constructed with two modules (one for access monitoring and the
other for applying memory management actions via mlock(), madvise(),
sysctl, etc) is imaginable.
To avoid users spending their time for implementation of such simple
data access monitoring-based operation schemes, this makes DAMON to
handle such schemes directly. With this change, users can simply
specify their desired schemes to DAMON. Then, DAMON will automatically
apply the schemes to the user-specified target processes.
Each of the schemes is composed with conditions for filtering of the
target memory regions and desired memory management action for the
target. Specifically, the format is::
The filtering conditions are size of memory region, number of accesses
to the region monitored by DAMON, and the age of the region. The age of
region is incremented periodically but reset when its addresses or
access frequency has significantly changed or the action of a scheme was
applied. For the action, current implementation supports a few of
madvise()-like hints, ``WILLNEED``, ``COLD``, ``PAGEOUT``, ``HUGEPAGE``,
and ``NOHUGEPAGE``.
Because DAMON supports various address spaces and application of the
actions to a monitoring target region is dependent to the type of the
target address space, the application code should be implemented by each
primitives and registered to the framework. Note that this only
implements the framework part. Following commit will implement the
action applications for virtual address spaces primitives.
Link: https://lkml.kernel.org/r/20211001125604.29660-3-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Hildenbrand <david@redhat.com> Cc: David Rienjes <rientjes@google.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Greg Thelen <gthelen@google.com> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Marco Elver <elver@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:46:18 +0000 (13:46 -0700)]
mm/damon/core: account age of target regions
Patch series "Implement Data Access Monitoring-based Memory Operation Schemes".
Introduction
============
DAMON[1] can be used as a primitive for data access aware memory
management optimizations. For that, users who want such optimizations
should run DAMON, read the monitoring results, analyze it, plan a new
memory management scheme, and apply the new scheme by themselves. Such
efforts will be inevitable for some complicated optimizations.
However, in many other cases, the users would simply want the system to
apply a memory management action to a memory region of a specific size
having a specific access frequency for a specific time. For example,
"page out a memory region larger than 100 MiB keeping only rare accesses
more than 2 minutes", or "Do not use THP for a memory region larger than
2 MiB rarely accessed for more than 1 seconds".
To make the works easier and non-redundant, this patchset implements a
new feature of DAMON, which is called Data Access Monitoring-based
Operation Schemes (DAMOS). Using the feature, users can describe the
normal schemes in a simple way and ask DAMON to execute those on its
own.
[1] https://damonitor.github.io
Evaluations
===========
DAMOS is accurate and useful for memory management optimizations. An
experimental DAMON-based operation scheme for THP, 'ethp', removes
76.15% of THP memory overheads while preserving 51.25% of THP speedup.
Another experimental DAMON-based 'proactive reclamation' implementation,
'prcl', reduces 93.38% of residential sets and 23.63% of system memory
footprint while incurring only 1.22% runtime overhead in the best case
(parsec3/freqmine).
NOTE that the experimental THP optimization and proactive reclamation
are not for production but only for proof of concepts.
Please refer to the showcase web site's evaluation document[1] for
detailed evaluation setup and results.
For people who want to test DAMON but using LTS kernels, there are
another couple of trees based on two latest LTS kernels respectively and
containing the 'damon/master' backports.
- For v5.4.y: https://git.kernel.org/sj/h/damon/for-v5.4.y
- For v5.10.y: https://git.kernel.org/sj/h/damon/for-v5.10.y
Sequence Of Patches
===================
The 1st patch accounts age of each region. The 2nd patch implements the
core of the DAMON-based operation schemes feature. The 3rd patch makes
the default monitoring primitives for virtual address spaces to support
the schemes. From this point, the kernel space users can use DAMOS.
The 4th patch exports the feature to the user space via the debugfs
interface. The 5th patch implements schemes statistics feature for
easier tuning of the schemes and runtime access pattern analysis, and
the 6th patch adds selftests for these changes. Finally, the 7th patch
documents this new feature.
This patch (of 7):
DAMON can be used for data access pattern aware memory management
optimizations. For that, users should run DAMON, read the monitoring
results, analyze it, plan a new memory management scheme, and apply the
new scheme by themselves. It would not be too hard, but still require
some level of effort. For complicated cases, this effort is inevitable.
