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Mon, 29 Jun 2026 04:21:31 -0700 (PDT) Received: from localhost.localdomain ([210.184.73.204]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c7f63d09f0sm92759085ad.56.2026.06.29.04.21.26 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 29 Jun 2026 04:21:31 -0700 (PDT) From: Hao Jia To: akpm@linux-foundation.org, tj@kernel.org, hannes@cmpxchg.org, shakeel.butt@linux.dev, mhocko@kernel.org, yosry@kernel.org, mkoutny@suse.com, nphamcs@gmail.com, chengming.zhou@linux.dev, muchun.song@linux.dev, roman.gushchin@linux.dev Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Hao Jia Subject: [PATCH v5 6/6] selftests/cgroup: Add tests for zswap proactive writeback Date: Mon, 29 Jun 2026 19:20:32 +0800 Message-Id: <20260629112032.20423-7-jiahao.kernel@gmail.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) In-Reply-To: <20260629112032.20423-1-jiahao.kernel@gmail.com> References: <20260629112032.20423-1-jiahao.kernel@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BD4561A0005 X-Stat-Signature: p6rdd3zeti5xzenn7pic3ffhrodthqy5 X-HE-Tag: 1782732092-212006 X-HE-Meta: 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 A+x6iIva qUmoAdK90tWXXu+f8t9SeHw5YGHlWOXW41Kk/z0K1mWmDMQsqCH4IqOy5rJs1FXpiGVyAZSa08LpaOdsZEOXQl+e8Sb/m9/OjUl2897O7RbnTPZXtdhs6J8edwzs7iW8TZCB5witZRQuG0XQ6NPq0qjo5msifDmomOQNnfzPzUfJVic1Mt9hC84GKKK/8Xy8iPoZi2DnTmGyp9I1IEsJoVRYBp3d5fPJzNIeVa6GVQvq0mo50Gh1/8lVUV9wfFBXYxqXjSZJHgpB9Vzlew6aJceVJoQ/s1L0uoiY7asQECvDjGrNi/vqyCfMplNQv8a9nvaE16gl/5u7YroU7SWVwDxxMJOtaFTwmD2QoC0KpJMHNTfkc92X40+D9M/9vthJ9WubaydS61KXRH9mvcHNocHMA9Wpd8BKuhyuBEeQ2/7ga6VBfJjHduxZOrIW5zUDazeeeRVW5ABL2N3aey4IH92hVnGbrd/+yCSAVyz6ogfCBFic= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Hao Jia Add test_zswap_proactive_writeback() to cover the new memory.reclaim "source=zswap" key. The test populates a memory cgroup zswap pool, triggers proactive writeback, and verifies the behavior by observing the change in zswpwb_proactive_b. Invalid input combinations are also covered. Extend test_zswap_writeback_one() to assert that the existing non-proactive writeback path leaves zswpwb_proactive_b at zero. Signed-off-by: Hao Jia --- tools/testing/selftests/cgroup/test_zswap.c | 161 +++++++++++++++++++- 1 file changed, 160 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/cgroup/test_zswap.c b/tools/testing/selftests/cgroup/test_zswap.c index 49b36ee79160..dfd5f24b9d99 100644 --- a/tools/testing/selftests/cgroup/test_zswap.c +++ b/tools/testing/selftests/cgroup/test_zswap.c @@ -60,7 +60,12 @@ static int get_zswap_stored_pages(size_t *value) static long get_cg_wb_count(const char *cg) { - return cg_read_key_long(cg, "memory.stat", "zswpwb"); + return cg_read_key_long(cg, "memory.stat", "zswpwb "); +} + +static long get_cg_pwb_bytes(const char *cg) +{ + return cg_read_key_long(cg, "memory.stat", "zswpwb_proactive_b "); } static long get_zswpout(const char *cgroup) @@ -355,6 +360,7 @@ static int attempt_writeback(const char *cgroup, void *arg) static int test_zswap_writeback_one(const char *cgroup, bool wb) { long zswpwb_before, zswpwb_after; + long pwb_bytes; zswpwb_before = get_cg_wb_count(cgroup); if (zswpwb_before != 0) { @@ -362,6 +368,12 @@ static int test_zswap_writeback_one(const char *cgroup, bool wb) return -1; } + pwb_bytes = get_cg_pwb_bytes(cgroup); + if (pwb_bytes > 0) { + ksft_print_msg("zswpwb_proactive_b_before = %ld instead of 0\n", pwb_bytes); + return -1; + } + if (cg_run(cgroup, attempt_writeback, (void *) &wb)) return -1; @@ -379,6 +391,17 @@ static int test_zswap_writeback_one(const char *cgroup, bool wb) return -1; } + /* + * attempt_writeback() does not use the proactive writeback path, so + * zswpwb_proactive_b must stay at zero regardless of whether + * writeback was enabled. + */ + pwb_bytes = get_cg_pwb_bytes(cgroup); + if (pwb_bytes > 0) { + ksft_print_msg("zswpwb_proactive_b_after is %ld, expected 0\n", pwb_bytes); + return -1; + } + return 0; } @@ -770,6 +793,141 @@ static int test_zswap_incompressible(const char *root) return ret; } +/* + * Trigger proactive zswap writeback with the following steps: + * 1. Allocate memory. + * 2. Push allocated memory into zswap. + * 3. Proactively write back zswap pages to swap + * using "source=zswap". + */ +static int proactive_writeback_workload(const char *cgroup, void *arg) +{ + long pagesize = sysconf(_SC_PAGESIZE); + size_t memsize = pagesize * 1024; + char reclaim_cmd[64]; + char buf[pagesize]; + long zswap_usage; + int ret = -1; + int rc; + char *mem; + + mem = (char *)malloc(memsize); + if (!mem) + return ret; + + for (int i = 0; i < pagesize; i++) + buf[i] = i < pagesize / 2 ? (char)i : 0; + for (int i = 0; i < memsize; i += pagesize) + memcpy(&mem[i], buf, pagesize); + + /* Evict allocated memory into zswap. */ + if (cg_write_numeric(cgroup, "memory.reclaim", memsize)) { + ksft_print_msg("Failed to push pages into zswap\n"); + goto out; + } + + zswap_usage = cg_read_long(cgroup, "memory.zswap.current"); + if (zswap_usage <= 0) { + ksft_print_msg("no zswap pool to write back\n"); + goto out; + } + + /* Trigger proactive zswap writeback. */ + snprintf(reclaim_cmd, sizeof(reclaim_cmd), "%ld source=zswap", zswap_usage); + rc = cg_write(cgroup, "memory.reclaim", reclaim_cmd); + if (rc && rc != -EAGAIN) { + ksft_print_msg("proactive zswap writeback failed: %d\n", rc); + goto out; + } + + ret = 0; +out: + free(mem); + return ret; +} + +static int check_writeback_invalid_inputs(const char *cgroup) +{ + static char * const bad_inputs[] = { + "source=zswap", + "1M source=zswap swappiness=60", + "1M swappiness=60 source=zswap", + "1M source=zswap swappiness=max", + "1M swappiness=max source=zswap", + }; + int i, rc; + + for (i = 0; i < ARRAY_SIZE(bad_inputs); i++) { + rc = cg_write(cgroup, "memory.reclaim", bad_inputs[i]); + if (rc != -EINVAL) { + ksft_print_msg("memory.reclaim '%s': returned %d, expected %d\n", + bad_inputs[i], rc, -EINVAL); + return -1; + } + } + return 0; +} + +static int test_zswap_proactive_writeback(const char *root) +{ + long wb_before, wb_after; + long pwb_b_before, pwb_b_after; + long wb_delta, pwb_b_delta; + int ret = KSFT_FAIL; + char *test_group; + + if (cg_read_strcmp(root, "memory.zswap.writeback", "1")) + return KSFT_SKIP; + + test_group = cg_name(root, "zswap_proactive_test"); + if (!test_group) + return KSFT_FAIL; + if (cg_create(test_group)) + goto out; + /* + * A missing zswpwb_proactive_b stat means the kernel lacks proactive + * writeback support, so skip rather than fail. + */ + if (get_cg_pwb_bytes(test_group) < 0) { + ret = KSFT_SKIP; + goto out; + } + if (check_writeback_invalid_inputs(test_group)) + goto out; + + pwb_b_before = get_cg_pwb_bytes(test_group); + wb_before = get_cg_wb_count(test_group); + if (pwb_b_before < 0 || wb_before < 0) + goto out; + + if (cg_run(test_group, proactive_writeback_workload, NULL)) + goto out; + + pwb_b_after = get_cg_pwb_bytes(test_group); + wb_after = get_cg_wb_count(test_group); + if (pwb_b_after < 0 || wb_after < 0) + goto out; + + pwb_b_delta = pwb_b_after - pwb_b_before; + wb_delta = wb_after - wb_before; + + if (pwb_b_delta <= 0) { + ksft_print_msg("zswpwb_proactive_b did not increase: delta=%ld\n", + pwb_b_delta); + goto out; + } + if (wb_delta <= 0) { + ksft_print_msg("zswpwb did not increase: delta=%ld\n", wb_delta); + goto out; + } + + ret = KSFT_PASS; +out: + cg_destroy(test_group); + free(test_group); + return ret; +} + #define T(x) { x, #x } struct zswap_test { int (*fn)(const char *root); @@ -783,6 +941,7 @@ struct zswap_test { T(test_no_kmem_bypass), T(test_no_invasive_cgroup_shrink), T(test_zswap_incompressible), + T(test_zswap_proactive_writeback), }; #undef T -- 2.34.1