From mboxrd@z Thu Jan 1 00:00:00 1970 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 B9E3C18C35B for ; Mon, 15 Jul 2024 14:00:29 +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=1721052031; cv=none; b=tiSxSaOkG0he7HkNH2qsZgY0Ynx1LHFHLoZXu2sxFdigYDPZ/X3Y5p1VQNskgdZIqKDLFvrlIrEs6aNKkSLFqII8VYFbX7Nzkd8Wif6+rdRbpoXPYFA0G5x6D6xnxfVJcJmtIxh01UF/SktTj64EII2ggT6L+eV2UQxOUzakhcg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721052031; c=relaxed/simple; bh=RgfB9i51/BJ2f/wvWX+DMEe+gK+qdqWx8xFVzEBeYjQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=N4RIjTaQqLC/yEgngr3iE/9f+l0XThvRuC8EX8rsuzzhcw89GP3ScCJUowRXEBDn/pfQA22JFKCzWJJXyOhoJbHsr0xGn2+iuw+FNZJKNlCc6J1ZCZrfJYwF7d4AOB7ctUC3h48HsbxU+KnZz/2EDzsaxYgpJTofuDhaosIwoYY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=QICMrA05; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="QICMrA05" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721052027; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GVYJ4ne2AQmg1BRrD/nHV6rBCTnsNSLJ9SYDD3aJK7U=; b=QICMrA05TpCZe6gvwiCOj2GZnAkpeG0JTtIyx2hOyAKJ1uN4HZ4w/aSEmzPkxVdFjgbm1u 2qFxRYQP1LZxhFdYgYLW9V73jsK/gdmrhgtry75mWgboHehXgz3zOet+Tz1clZsvkLeMAR RTQtvZ6Coh6NfPvWZXO/xYOiBvvKeb8= Received: from mx-prod-mc-04.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-3-mbyqor8aNMOa0P2D-TnHjQ-1; Mon, 15 Jul 2024 10:00:23 -0400 X-MC-Unique: mbyqor8aNMOa0P2D-TnHjQ-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 75D031955D4C; Mon, 15 Jul 2024 14:00:20 +0000 (UTC) Received: from [10.22.9.29] (unknown [10.22.9.29]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 078DA1955D42; Mon, 15 Jul 2024 14:00:17 +0000 (UTC) Message-ID: <3061f280-5a4a-4ff6-8b90-ab667a7e8e48@redhat.com> Date: Mon, 15 Jul 2024 10:00:17 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH-patch v6] cgroup: Show # of subsystem CSSes in cgroup.stat To: Kamalesh Babulal , Tejun Heo , Zefan Li , Johannes Weiner , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Jonathan Corbet Cc: cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Roman Gushchin References: <20240712232959.2494935-1-longman@redhat.com> <8481d9d6-04dd-4c33-ad38-fc8ca1667d16@oracle.com> Content-Language: en-US From: Waiman Long In-Reply-To: <8481d9d6-04dd-4c33-ad38-fc8ca1667d16@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On 7/13/24 11:50, Kamalesh Babulal wrote: > On 7/13/24 4:59 AM, Waiman Long wrote: >> Cgroup subsystem state (CSS) is an abstraction in the cgroup layer to >> help manage different structures in various cgroup subsystems by being >> an embedded element inside a larger structure like cpuset or mem_cgroup. >> >> The /proc/cgroups file shows the number of cgroups for each of the >> subsystems. With cgroup v1, the number of CSSes is the same as the >> number of cgroups. That is not the case anymore with cgroup v2. The >> /proc/cgroups file cannot show the actual number of CSSes for the >> subsystems that are bound to cgroup v2. >> >> So if a v2 cgroup subsystem is leaking cgroups (usually memory cgroup), >> we can't tell by looking at /proc/cgroups which cgroup subsystems may >> be responsible. >> >> As cgroup v2 had deprecated the use of /proc/cgroups, the hierarchical >> cgroup.stat file is now being extended to show the number of live and >> dying CSSes associated with all the non-inhibited cgroup subsystems >> that have been bound to cgroup v2 as long as they are not both zero. >> The number includes CSSes in the current cgroup as well as in all the >> descendants underneath it. This will help us pinpoint which subsystems >> are responsible for the increasing number of dying (nr_dying_descendants) >> cgroups. >> >> The