That said, in many cases, users would simply want to apply an actions to
a memory region of a specific size having a specific access frequency
for a specific time. For example, "page out a memory region larger than
100 MiB but having a low access frequency more than 10 minutes", or "Use
THP for a memory region larger than 2 MiB having a high access frequency
for more than 2 seconds".
For such optimizations, users will need to first account the age of each
region themselves. To reduce such efforts, this implements a simple age
account of each region in DAMON. For each aggregation step, DAMON
compares the access frequency with that from last aggregation and reset
the age of the region if the change is significant. Else, the age is
incremented. Also, in case of the merge of regions, the region
size-weighted average of the ages is set as the age of merged new
region.
Link: https://lkml.kernel.org/r/20211001125604.29660-1-sj@kernel.org Link: https://lkml.kernel.org/r/20211001125604.29660-2-sj@kernel.org Signed-off-by: SeongJae Park <sj@kernel.org> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Amit Shah <amit@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: David Hildenbrand <david@redhat.com> Cc: David Woodhouse <dwmw@amazon.com> Cc: Marco Elver <elver@google.com> Cc: Leonard Foerster <foersleo@amazon.de> Cc: Greg Thelen <gthelen@google.com> Cc: Markus Boehme <markubo@amazon.de> Cc: David Rienjes <rientjes@google.com> Cc: Shakeel Butt <shakeelb@google.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Colin Ian King [Fri, 5 Nov 2021 20:46:15 +0000 (13:46 -0700)]
mm/damon/core: nullify pointer ctx->kdamond with a NULL
Currently a plain integer is being used to nullify the pointer
ctx->kdamond. Use NULL instead. Cleans up sparse warning:
mm/damon/core.c:317:40: warning: Using plain integer as NULL pointer
Link: https://lkml.kernel.org/r/20210925215908.181226-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Reviewed-by: SeongJae Park <sj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
SeongJae Park [Fri, 5 Nov 2021 20:45:55 +0000 (13:45 -0700)]
Documentation/vm: move user guides to admin-guide/mm/
Most memory management user guide documents are in 'admin-guide/mm/',
but two of those are in 'vm/'. This moves the two docs into
'admin-guide/mm' for easier documents finding.
Marco Elver [Fri, 5 Nov 2021 20:45:49 +0000 (13:45 -0700)]
kfence: default to dynamic branch instead of static keys mode
We have observed that on very large machines with newer CPUs, the static
key/branch switching delay is on the order of milliseconds. This is due
to the required broadcast IPIs, which simply does not scale well to
hundreds of CPUs (cores). If done too frequently, this can adversely
affect tail latencies of various workloads.
One workaround is to increase the sample interval to several seconds,
while decreasing sampled allocation coverage, but the problem still
exists and could still increase tail latencies.
As already noted in the Kconfig help text, there are trade-offs: at
lower sample intervals the dynamic branch results in better performance;
however, at very large sample intervals, the static keys mode can result
in better performance -- careful benchmarking is recommended.
Our initial benchmarking showed that with large enough sample intervals
and workloads stressing the allocator, the static keys mode was slightly
better. Evaluating and observing the possible system-wide side-effects
of the static-key-switching induced broadcast IPIs, however, was a blind
spot (in particular on large machines with 100s of cores).
Therefore, a major downside of the static keys mode is, unfortunately,
that it is hard to predict performance on new system architectures and
topologies, but also making conclusions about performance of new
workloads based on a limited set of benchmarks.
Most distributions will simply select the defaults, while targeting a
large variety of different workloads and system architectures. As such,
the better default is CONFIG_KFENCE_STATIC_KEYS=n, and re-enabling it is
only recommended after careful evaluation.
For reference, on x86-64 the condition in kfence_alloc() generates
exactly
2 instructions in the kmem_cache_alloc() fast-path:
Marco Elver [Fri, 5 Nov 2021 20:45:46 +0000 (13:45 -0700)]
kfence: always use static branches to guard kfence_alloc()
Regardless of KFENCE mode (CONFIG_KFENCE_STATIC_KEYS: either using
static keys to gate allocations, or using a simple dynamic branch),
always use a static branch to avoid the dynamic branch in kfence_alloc()
if KFENCE was disabled at boot.
