From patchwork Fri Apr 4 01:24:34 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 14037962 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D9643433A8 for ; Fri, 4 Apr 2025 01:25:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743729909; cv=none; b=mTgtYQYqixrX5IVi9uO+gDolEc6CTSolJfp4aNdP3az9yvDzWWbEdeXR8FPksCVMO3xeCTa5evgtg4PjQD3XwzXmhCgEzCxJSQGJahrW5wir3smfTEq1s7Bstj8OwrSz4fA3aSBaprUu/siCz7BjRWY7SRMyGXI4sf1wCyptN18= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743729909; c=relaxed/simple; bh=LpA9FyU6S3VEfDl9/LNHrnpW1DCPvRJq3D3FwBIgIGY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Oqp5OftGMJmy9PZbFJK2Oceunyz2Nl21CRrXGXKNf5lLQHkmHWriaB98+CSG4Pmw1lvxhwI6BDZu0fat+LCh3R1Yz8fc+BNJTF4REc2VQrhe8jlwAn2Od8Yu1BLviC5WrdRYZy9OWcOfcNVW0sOmGmdNmt+tLBRmzLTXYLPce0E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=NjVHg9ZX; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NjVHg9ZX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1743729906; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=eeDF4dFIWOS0DFmcqcZYB3wJsohtT8Hr0IIadggs/8c=; b=NjVHg9ZXQTMi8LxUoRcgtbJQWMRdeDKZdf1VXuvHiH1WSTS6oD73QpVLLwX2G88hx6FvdY ndL/dr6SrulxjH1OdTOFdSYhVDvqrgaJchYV8GkgvdwN7Rj6AudDih2AdIE1csDI53Kggr SJFM3HYNteUQeS2tezdJ4V97RoVVXNk= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-360-qnvY40IQO2C4Esh2un-iuA-1; Thu, 03 Apr 2025 21:25:00 -0400 X-MC-Unique: qnvY40IQO2C4Esh2un-iuA-1 X-Mimecast-MFC-AGG-ID: qnvY40IQO2C4Esh2un-iuA_1743729898 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BCD5C1956089; Fri, 4 Apr 2025 01:24:57 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.89.4]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 5B1B3180B489; Fri, 4 Apr 2025 01:24:54 +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 v2 1/2] memcg: Don't generate low/min events if either low/min or elow/emin is 0 Date: Thu, 3 Apr 2025 21:24:34 -0400 Message-ID: <20250404012435.656045-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 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. The simple and naive fix of changing the operator to ">", however, changes the memory reclaim behavior which can lead to other failures as low events are needed to facilitate memory reclaim. So we can't do that without some relatively riskier changes in memory reclaim. Another simpler alternative is to avoid reporting below_low failure if either memory.low or its effective equivalent is 0 which is done by this patch specifically for the two failed use cases above. 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. To be consistent, similar change is appled to mem_cgroup_below_min() as to avoid the two failed use cases above with low replaced by min. Signed-off-by: Waiman Long --- include/linux/memcontrol.h | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 53364526d877..4d4a1f159eaa 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -601,21 +601,31 @@ static inline bool mem_cgroup_unprotected(struct mem_cgroup *target, static inline bool mem_cgroup_below_low(struct mem_cgroup *target, struct mem_cgroup *memcg) { + unsigned long elow; + if (mem_cgroup_unprotected(target, memcg)) return false; - return READ_ONCE(memcg->memory.elow) >= - page_counter_read(&memcg->memory); + elow = READ_ONCE(memcg->memory.elow); + if (!elow || !READ_ONCE(memcg->memory.low)) + return false; + + return page_counter_read(&memcg->memory) <= elow; } static inline bool mem_cgroup_below_min(struct mem_cgroup *target, struct mem_cgroup *memcg) { + unsigned long emin; + if (mem_cgroup_unprotected(target, memcg)) return false; - return READ_ONCE(memcg->memory.emin) >= - page_counter_read(&memcg->memory); + emin = READ_ONCE(memcg->memory.emin); + if (!emin || !READ_ONCE(memcg->memory.min)) + return false; + + return page_counter_read(&memcg->memory) <= emin; } int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp); From patchwork Fri Apr 4 01:24:35 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 14037963 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B79D04438B for ; Fri, 4 Apr 2025 01:25:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743729910; cv=none; b=UnJ8ueIej3WMQaOu/5eLrSU8y93QllRApah6bAXvf9bkscRLgGTtyQTjlunZgW0YD9LZU2LF/vuuFqyyx9gFkaq5vu3iGNaPkXHM3vRlfCX4RzskBjylNXNtuAgDzGOU8T3741ZxZVc4A+4QMd0WAly81aawluhWAkkwBxGU2m8= ARC-Message-Signature: i=1; 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Fri, 4 Apr 2025 01:25:01 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.89.4]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1FAE51828A9F; Fri, 4 Apr 2025 01:24:57 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Tejun Heo , =?utf-8?q?Michal_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 v2 2/2] selftests: memcg: Increase error tolerance of child memory.current check in test_memcg_protection() Date: Thu, 3 Apr 2025 21:24:35 -0400 Message-ID: <20250404012435.656045-2-longman@redhat.com> In-Reply-To: <20250404012435.656045-1-longman@redhat.com> References: <20250404012435.656045-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 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: 19 not ok 3 test_memcg_min 13 not ok 4 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 16f5d74ae762..f442c0c3f5a7 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)