For now, the feature of hugetlb_free_vmemmap is not compatible with the
feature of memory_hotplug.memmap_on_memory, and hugetlb_free_vmemmap takes
precedence over memory_hotplug.memmap_on_memory. However, someone wants
to make memory_hotplug.memmap_on_memory takes precedence over
hugetlb_free_vmemmap since memmap_on_memory makes it more likely to
succeed memory hotplug in close-to-OOM situations. So the decision of
making hugetlb_free_vmemmap take precedence is not wise and elegant.
The proper approach is to have hugetlb_vmemmap.c do the check whether the
section which the HugeTLB pages belong to can be optimized. If the
section's vmemmap pages are allocated from the added memory block itself,
hugetlb_free_vmemmap should refuse to optimize the vmemmap, otherwise, do
the optimization. Then both kernel parameters are compatible. So this
patch introduces VmemmapSelfHosted to mask any non-optimizable vmemmap
pages. The hugetlb_vmemmap can use this flag to detect if a vmemmap page
can be optimized.
[songmuchun@bytedance.com: walk vmemmap page tables to avoid false-positive]
Link: https://lkml.kernel.org/r/20220620110616.12056-3-songmuchun@bytedance.com
Link: https://lkml.kernel.org/r/20220617135650.74901-3-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Co-developed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
the default is on.
- This is not compatible with memory_hotplug.memmap_on_memory.
- If both parameters are enabled, hugetlb_free_vmemmap takes
- precedence over memory_hotplug.memmap_on_memory.
+ Note that the vmemmap pages may be allocated from the added
+ memory block itself when memory_hotplug.memmap_on_memory is
+ enabled, those vmemmap pages cannot be optimized even if this
+ feature is enabled. Other vmemmap pages not allocated from
+ the added memory block itself do not be affected.
hung_task_panic=
[KNL] Should the hung task detector generate panics.
[KNL,X86,ARM] Boolean flag to enable this feature.
Format: {on | off (default)}
When enabled, runtime hotplugged memory will
- allocate its internal metadata (struct pages)
- from the hotadded memory which will allow to
- hotadd a lot of memory without requiring
- additional memory to do so.
+ allocate its internal metadata (struct pages,
+ those vmemmap pages cannot be optimized even
+ if hugetlb_free_vmemmap is enabled) from the
+ hotadded memory which will allow to hotadd a
+ lot of memory without requiring additional
+ memory to do so.
This feature is disabled by default because it
has some implication on large (e.g. GB)
allocations in some configurations (e.g. small
Note that even when enabled, there are a few cases where
the feature is not effective.
- This is not compatible with hugetlb_free_vmemmap. If
- both parameters are enabled, hugetlb_free_vmemmap takes
- precedence over memory_hotplug.memmap_on_memory.
-
memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
Format: <integer>
default : 0 <disable>
hugetlb_optimize_vmemmap
========================
-This knob is not available when memory_hotplug.memmap_on_memory (kernel parameter)
-is configured or the size of 'struct page' (a structure defined in
-include/linux/mm_types.h) is not power of two (an unusual system config could
+This knob is not available when the size of 'struct page' (a structure defined
+in include/linux/mm_types.h) is not power of two (an unusual system config could
result in this).
Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages
extern bool mhp_supports_memmap_on_memory(unsigned long size);
#endif /* CONFIG_MEMORY_HOTPLUG */
-#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
-bool mhp_memmap_on_memory(void);
-#else
-static inline bool mhp_memmap_on_memory(void)
-{
- return false;
-}
-#endif
-
#endif /* __LINUX_MEMORY_HOTPLUG_H */
/* Only valid for buddy pages. Used to track pages that are reported */
PG_reported = PG_uptodate,
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+ /* For self-hosted memmap pages */
+ PG_vmemmap_self_hosted = PG_owner_priv_1,
+#endif
};
#define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1)
*/
__PAGEFLAG(Reported, reported, PF_NO_COMPOUND)
+#ifdef CONFIG_MEMORY_HOTPLUG
+PAGEFLAG(VmemmapSelfHosted, vmemmap_self_hosted, PF_ANY)
+#else
+PAGEFLAG_FALSE(VmemmapSelfHosted, vmemmap_self_hosted)
+#endif
+
/*
* On an anonymous page mapped into a user virtual memory area,
* page->mapping points to its anon_vma, not to a struct address_space;
*/
#define pr_fmt(fmt) "HugeTLB: " fmt
-#include <linux/memory_hotplug.h>
+#include <linux/memory.h>
#include "hugetlb_vmemmap.h"
/*
return ret;
}
+static unsigned int vmemmap_optimizable_pages(struct hstate *h,
+ struct page *head)
+{
+ if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
+ return 0;
+
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) {
+ pmd_t *pmdp, pmd;
+ struct page *vmemmap_page;
+ unsigned long vaddr = (unsigned long)head;
+
+ /*
+ * Only the vmemmap page's vmemmap page can be self-hosted.
