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selftests: add zswapin and no zswap tests

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Add a selftest to cover the zswapin code path, allocating more memory than
the cgroup limit to trigger swapout/zswapout, then reading the pages back
in memory several times.  This is inspired by a recently encountered
kernel crash on the zswapin path in our internal kernel, which went
undetected because of a lack of test coverage for this path.

Add a selftest to verify that when memory.zswap.max = 0, no pages can go
to the zswap pool for the cgroup.

[nphamcs@gmail.com: remove redundant comment, add success checks]
  Link: https://lkml.kernel.org/r/20240222043132.616320-1-nphamcs@gmail.com
Link: https://lkml.kernel.org/r/20240205225608.3083251-4-nphamcs@gmail.com
Signed-off-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Rik van Riel <riel@surriel.com>
Suggested-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Nhat Pham 2024-02-05 14:56:08 -08:00 committed by Andrew Morton
parent 012688f600
commit b93c28ff72
1 changed files with 118 additions and 2 deletions
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120
tools/testing/selftests/cgroup/test_zswap.c
View file

@ -60,6 +60,27 @@ static long get_zswpout(const char *cgroup)
return cg_read_key_long(cgroup, "memory.stat", "zswpout ");
}
static int allocate_and_read_bytes(const char *cgroup, void *arg)
{
size_t size = (size_t)arg;
char *mem = (char *)malloc(size);
int ret = 0;
if (!mem)
return -1;
for (int i = 0; i < size; i += 4095)
mem[i] = 'a';
/* Go through the allocated memory to (z)swap in and out pages */
for (int i = 0; i < size; i += 4095) {
if (mem[i] != 'a')
ret = -1;
}
free(mem);
return ret;
}
static int allocate_bytes(const char *cgroup, void *arg)
{
size_t size = (size_t)arg;
@ -100,7 +121,6 @@ static int test_zswap_usage(const char *root)
int ret = KSFT_FAIL;
char *test_group;
/* Set up */
test_group = cg_name(root, "no_shrink_test");
if (!test_group)
goto out;
@ -133,6 +153,101 @@ static int test_zswap_usage(const char *root)
return ret;
}
/*
* Check that when memory.zswap.max = 0, no pages can go to the zswap pool for
* the cgroup.
*/
static int test_swapin_nozswap(const char *root)
{
int ret = KSFT_FAIL;
char *test_group;
long swap_peak, zswpout;
test_group = cg_name(root, "no_zswap_test");
if (!test_group)
goto out;
if (cg_create(test_group))
goto out;
if (cg_write(test_group, "memory.max", "8M"))
goto out;
if (cg_write(test_group, "memory.zswap.max", "0"))
goto out;
/* Allocate and read more than memory.max to trigger swapin */
if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
goto out;
/* Verify that pages are swapped out, but no zswap happened */
swap_peak = cg_read_long(test_group, "memory.swap.peak");
if (swap_peak < 0) {
ksft_print_msg("failed to get cgroup's swap_peak\n");
goto out;
}
if (swap_peak < MB(24)) {
ksft_print_msg("at least 24MB of memory should be swapped out\n");
goto out;
}
zswpout = get_zswpout(test_group);
if (zswpout < 0) {
ksft_print_msg("failed to get zswpout\n");
goto out;
}
if (zswpout > 0) {
ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n");
goto out;
}
ret = KSFT_PASS;
out:
cg_destroy(test_group);
free(test_group);
return ret;
}
/* Simple test to verify the (z)swapin code paths */
static int test_zswapin(const char *root)
{
int ret = KSFT_FAIL;
char *test_group;
long zswpin;
test_group = cg_name(root, "zswapin_test");
if (!test_group)
goto out;
if (cg_create(test_group))
goto out;
if (cg_write(test_group, "memory.max", "8M"))
goto out;
if (cg_write(test_group, "memory.zswap.max", "max"))
goto out;
/* Allocate and read more than memory.max to trigger (z)swap in */
if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
goto out;
zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin ");
if (zswpin < 0) {
ksft_print_msg("failed to get zswpin\n");
goto out;
}
if (zswpin < MB(24) / PAGE_SIZE) {
ksft_print_msg("at least 24MB should be brought back from zswap\n");
goto out;
}
ret = KSFT_PASS;
out:
cg_destroy(test_group);
free(test_group);
return ret;
}
/*
* When trying to store a memcg page in zswap, if the memcg hits its memory
* limit in zswap, writeback should affect only the zswapped pages of that
@ -144,7 +259,6 @@ static int test_no_invasive_cgroup_shrink(const char *root)
size_t control_allocation_size = MB(10);
char *control_allocation, *wb_group = NULL, *control_group = NULL;
/* Set up */
wb_group = setup_test_group_1M(root, "per_memcg_wb_test1");
if (!wb_group)
return KSFT_FAIL;
@ -309,6 +423,8 @@ struct zswap_test {
const char *name;
} tests[] = {
T(test_zswap_usage),
T(test_swapin_nozswap),
T(test_zswapin),
T(test_no_kmem_bypass),
T(test_no_invasive_cgroup_shrink),
};