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Wed, 03 Dec 2025 19:57:29 +0800 From: Guopeng Zhang To: tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, shuah@kernel.org, roman.gushchin@linux.dev, lance.yang@linux.dev, shakeel.butt@linux.dev Cc: muchun.song@linux.dev, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Guopeng Zhang Subject: [PATCH v5 3/3] selftests: cgroup: Replace sleep with cg_read_key_long_poll() for waiting on nr_dying_descendants Date: Wed, 3 Dec 2025 19:56:31 +0800 Message-Id: <20251203115631.947908-4-zhangguopeng@kylinos.cn> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20251203115631.947908-1-zhangguopeng@kylinos.cn> References: <20251203115631.947908-1-zhangguopeng@kylinos.cn> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 8E85DC0002 X-Stat-Signature: ytssce8665jfci45t59zi1sg7t9rzquj X-Rspam-User: X-HE-Tag: 1764763063-75688 X-HE-Meta: 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 iTI1NWYN pAh58c1tSdTgCtmwcVVuIqPuuGc6qDn7p2a0r8OvjFBlCAwrWi5KrszhYxA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Replace the manual sleep-and-retry logic in test_kmem_dead_cgroups() with the new helper `cg_read_key_long_poll()`. This change improves the robustness of the test by polling the "nr_dying_descendants" counter in `cgroup.stat` until it reaches 0 or the timeout is exceeded. Additionally, increase the retry timeout to 8 seconds (from 5 seconds) based on testing results: - With 5-second timeout: 4/20 runs passed. - With 8-second timeout: 20/20 runs passed. The 8 second timeout is based on stress testing of test_kmem_dead_cgroups() under load: 5 seconds was occasionally not enough for reclaim of dying descendants to complete, whereas 8 seconds consistently covered the observed latencies. This value is intended as a generous upper bound for the asynchronous reclaim and is not tied to any specific kernel constant, so it can be adjusted in the future if reclaim behavior changes. Signed-off-by: Guopeng Zhang Reviewed-by: Shakeel Butt --- tools/testing/selftests/cgroup/test_kmem.c | 33 ++++++++++------------ 1 file changed, 15 insertions(+), 18 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_kmem.c b/tools/testing/selftests/cgroup/test_kmem.c index ca38525484e3..eeabd34bf083 100644 --- a/tools/testing/selftests/cgroup/test_kmem.c +++ b/tools/testing/selftests/cgroup/test_kmem.c @@ -26,6 +26,7 @@ */ #define MAX_VMSTAT_ERROR (4096 * 64 * get_nprocs()) +#define KMEM_DEAD_WAIT_RETRIES 80 static int alloc_dcache(const char *cgroup, void *arg) { @@ -306,9 +307,7 @@ static int test_kmem_dead_cgroups(const char *root) { int ret = KSFT_FAIL; char *parent; - long dead; - int i; - int max_time = 20; + long dead = -1; parent = cg_name(root, "kmem_dead_cgroups_test"); if (!parent) @@ -323,21 +322,19 @@ static int test_kmem_dead_cgroups(const char *root) if (cg_run_in_subcgroups(parent, alloc_dcache, (void *)100, 30)) goto cleanup; - for (i = 0; i < max_time; i++) { - dead = cg_read_key_long(parent, "cgroup.stat", - "nr_dying_descendants "); - if (dead == 0) { - ret = KSFT_PASS; - break; - } - /* - * Reclaiming cgroups might take some time, - * let's wait a bit and repeat. - */ - sleep(1); - if (i > 5) - printf("Waiting time longer than 5s; wait: %ds (dead: %ld)\n", i, dead); - } + /* + * Allow up to ~8s for reclaim of dying descendants to complete. + * This is a generous upper bound derived from stress testing, not + * from a specific kernel constant, and can be adjusted if reclaim + * behavior changes in the future. + */ + dead = cg_read_key_long_poll(parent, "cgroup.stat", + "nr_dying_descendants ", 0, KMEM_DEAD_WAIT_RETRIES, + DEFAULT_WAIT_INTERVAL_US); + if (dead) + goto cleanup; + + ret = KSFT_PASS; cleanup: cg_destroy(parent); -- 2.25.1