On Mon, Feb 5, 2024 at 3:05 PM Yosry Ahmed yosryahmed@google.com wrote:
On Mon, Feb 05, 2024 at 02:56:08PM -0800, Nhat Pham wrote:
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.
Suggested-by: Rik van Riel riel@surriel.com Suggested-by: Yosry Ahmed yosryahmed@google.com Signed-off-by: Nhat Pham nphamcs@gmail.com
LGTM with a few nits below: Acked-by: Yosry Ahmed yosryahmed@google.com
Thanks!
tools/testing/selftests/cgroup/test_zswap.c | 120 +++++++++++++++++++- 1 file changed, 119 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 32ce975b21d1..c263610a4a60 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -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 */nit: s/go/Go
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 */We removed this comment here.
test_group = cg_name(root, "no_shrink_test"); if (!test_group) goto out;@@ -133,6 +153,102 @@ 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 == 0) {ksft_print_msg("pages should be swapped out\n");goto out;}We can actually check that this number is >= 24M instead. Not a big deal, but might as well.
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;/* Set up */Yet we added a similar one here :)
Urgh I am stupid :) I meant to remove this, but accidentally removed it from the old test instead :)
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 == 0) {ksft_print_msg("zswpin should not be 0\n");goto out;}Same here, we can check that zswpin is at least 24M worth of events. Again, not a big deal, but might as well.