+ * Walking the page tables to find the backing page of the
+ * vmemmap page.
+ */
+ pmdp = pmd_off_k(vaddr);
+ /*
+ * The READ_ONCE() is used to stabilize *pmdp in a register or
+ * on the stack so that it will stop changing under the code.
+ * The only concurrent operation where it can be changed is
+ * split_vmemmap_huge_pmd() (*pmdp will be stable after this
+ * operation).
+ */
+ pmd = READ_ONCE(*pmdp);
+ if (pmd_leaf(pmd))
+ vmemmap_page = pmd_page(pmd) + pte_index(vaddr);
+ else
+ vmemmap_page = pte_page(*pte_offset_kernel(pmdp, vaddr));
+ /*
+ * Due to HugeTLB alignment requirements and the vmemmap pages
+ * being at the start of the hotplugged memory region in
+ * memory_hotplug.memmap_on_memory case. Checking any vmemmap
+ * page's vmemmap page if it is marked as VmemmapSelfHosted is
+ * sufficient.
+ *
+ * [ hotplugged memory ]
+ * [ section ][...][ section ]
+ * [ vmemmap ][ usable memory ]
+ * ^ | | |
+ * +---+ | |
+ * ^ | |
+ * +-------+ |
+ * ^ |
+ * +-------------------------------------------+
+ */
+ if (PageVmemmapSelfHosted(vmemmap_page))
+ return 0;
+ }
+
+ return hugetlb_optimize_vmemmap_pages(h);
+}
+
void hugetlb_vmemmap_free(struct hstate *h, struct page *head)
{
unsigned long vmemmap_addr = (unsigned long)head;
unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages;
- vmemmap_pages = hugetlb_optimize_vmemmap_pages(h);
+ vmemmap_pages = vmemmap_optimizable_pages(h, head);
if (!vmemmap_pages)
return;
- if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF)
- return;
-
static_branch_inc(&hugetlb_optimize_vmemmap_key);
vmemmap_addr += RESERVE_VMEMMAP_SIZE;
static __init int hugetlb_vmemmap_sysctls_init(void)
{
/*
- * If "memory_hotplug.memmap_on_memory" is enabled or "struct page"
- * crosses page boundaries, the vmemmap pages cannot be optimized.
+ * If "struct page" crosses page boundaries, the vmemmap pages cannot
+ * be optimized.
*/
- if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page)))
+ if (is_power_of_2(sizeof(struct page)))
register_sysctl_init("vm", hugetlb_vmemmap_sysctls);
return 0;
#include "shuffle.h"
#ifdef CONFIG_MHP_MEMMAP_ON_MEMORY
-static int memmap_on_memory_set(const char *val, const struct kernel_param *kp)
-{
- if (hugetlb_optimize_vmemmap_enabled())
- return 0;
- return param_set_bool(val, kp);
-}
-
-static const struct kernel_param_ops memmap_on_memory_ops = {
- .flags = KERNEL_PARAM_OPS_FL_NOARG,
- .set = memmap_on_memory_set,
- .get = param_get_bool,
-};
-
/*
* memory_hotplug.memmap_on_memory parameter
*/
static bool memmap_on_memory __ro_after_init;
-module_param_cb(memmap_on_memory, &memmap_on_memory_ops, &memmap_on_memory, 0444);
+module_param(memmap_on_memory, bool, 0444);
MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug");
-bool mhp_memmap_on_memory(void)
+static inline bool mhp_memmap_on_memory(void)
{
return memmap_on_memory;
}
+#else
+static inline bool mhp_memmap_on_memory(void)
+{
+ return false;
+}
#endif
enum {
struct zone *zone)
{
unsigned long end_pfn = pfn + nr_pages;
- int ret;
+ int ret, i;
ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages));
if (ret)
move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE);
+ for (i = 0; i < nr_pages; i++)
+ SetPageVmemmapSelfHosted(pfn_to_page(pfn + i));
+
/*
* It might be that the vmemmap_pages fully span sections. If that is
* the case, mark those sections online here as otherwise they will be
projects / kernel.git / commitdiff