selftests/vm: gup_test: test faulting in kernel, and verify pinnable pages

When pages are pinned they can be faulted in userland and migrated, and
they can be faulted right in kernel without migration.

In either case, the pinned pages must end-up being pinnable (not
movable).

Add a new test to gup_test, to help verify that the gup/pup
(get_user_pages() / pin_user_pages()) behavior with respect to pinnable
and movable pages is reasonable and correct.  Specifically, provide a
way to:

1) Verify that only "pinnable" pages are pinned.  This is checked
   automatically for you.

2) Verify that gup/pup performance is reasonable.  This requires
   comparing benchmarks between doing gup/pup on pages that have been
   pre-faulted in from user space, vs.  doing gup/pup on pages that are
   not faulted in until gup/pup time (via FOLL_TOUCH).  This decision is
   controlled with the new -z command line option.

Link: https://lkml.kernel.org/r/20210215161349.246722-15-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/gup_test.c b/mm/gup_test.c
index a6ed1c877679ee61eedd3bf616dcb2af543db9c1..d974dec19e1caba90ce5fd87678b3f73e8d0082d 100644 (file)
--- a/mm/gup_test.c
+++ b/mm/gup_test.c
@@ -52,6 +52,12 @@ static void verify_dma_pinned(unsigned int cmd, struct page **pages,
 
                                dump_page(page, "gup_test failure");
                                break;
+                       } else if (cmd == PIN_LONGTERM_BENCHMARK &&
+                               WARN(!is_pinnable_page(page),
+                                    "pages[%lu] is NOT pinnable but pinned\n",
+                                    i)) {
+                               dump_page(page, "gup_test failure");
+                               break;
                        }
                }
                break;

diff --git a/tools/testing/selftests/vm/gup_test.c b/tools/testing/selftests/vm/gup_test.c
index 943cc2608dc2101791722cd6230c2dad6693eed6..1e662d59c502a806cb0bf8f7983a19f7663f9625 100644 (file)
--- a/tools/testing/selftests/vm/gup_test.c
+++ b/tools/testing/selftests/vm/gup_test.c
@@ -13,6 +13,7 @@
 
 /* Just the flags we need, copied from mm.h: */
 #define FOLL_WRITE     0x01    /* check pte is writable */
+#define FOLL_TOUCH     0x02    /* mark page accessed */
 
 static char *cmd_to_str(unsigned long cmd)
 {
@@ -39,11 +40,11 @@ int main(int argc, char **argv)
        unsigned long size = 128 * MB;
        int i, fd, filed, opt, nr_pages = 1, thp = -1, repeats = 1, write = 1;
        unsigned long cmd = GUP_FAST_BENCHMARK;
-       int flags = MAP_PRIVATE;
+       int flags = MAP_PRIVATE, touch = 0;
        char *file = "/dev/zero";
        char *p;
 
-       while ((opt = getopt(argc, argv, "m:r:n:F:f:abctTLUuwWSHp")) != -1) {
+       while ((opt = getopt(argc, argv, "m:r:n:F:f:abctTLUuwWSHpz")) != -1) {
                switch (opt) {
                case 'a':
                        cmd = PIN_FAST_BENCHMARK;
@@ -110,6 +111,10 @@ int main(int argc, char **argv)
                case 'H':
                        flags |= (MAP_HUGETLB | MAP_ANONYMOUS);
                        break;
+               case 'z':
+                       /* fault pages in gup, do not fault in userland */
+                       touch = 1;
+                       break;
                default:
                        return -1;
                }
@@ -167,8 +172,18 @@ int main(int argc, char **argv)
        else if (thp == 0)
                madvise(p, size, MADV_NOHUGEPAGE);
 
-       for (; (unsigned long)p < gup.addr + size; p += PAGE_SIZE)
-               p[0] = 0;
+       /*
+        * FOLL_TOUCH, in gup_test, is used as an either/or case: either
+        * fault pages in from the kernel via FOLL_TOUCH, or fault them
+        * in here, from user space. This allows comparison of performance
+        * between those two cases.
+        */
+       if (touch) {
+               gup.gup_flags |= FOLL_TOUCH;
+       } else {
+               for (; (unsigned long)p < gup.addr + size; p += PAGE_SIZE)
+                       p[0] = 0;
+       }
 
        /* Only report timing information on the *_BENCHMARK commands: */
        if ((cmd == PIN_FAST_BENCHMARK) || (cmd == GUP_FAST_BENCHMARK) ||