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Mon, 7 Apr 2025 16:23:30 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.90.98]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 806B4180175B; Mon, 7 Apr 2025 16:23:28 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Tejun Heo , =?utf-8?q?Michal_Koutn=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 v5 2/2] selftests: memcg: Increase error tolerance of child memory.current check in test_memcg_protection() Date: Mon, 7 Apr 2025 12:23:16 -0400 Message-ID: <20250407162316.1434714-3-longman@redhat.com> In-Reply-To: <20250407162316.1434714-1-longman@redhat.com> References: <20250407162316.1434714-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Queue-Id: 037ABC000B X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: 9i3hxhxpwrfob18c8qq6oskj4nnx8bag X-HE-Tag: 1744043017-16417 X-HE-Meta: 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 OFgeR4Up sqlS1bRPaJ2kY5mPqZZVEyoSbhlDGTX894dHQhz4PuGN3UKauc0Lh5Yi2iz1AkAv9BNg1zY7JGoLB/YzI7tLShm2YWmNetvIwlALUST972o2JCuhWoF/NTQZFLcaH94Yg/e3T/3AfZiQ3ndoA/+dy0+vKAv+F7uCdhdWH3WIH/g0NK3hVlibr63Zvt07/9YLmSyWTtcjy9edOb/tG7PgcHRfCj22f6XjJ8+1AOoxIAE0aA72TwMl3KB4DtGxDWW6UBkMG5wqpCm7AEZgnKFyNH0pDMDuYaUXf2fqsrp5+cilIh89TwTxVLXT+44odI/i5aJuyr38TGmR0RcpWrKgvx+IWzl1dx7SHl7hBbAUpc9+sbYqzxfkC9DXoG/k3VHHG7ukP 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. 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 bab826b6b7b0..8f4f2479650e 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -495,10 +495,10 @@ 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)