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Fri, 2 May 2025 01:05:00 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.80.189]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 5377719560A3; Fri, 2 May 2025 01:04:57 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Tejun Heo , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Shuah Khan Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Waiman Long Subject: [PATCH v8 2/2] selftests: memcg: Increase error tolerance of child memory.current check in test_memcg_protection() Date: Thu, 1 May 2025 21:04:43 -0400 Message-ID: <20250502010443.106022-3-longman@redhat.com> In-Reply-To: <20250502010443.106022-1-longman@redhat.com> References: <20250502010443.106022-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4528080009 X-Stat-Signature: 8swn1sbsx1uwz6wb8peu6s5ikfs6amnu X-Rspam-User: X-HE-Tag: 1746147908-657030 X-HE-Meta: U2FsdGVkX1+4TwXzYFNMKWKCsQQ6tOnY799crmdBKQVfMeDIB0VYUr7OGQli2aaxl6AU00KIqsiBfaDHWUzVXIvXX1qM/SJ+0hpYHID0mTgRxh29OW9YGvHFNZlpUF6YCN5GqKSc7VO1/Tjetn1Rb7RGX10uTmaFyJI4QuLqCcFVNqUmg9KUiZ2NK5ipEqH8zac0uLaiKOg2amZONZF5Yag37ZRvVQ4t8Uh/oLsJ+/n0FNRXZBf7YwaQyILVggHR4C9zQ88dAqKHr8MI/H7Ist6ag/vUf4kIUKYrA8NQiRAZtoapMkuCxTUOg3HP4yNbBUabiBfrGGVLi7KPJjBY6SXPOBcWnVlnPrRddKnSSCojYCEFQvwpfTJh1xi/2oc/b3U0pOdYnFTxdwkEM9wlxnpNZKkE3u7dhwA7CmRlKnmr0+cdwvGlPHWEt6/rYTgCl+UQ+0Qfg6TNstiP3pEdfhHz6M3GUAxzpfHyu+qPvRULQ83jUUlMBzIBkJAZGQFI9yYHlB1EkS9jLHlW8lnE6g3AKbAWEGcnkFZeghVVwjP13ac1Q1FpcKHKqO5DMOgi21YU1KNguDkc8lJ3blIjHyY++A45Vr9UMxTavNY80dAQYmDXt9r91lRW0K144UqVFG/C1mUunoScCgp8Q+HxmacWGv/vfK7aHUK5H3hzHaiH2Q+fgLu7OI+YBBIhi5Si85uEZ1MUjHSEP7m3wogHYXv3Svw4b5MMEclkw2IfzTNBQ7FzPNujVNTOX7zUbzKDuGNM5t9qIcFS4boevVU8ucILNaxVctDT/O5Z9ILXh5q/++vwYne1axBm3xte9UPaq3I2AtvTkrMSD1BHtRDeiyvJB2bBy/MYvdLY+iJXYK8Ey1vyxa8k53Cr78vxr3p6vEmG3QNB3qsClZLRoiog+5UfF0GSfXBgrbREL9Q5Y25GvMv5RhiYO2atYTf1/FRo4Zb9EkP60QpO8zRBsNx Ea7x7iXR ZBi1m9n9TsJHXwit5f3jujOVDUoLjgJkdFjkki3HRaKPN9pmJrqi+QTYrReHlTRPAoE17twbIRREEghBYvTHI/l79hZmYQT2KVFwTLpWewye1GgOa11zTS7xeRC8GckNg6dpYrJaHS3BcDfXQ6eyFj20K9Z6JtcRmFmXXKOxylVnArUF52v13W0390tYDFMXMx03uv0AoidentAhm7/B9uzNs4mVHNdR/8E80o8psWQlDuuVBMKb4TycyS+1iV48AIwmh5tI3omw2StmNr7MI10MR7qt9a3TM+ddzzwpR7xDebvQtjuONIWJgjOpTtNIa8NwuOlcFB3RkhWwWbCHmy2qvitp8V6cgvRC1rR6G9eT1/ywga38iAZGBsBNvY9Sh1t6w 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: The test_memcg_protection() function is used for the test_memcg_min and test_memcg_low sub-tests. This function generates a set of parent/child cgroups like: parent: memory.min/low = 50M child 0: memory.min/low = 75M, memory.current = 50M child 1: memory.min/low = 25M, memory.current = 50M child 2: memory.min/low = 0, memory.current = 50M After applying memory pressure, the function expects the following actual memory usages. parent: memory.current ~= 50M child 0: memory.current ~= 29M child 1: memory.current ~= 21M child 2: memory.current ~= 0 In reality, the actual memory usages can differ quite a bit from the expected values. It uses an error tolerance of 10% with the values_close() helper. Both the test_memcg_min and test_memcg_low sub-tests can fail sporadically because the actual memory usage exceeds the 10% error tolerance. Below are a sample of the usage data of the tests runs that fail. Child Actual usage Expected usage %err ----- ------------ -------------- ---- 1 16990208 22020096 -12.9% 1 17252352 22020096 -12.1% 0 37699584 30408704 +10.7% 1 14368768 22020096 -21.0% 1 16871424 22020096 -13.2% The current 10% error tolerenace might be right at the time test_memcontrol.c was first introduced in v4.18 kernel, but memory reclaim have certainly evolved quite a bit since then which may result in a bit more run-to-run variation than previously expected. Increase the error tolerance to 15% for child 0 and 20% for child 1 to minimize the chance of this type of failure. The tolerance is bigger for child 1 because an upswing in child 0 corresponds to a smaller %err than a similar downswing in child 1 due to the way %err is used in values_close(). Before this patch, a 100 test runs of test_memcontrol produced the following results: 17 not ok 1 test_memcg_min 22 not ok 2 test_memcg_low After applying this patch, there were no test failure for test_memcg_min and test_memcg_low in 100 test runs. However, these tests may still fail once in a while if the memory usage goes beyond the newly extended range. Signed-off-by: Waiman Long --- tools/testing/selftests/cgroup/test_memcontrol.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index 58602c1831f1..d6534d7301a2 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -496,10 +496,10 @@ static int test_memcg_protection(const char *root, bool min) for (i = 0; i < ARRAY_SIZE(children); i++) c[i] = cg_read_long(children[i], "memory.current"); - if (!values_close(c[0], MB(29), 10)) + if (!values_close(c[0], MB(29), 15)) goto cleanup; - if (!values_close(c[1], MB(21), 10)) + if (!values_close(c[1], MB(21), 20)) goto cleanup; if (c[3] != 0) -- 2.49.0