diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index e859fecd310b..49def87a909b 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -50,6 +50,66 @@ 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) +{ + return read_int("/sys/kernel/debug/zswap/written_back_pages", value); +} + +static int allocate_bytes(const char *cgroup, void *arg) +{ + size_t size = (size_t)arg; + char *mem = (char *)malloc(size); + + if (!mem) + return -1; + for (int i = 0; i < size; i += 4095) + mem[i] = 'a'; + free(mem); + return 0; +} + +/* + * 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. + */ +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; + + /* Set up */ + test_group = cg_name(root, "no_shrink_test"); + if (!test_group) + goto out; + if (cg_create(test_group)) + goto out; + if (cg_write(test_group, "memory.max", "1M")) + goto out; + if (cg_write(test_group, "memory.zswap.max", "10K")) + goto out; + if (get_zswap_written_back_pages(&written_back_before)) + goto out; + + /* Allocate 10x memory.max to push memory into zswap */ + if (cg_run(test_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) + ret = KSFT_PASS; +out: + cg_destroy(test_group); + free(test_group); + return ret; +} + struct no_kmem_bypass_child_args { size_t target_alloc_bytes; size_t child_allocated; @@ -176,6 +236,7 @@ struct zswap_test { const char *name; } tests[] = { T(test_no_kmem_bypass), + T(test_no_invasive_cgroup_shrink), }; #undef T