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Sun, 6 Apr 2025 02:40:27 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.64.19]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id DDA331801766; Sun, 6 Apr 2025 02:40:24 +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 v3 1/2] mm/vmscan: Skip memcg with !usage in shrink_node_memcgs() Date: Sat, 5 Apr 2025 22:40:09 -0400 Message-ID: <20250406024010.1177927-2-longman@redhat.com> In-Reply-To: <20250406024010.1177927-1-longman@redhat.com> References: <20250406024010.1177927-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Queue-Id: 351D040002 X-Rspamd-Server: rspam05 X-Rspam-User: X-Stat-Signature: k5eqm14hzsbaq5ry75isg77yswoubm5i X-HE-Tag: 1743907234-786184 X-HE-Meta: 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 JrK1YVND nyQCM4PBve14ooGRoXTKpRcjdO/4qGMK/MKDMDNBrIYL3oPKS9uZW33+flXENrm0/1EdJ2Mkm5d+2rKqVE77k42ky61wexQKGBdaQsApLKEYcrdRMLT0yjSGb9lI+2w9dn/we5f3T53ROqua5cr1UrG8gj0aKtuGIsoUSqv5irxSTfSZI4nt8lJjepUmTtyhibXQD1SMiG2zvclu+dK0d3G4IaNUtFfq/dmF9H9uCZkT8sScnL5lq9qGCa9PEaYpnwfdUz16Bbn2ObuXFJoGjlvDKQPh7mHn5T5MWgEtW1BwdGv8IIGWpGAiePQ9pxvHrIbKMJXsrIk9mD+sfI5oEOir85G8ZO567lqlogFvLzYsfAlXveAFihJjTrqj27IzCotOy7xFH28YcH4/K2HcEw58dPsneg3FXHJUSfQ0xPyPz5YOqM6R9hCh6YYHwgDiTdLiMDNurHCZfwntzNOwqe0vguibCyvAJyR4a 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_memcontrol selftest consistently fails its test_memcg_low sub-test due to the fact that two of its test child cgroups which have a memmory.low of 0 or an effective memory.low of 0 still have low events generated for them since mem_cgroup_below_low() use the ">=" operator when comparing to elow. The two failed use cases are as follows: 1) memory.low is set to 0, but low events can still be triggered and so the cgroup may have a non-zero low event count. I doubt users are looking for that as they didn't set memory.low at all. 2) memory.low is set to a non-zero value but the cgroup has no task in it so that it has an effective low value of 0. Again it may have a non-zero low event count if memory reclaim happens. This is probably not a result expected by the users and it is really doubtful that users will check an empty cgroup with no task in it and expecting some non-zero event counts. In the first case, even though memory.low isn't set, it may still have some low protection if memory.low is set in the parent. So low event may still be recorded. The test_memcontrol.c test has to be modified to account for that. For the second case, it really doesn't make sense to have non-zero low event if the cgroup has 0 usage. So we need to skip this corner case in shrink_node_memcgs(). With this patch applied, the test_memcg_low sub-test finishes successfully without failure in most cases. Though both test_memcg_low and test_memcg_min sub-tests may still fail occasionally if the memory.current values fall outside of the expected ranges. Suggested-by: Johannes Weiner Signed-off-by: Waiman Long --- mm/vmscan.c | 4 ++++ tools/testing/selftests/cgroup/test_memcontrol.c | 7 ++++++- 2 files changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index b620d74b0f66..2a2957b9dc99 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5963,6 +5963,10 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) mem_cgroup_calculate_protection(target_memcg, memcg); + /* Skip memcg with no usage */ + if (!page_counter_read(&memcg->memory)) + continue; + if (mem_cgroup_below_min(target_memcg, memcg)) { /* * Hard protection. diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index 16f5d74ae762..bab826b6b7b0 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -525,8 +525,13 @@ static int test_memcg_protection(const char *root, bool min) goto cleanup; } + /* + * Child 2 has memory.low=0, but some low protection is still being + * distributed down from its parent with memory.low=50M. So the low + * event count will be non-zero. + */ for (i = 0; i < ARRAY_SIZE(children); i++) { - int no_low_events_index = 1; + int no_low_events_index = 2; long low, oom; oom = cg_read_key_long(children[i], "memory.events", "oom "); From patchwork Sun Apr 6 02:40:10 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 14039284 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02D81C369A1 for ; Sun, 6 Apr 2025 02:40:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 24F366B0008; Sat, 5 Apr 2025 22:40:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D3046B000C; Sat, 5 Apr 2025 22:40:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 06FED6B000A; 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Sun, 6 Apr 2025 02:40:30 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.64.19]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id DA38A1801A6D; Sun, 6 Apr 2025 02:40:27 +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 v3 2/2] selftests: memcg: Increase error tolerance of child memory.current check in test_memcg_protection() Date: Sat, 5 Apr 2025 22:40:10 -0400 Message-ID: <20250406024010.1177927-3-longman@redhat.com> In-Reply-To: <20250406024010.1177927-1-longman@redhat.com> References: <20250406024010.1177927-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: A7340180005 X-Stat-Signature: bj9dgf7ynaqyn86nsaw94iw5j5qfxnan X-Rspam-User: X-HE-Tag: 1743907236-825307 X-HE-Meta: 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 ZAevGL5F Z1YyNRG28ou141HWetlo/1v9esij11RuAiLNS0qNJ36NgX3N6/trSvfCeGlUTwtK8bgdT59rGqzggCGn9vAgZhD/crPh4B/ZYNOtJWoS9j4eoW4QkgNelEwriJKXl6D+VoAY+MIboQ+Uc0IceI6Zd6FFCNgUAabfnfq5kekj2QdHJAmcc/CYMk/3A6M5ip3jb2bKZE3mUqbzo1Vu32+hQfacroSKU4q/mBk92X1M1CphaGCZZ7wz17dFIbNeXYyejuXFK5hxngXQwqQcCtI6s4hFSLEG6QgtFjPHeSTlnonMCk0gIcUqITFjKjO+mTSLBEv6x171zSVeT12Gr9I8k5U1pQvZrx2W68AjE2jEUlcdfIortkrjbztGjuld7d1mcVYYx 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)