For CONFIG_KFENCE_STATIC_KEYS=n, this now avoids the dynamic branch if
KFENCE was disabled at boot.
To simplify, also unifies the location where kfence_allocation_gate is
read-checked to just be inline in kfence_alloc().
Link: https://lkml.kernel.org/r/20211019102524.2807208-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Marco Elver [Fri, 5 Nov 2021 20:45:43 +0000 (13:45 -0700)]
kfence: shorten critical sections of alloc/free
Initializing memory and setting/checking the canary bytes is relatively
expensive, and doing so in the meta->lock critical sections extends the
duration with preemption and interrupts disabled unnecessarily.
Any reads to meta->addr and meta->size in kfence_guarded_alloc() and
kfence_guarded_free() don't require locking meta->lock as long as the
object is removed from the freelist: only kfence_guarded_alloc() sets
meta->addr and meta->size after removing it from the freelist, which
requires a preceding kfence_guarded_free() returning it to the list or
the initial state.
Therefore move reads to meta->addr and meta->size, including expensive
memory initialization using them, out of meta->lock critical sections.
Link: https://lkml.kernel.org/r/20210930153706.2105471-1-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Acked-by: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Jann Horn <jannh@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Marco Elver [Fri, 5 Nov 2021 20:45:37 +0000 (13:45 -0700)]
kfence: add note to documentation about skipping covered allocations
Add a note briefly mentioning the new policy about "skipping currently
covered allocations if pool close to full." Since this has a notable
impact on KFENCE's bug-detection ability on systems with large uptimes,
it is worth pointing out the feature.
Link: https://lkml.kernel.org/r/20210923104803.2620285-5-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Alexander Potapenko <glider@google.com> Cc: Aleksandr Nogikh <nogikh@google.com> Cc: Jann Horn <jannh@google.com> Cc: Taras Madan <tarasmadan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Marco Elver [Fri, 5 Nov 2021 20:45:34 +0000 (13:45 -0700)]
kfence: limit currently covered allocations when pool nearly full
One of KFENCE's main design principles is that with increasing uptime,
allocation coverage increases sufficiently to detect previously
undetected bugs.
We have observed that frequent long-lived allocations of the same source
(e.g. pagecache) tend to permanently fill up the KFENCE pool with
increasing system uptime, thus breaking the above requirement. The
workaround thus far had been increasing the sample interval and/or
increasing the KFENCE pool size, but is no reliable solution.
To ensure diverse coverage of allocations, limit currently covered
allocations of the same source once pool utilization reaches 75%
(configurable via `kfence.skip_covered_thresh`) or above. The effect is
retaining reasonable allocation coverage when the pool is close to full.
A side-effect is that this also limits frequent long-lived allocations
of the same source filling up the pool permanently.
Uniqueness of an allocation for coverage purposes is based on its
(partial) allocation stack trace (the source). A Counting Bloom filter
is used to check if an allocation is covered; if the allocation is
currently covered, the allocation is skipped by KFENCE.
Testing was done using:
(a) a synthetic workload that performs frequent long-lived
allocations (default config values; sample_interval=1;
num_objects=63), and
(b) normal desktop workloads on an otherwise idle machine where
the problem was first reported after a few days of uptime
(default config values).
In both test cases the sampled allocation rate no longer drops to zero
at any point. In the case of (b) we observe (after 2 days uptime) 15%
unique allocations in the pool, 77% pool utilization, with 20% "skipped
allocations (covered)".
Marco Elver [Fri, 5 Nov 2021 20:45:31 +0000 (13:45 -0700)]
kfence: move saving stack trace of allocations into __kfence_alloc()
Move the saving of the stack trace of allocations into __kfence_alloc(),
so that the stack entries array can be used outside of
kfence_guarded_alloc() and we avoid potentially unwinding the stack
multiple times.
Link: https://lkml.kernel.org/r/20210923104803.2620285-3-elver@google.com Signed-off-by: Marco Elver <elver@google.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Acked-by: Alexander Potapenko <glider@google.com> Cc: Aleksandr Nogikh <nogikh@google.com> Cc: Jann Horn <jannh@google.com> Cc: Taras Madan <tarasmadan@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
projects / kernel.git / log