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selftests/vm: add file/shmem MADV_COLLAPSE selftest for cleared pmd

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This test tests that MADV_COLLAPSE acting on file/shmem memory for which
(1) the file extent mapping by the memory is already a huge page in the
page cache, and (2) the pmd mapping this memory in the target process is
none.

In practice, (1)+(2) is the state left over after khugepaged has
successfully collapsed file/shmem memory for a target VMA, but the memory
has not yet been refaulted.  So, this test in-effect tests MADV_COLLAPSE
racing with khugepaged to collapse the memory first.

Link: https://lkml.kernel.org/r/20220907144521.3115321-10-zokeefe@google.com
Link: https://lkml.kernel.org/r/20220922224046.1143204-10-zokeefe@google.com
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zach O'Keefe 2022-09-22 15:40:45 -07:00 committed by Andrew Morton
parent d0d35b6010
commit 69d9428ce9
1 changed files with 30 additions and 0 deletions
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30
tools/testing/selftests/vm/khugepaged.c
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@ -1353,6 +1353,33 @@ static void madvise_collapse_existing_thps(struct collapse_context *c,
ops->cleanup_area(p, hpage_pmd_size);
}
/*
* Test race with khugepaged where page tables have been retracted and
* pmd cleared.
*/
static void madvise_retracted_page_tables(struct collapse_context *c,
struct mem_ops *ops)
{
void *p;
int nr_hpages = 1;
unsigned long size = nr_hpages * hpage_pmd_size;
p = ops->setup_area(nr_hpages);
ops->fault(p, 0, size);
/* Let khugepaged collapse and leave pmd cleared */
if (wait_for_scan("Collapse and leave PMD cleared", p, nr_hpages,
ops)) {
fail("Timeout");
return;
}
success("OK");
c->collapse("Install huge PMD from page cache", p, nr_hpages, ops,
true);
validate_memory(p, 0, size);
ops->cleanup_area(p, size);
}
static void usage(void)
{
fprintf(stderr, "\nUsage: ./khugepaged <test type> [dir]\n\n");
@ -1524,5 +1551,8 @@ int main(int argc, const char **argv)
TEST(madvise_collapse_existing_thps, madvise_context, file_ops);
TEST(madvise_collapse_existing_thps, madvise_context, shmem_ops);
TEST(madvise_retracted_page_tables, madvise_context, file_ops);
TEST(madvise_retracted_page_tables, madvise_context, shmem_ops);
restore_settings(0);
}