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selftest/mm: ksm_functional_tests: test in mmap_and_merge_range() if anything got merged

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Let's extend mmap_and_merge_range() to test if anything in the current
process was merged. range_maps_duplicates() is too unreliable for that
use case, so instead look at KSM stats.

Trigger a complete unmerge first, to cleanup the stable tree and
stabilize accounting of merged pages.

Note that we're using /proc/self/ksm_merging_pages instead of
/proc/self/ksm_stat, because that one is available in more existing
kernels.

If /proc/self/ksm_merging_pages can't be opened, we can't perform any
checks and simply skip them.

We have to special-case the shared zeropage for now. But the only user
-- test_unmerge_zero_pages() -- performs its own merge checks.

Link: https://lkml.kernel.org/r/20230803143208.383663-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Peter Xu <peterx@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: liubo <liubo254@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2023-08-03 16:32:07 +02:00 committed by Andrew Morton
parent 14fb1fd751
commit 42096aa24b
1 changed files with 47 additions and 0 deletions
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47
tools/testing/selftests/mm/ksm_functional_tests.c
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@ -30,6 +30,7 @@
static int ksm_fd;
static int ksm_full_scans_fd;
static int proc_self_ksm_stat_fd;
static int proc_self_ksm_merging_pages_fd;
static int ksm_use_zero_pages_fd;
static int pagemap_fd;
static size_t pagesize;
@ -88,6 +89,22 @@ static long get_my_ksm_zero_pages(void)
return my_ksm_zero_pages;
}
static long get_my_merging_pages(void)
{
char buf[10];
ssize_t ret;
if (proc_self_ksm_merging_pages_fd < 0)
return proc_self_ksm_merging_pages_fd;
ret = pread(proc_self_ksm_merging_pages_fd, buf, sizeof(buf) - 1, 0);
if (ret <= 0)
return -errno;
buf[ret] = 0;
return strtol(buf, NULL, 10);
}
static long ksm_get_full_scans(void)
{
char buf[10];
@ -120,11 +137,29 @@ static int ksm_merge(void)
return 0;
}
static int ksm_unmerge(void)
{
if (write(ksm_fd, "2", 1) != 1)
return -errno;
return 0;
}
static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl)
{
char *map;
int ret;
/* Stabilize accounting by disabling KSM completely. */
if (ksm_unmerge()) {
ksft_test_result_fail("Disabling (unmerging) KSM failed\n");
goto unmap;
}
if (get_my_merging_pages() > 0) {
ksft_test_result_fail("Still pages merged\n");
goto unmap;
}
map = mmap(NULL, size, PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANON, -1, 0);
if (map == MAP_FAILED) {
@ -160,6 +195,16 @@ static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl)
ksft_test_result_fail("Running KSM failed\n");
goto unmap;
}
/*
* Check if anything was merged at all. Ignore the zero page that is
* accounted differently (depending on kernel support).
*/
if (val && !get_my_merging_pages()) {
ksft_test_result_fail("No pages got merged\n");
goto unmap;
}
return map;
unmap:
munmap(map, size);
@ -473,6 +518,8 @@ int main(int argc, char **argv)
if (pagemap_fd < 0)
ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
proc_self_ksm_stat_fd = open("/proc/self/ksm_stat", O_RDONLY);
proc_self_ksm_merging_pages_fd = open("/proc/self/ksm_merging_pages",
O_RDONLY);
ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
test_unmerge();