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Thu, 20 Nov 2025 14:04:18 +0800 From: Guopeng Zhang To: tj@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, mkoutny@suse.com, muchun.song@linux.dev Cc: lance.yang@linux.dev, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Guopeng Zhang Subject: [PATCH v3] selftests: cgroup: make test_memcg_sock robust against delayed sock stats Date: Thu, 20 Nov 2025 14:04:06 +0800 Message-Id: <20251120060406.2846257-1-zhangguopeng@kylinos.cn> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: g8a95a5g1ic7h7ickwc1xqkzfcwpu36f X-Rspam-User: X-Rspamd-Queue-Id: 11CE420005 X-Rspamd-Server: rspam10 X-HE-Tag: 1763618665-362948 X-HE-Meta: U2FsdGVkX1/MdJDfgAC0TMQoqt30k8xudlPvidzBhqHHlo/rffmbTpgPCJdOk0qolTK4m6tJD0cwHYUDAqTPWXjKitDo0mqvjBefGPmPcvo0VEaTGkaMFJnd1x9FQpt9rUlM1bgkMs2evw6O37IkBQVog6es7KY8yJtfq68tKXU51LaslEbogPIrjbPTslu8l5Xmd55fifLE7yfx5cpqWmk4LrmzyNHk45lOkfTazhchjEIYYwj6ulDFAx1wJXI3EbW9ebDcRnhLZEgEqmw2DIgLUqgGHF4m00RTyTIQCzaS6OjlyBRXCluoyfbH/GsOeCJgcNOl1wIWn/JweNxdfhV/ucYrmh0Bh71Dig27M8AYbDCAzXm1Buc6Rg6GPdfimZ0D5eMAqqKkRkbdJshUeFeucJIuc52/4ClsXEemKlm8VVrojBYjlp9I7qQlZjGccogWLFQQ4NcdwRF8SVFfcffUCTnBgyez4PzlwFzToy0G2Y3zU/1hDDMBYDHMiNX/Aynhfo/6LGYu9y4tK53NTtZAGSb0n4+xFKQMm0ii+yy/ZBnQdrq7BkOnTqrc4fyDhuoaFa0OskWSCU0Y2ZYMLd6BQwL7cfT9JU2z8uUU6u6bflkBRJVwD3QiV4rh0mSA3uEsH48FdAn2hPRv+fUf4G/Od8HhOUifMRZ0izf0UQ+El0A5/RrEl1D7T9aJ4yEfcnp36ehMHFFR6Jf90xPvR+aNFvORIZTx8mlzlhVDIZmbMqfVQnDPwxXhbue83J8MNJus6PQEtLp0cgA5mK4tHCFZLjQpwchB1pWWo2wSPwzRwevv6Fg/D2ZslSMCF6iYGjUqYBxWtZ9HNnVkS8p/GmvHAV+CcnDmhEpooLO/J7qM2VkqK8Jr+nQJ7Wf58BEfz6l9a/VbMtGA6iTWUceQ4euZQiFpddJzt8F/djOil9XxpHSp8HJT1rigQY1n0TJuOKsP2e5ff25D9pMIm+k fnTcqhOi btgXT++1bzsjdNmsslDP6PHxzqqaQVZ8OwfgsJkJggYqZmBspSZTYb3oNtg== 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: test_memcg_sock() currently requires that memory.stat's "sock " counter is exactly zero immediately after the TCP server exits. On a busy system this assumption is too strict: - Socket memory may be freed with a small delay (e.g. RCU callbacks). - memcg statistics are updated asynchronously via the rstat flushing worker, so the "sock " value in memory.stat can stay non-zero for a short period of time even after all socket memory has been uncharged. As a result, test_memcg_sock() can intermittently fail even though socket memory accounting is working correctly. Make the test more robust by polling memory.stat for the "sock " counter and allowing it some time to drop to zero instead of checking it only once. The timeout is set to 3 seconds to cover the periodic rstat flush interval (FLUSH_TIME = 2*HZ by default) plus some scheduling slack. If the counter does not become zero within the timeout, the test still fails as before. On my test system, running test_memcontrol 50 times produced: - Before this patch: 6/50 runs passed. - After this patch: 50/50 runs passed. Suggested-by: Lance Yang Reviewed-by: Lance Yang Signed-off-by: Guopeng Zhang --- v3: - Move MEMCG_SOCKSTAT_WAIT_* defines after the #include block as suggested. v2: - Mention the periodic rstat flush interval (FLUSH_TIME = 2*HZ) in the comment and clarify the rationale for the 3s timeout. - Replace the hard-coded retry count and wait interval with macros to avoid magic numbers and make the 3s timeout calculation explicit. --- .../selftests/cgroup/test_memcontrol.c | 30 ++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index 4e1647568c5b..8ff7286fc80b 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -21,6 +21,9 @@ #include "kselftest.h" #include "cgroup_util.h" +#define MEMCG_SOCKSTAT_WAIT_RETRIES 30 /* 3s total */ +#define MEMCG_SOCKSTAT_WAIT_INTERVAL_US (100 * 1000) /* 100 ms */ + static bool has_localevents; static bool has_recursiveprot; @@ -1384,6 +1387,8 @@ static int test_memcg_sock(const char *root) int bind_retries = 5, ret = KSFT_FAIL, pid, err; unsigned short port; char *memcg; + long sock_post = -1; + int i; memcg = cg_name(root, "memcg_test"); if (!memcg) @@ -1432,7 +1437,30 @@ static int test_memcg_sock(const char *root) if (cg_read_long(memcg, "memory.current") < 0) goto cleanup; - if (cg_read_key_long(memcg, "memory.stat", "sock ")) + /* + * memory.stat is updated asynchronously via the memcg rstat + * flushing worker, which runs periodically (every 2 seconds, + * see FLUSH_TIME). On a busy system, the "sock " counter may + * stay non-zero for a short period of time after the TCP + * connection is closed and all socket memory has been + * uncharged. + * + * Poll memory.stat for up to 3 seconds (~FLUSH_TIME plus some + * scheduling slack) and require that the "sock " counter + * eventually drops to zero. + */ + for (i = 0; i < MEMCG_SOCKSTAT_WAIT_RETRIES; i++) { + sock_post = cg_read_key_long(memcg, "memory.stat", "sock "); + if (sock_post < 0) + goto cleanup; + + if (!sock_post) + break; + + usleep(MEMCG_SOCKSTAT_WAIT_INTERVAL_US); + } + + if (sock_post) goto cleanup; ret = KSFT_PASS; -- 2.25.1