Commit a697dc2b authored by Domenico Cerasuolo's avatar Domenico Cerasuolo Committed by Andrew Morton
Browse files

selftests: cgroup: update per-memcg zswap writeback selftest 

The memcg-zswap self test is updated to adjust to the behavior change
implemented by commit 87730b165089 ("zswap: make shrinking memcg-aware"),
where zswap performs writeback for specific memcg.

Link: https://lkml.kernel.org/r/20231130194023.4102148-6-nphamcs@gmail.com


Signed-off-by: default avatarDomenico Cerasuolo <cerasuolodomenico@gmail.com>
Signed-off-by: default avatarNhat Pham <nphamcs@gmail.com>
Tested-by: default avatarBagas Sanjaya <bagasdotme@gmail.com>
Acked-by: Chris Li <chrisl@kernel.org> (Google)
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7108cc3f

tools/testing/selftests/cgroup/test_zswap.c

+50 −24
Original line number Diff line number Diff line
@@ -50,9 +50,9 @@ static int get_zswap_stored_pages(size_t *value) 
	return read_int("/sys/kernel/debug/zswap/stored_pages", value);

}



static int get_zswap_written_back_pages(size_t *value)

static int get_cg_wb_count(const char *cg)

{

	return read_int("/sys/kernel/debug/zswap/written_back_pages", value);

	return cg_read_key_long(cg, "memory.stat", "zswp_wb");

}



static long get_zswpout(const char *cgroup)
@@ -73,6 +73,24 @@ static int allocate_bytes(const char *cgroup, void *arg) 
	return 0;

}



static char *setup_test_group_1M(const char *root, const char *name)

{

	char *group_name = cg_name(root, name);



	if (!group_name)

		return NULL;

	if (cg_create(group_name))

		goto fail;

	if (cg_write(group_name, "memory.max", "1M")) {

		cg_destroy(group_name);

		goto fail;

	}

	return group_name;

fail:

	free(group_name);

	return NULL;

}



/*

 * Sanity test to check that pages are written into zswap.

 */
@@ -117,43 +135,51 @@ static int test_zswap_usage(const char *root) 


/*

 * When trying to store a memcg page in zswap, if the memcg hits its memory

 * limit in zswap, writeback should not be triggered.

 *

 * This was fixed with commit 0bdf0efa180a("zswap: do not shrink if cgroup may

 * not zswap"). Needs to be revised when a per memcg writeback mechanism is

 * implemented.

 * limit in zswap, writeback should affect only the zswapped pages of that

 * memcg.

 */

static int test_no_invasive_cgroup_shrink(const char *root)

{

	size_t written_back_before, written_back_after;

	int ret = KSFT_FAIL;

	char *test_group;

	size_t control_allocation_size = MB(10);

	char *control_allocation, *wb_group = NULL, *control_group = NULL;



	/* Set up */

	test_group = cg_name(root, "no_shrink_test");

	if (!test_group)

		goto out;

	if (cg_create(test_group))

	wb_group = setup_test_group_1M(root, "per_memcg_wb_test1");

	if (!wb_group)

		return KSFT_FAIL;

	if (cg_write(wb_group, "memory.zswap.max", "10K"))

		goto out;

	if (cg_write(test_group, "memory.max", "1M"))

	control_group = setup_test_group_1M(root, "per_memcg_wb_test2");

	if (!control_group)

		goto out;

	if (cg_write(test_group, "memory.zswap.max", "10K"))



	/* Push some test_group2 memory into zswap */

	if (cg_enter_current(control_group))

		goto out;

	if (get_zswap_written_back_pages(&written_back_before))

	control_allocation = malloc(control_allocation_size);

	for (int i = 0; i < control_allocation_size; i += 4095)

		control_allocation[i] = 'a';

	if (cg_read_key_long(control_group, "memory.stat", "zswapped") < 1)

		goto out;



	/* Allocate 10x memory.max to push memory into zswap */

	if (cg_run(test_group, allocate_bytes, (void *)MB(10)))

	/* Allocate 10x memory.max to push wb_group memory into zswap and trigger wb */

	if (cg_run(wb_group, allocate_bytes, (void *)MB(10)))

		goto out;



	/* Verify that no writeback happened because of the memcg allocation */

	if (get_zswap_written_back_pages(&written_back_after))

		goto out;

	if (written_back_after == written_back_before)

	/* Verify that only zswapped memory from gwb_group has been written back */

	if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(control_group) == 0)

		ret = KSFT_PASS;

out:

	cg_destroy(test_group);

	free(test_group);

	cg_enter_current(root);

	if (control_group) {

		cg_destroy(control_group);

		free(control_group);

	}

	cg_destroy(wb_group);

	free(wb_group);

	if (control_allocation)

		free(control_allocation);

	return ret;

}