CSSes dying counts are stored in the cgroup structure itself >> instead of inside the CSS as suggested by Johannes. This will allow >> us to accurately track dying counts of cgroup subsystems that have >> recently been disabled in a cgroup. It is now possible that a zero >> subsystem number is coupled with a non-zero dying subsystem number. >> >> The cgroup-v2.rst file is updated to discuss this new behavior. >> >> With this patch applied, a sample output from root cgroup.stat file >> was shown below. >> >> nr_descendants 56 >> nr_subsys_cpuset 1 >> nr_subsys_cpu 43 >> nr_subsys_io 43 >> nr_subsys_memory 56 >> nr_subsys_perf_event 57 >> nr_subsys_hugetlb 1 >> nr_subsys_pids 56 >> nr_subsys_rdma 1 >> nr_subsys_misc 1 >> nr_dying_descendants 30 >> nr_dying_subsys_cpuset 0 >> nr_dying_subsys_cpu 0 >> nr_dying_subsys_io 0 >> nr_dying_subsys_memory 30 >> nr_dying_subsys_perf_event 0 >> nr_dying_subsys_hugetlb 0 >> nr_dying_subsys_pids 0 >> nr_dying_subsys_rdma 0 >> nr_dying_subsys_misc 0 >> >> Another sample output from system.slice/cgroup.stat was: >> >> nr_descendants 32 >> nr_subsys_cpu 30 >> nr_subsys_io 30 >> nr_subsys_memory 32 >> nr_subsys_perf_event 33 >> nr_subsys_pids 32 >> nr_dying_descendants 32 >> nr_dying_subsys_cpu 0 >> nr_dying_subsys_io 0 >> nr_dying_subsys_memory 32 >> nr_dying_subsys_perf_event 0 >> nr_dying_subsys_pids 0 >> > [...] > >> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c >> index c8e4b62b436a..73774c841100 100644 >> --- a/kernel/cgroup/cgroup.c >> +++ b/kernel/cgroup/cgroup.c >> @@ -3669,12 +3669,43 @@ static int cgroup_events_show(struct seq_file *seq, void *v) >> static int cgroup_stat_show(struct seq_file *seq, void *v) >> { >> struct cgroup *cgroup = seq_css(seq)->cgroup; >> + struct cgroup_subsys_state *css; >> + int dying_cnt[CGROUP_SUBSYS_COUNT]; >> + int ssid; >> >> seq_printf(seq, "nr_descendants %d\n", >> cgroup->nr_descendants); >> + >> + /* >> + * Show the number of live and dying csses associated with each of >> + * non-inhibited cgroup subsystems that is either enabled in current >> + * cgroup or has non-zero dying count. >> + * >> + * Without proper lock protection, racing is possible. So the >> + * numbers may not be consistent when that happens. >> + */ >> + rcu_read_lock(); >> + for (ssid = 0; ssid < CGROUP_SUBSYS_COUNT; ssid++) { >> + dying_cnt[ssid] = -1; >> + if (BIT(ssid) & cgrp_dfl_inhibit_ss_mask) >> + continue; >> + css = rcu_dereference_raw(cgroup->subsys[ssid]); >> + if (!css && !cgroup->nr_dying_subsys[ssid]) >> + continue; > Sorry, If I have misread the discussion from the other thread about displaying > nr_descendants and nr_dying_subsys_. I believe the idea was to print > them for enabled and disabled cgroup controllers, so the output stays consistent > and does not vary depending on the enabled controllers or previously enabled > controller with nr_dying_subsys > 0. > > For example, on a rebooted vm: > > # cd /sys/fs/cgroup/ > # cat cgroup.subtree_control > cpu memory pids > > # mkdir foo > # cat foo/cgroup.stat > nr_descendants 0 > nr_subsys_cpu 1 > nr_subsys_memory 1 > nr_subsys_perf_event 1 > nr_subsys_pids 1 > nr_dying_descendants 0 > nr_dying_subsys_cpu 0 > nr_dying_subsys_memory 0 > nr_dying_subsys_perf_event 0 > nr_dying_subsys_pids 0 > > # echo '+cpuset' > cgroup.subtree_control > > # cat foo/cgroup.stat > nr_descendants 0 > nr_subsys_cpuset 1 > nr_subsys_cpu 1 > nr_subsys_memory 1 > nr_subsys_perf_event 1 > nr_subsys_pids 1 > nr_dying_descendants 0 > nr_dying_subsys_cpuset 0 > nr_dying_subsys_cpu 0 > nr_dying_subsys_memory 0 > nr_dying_subsys_perf_event 0 > nr_dying_subsys_pids 0 I am fine with fine with that. I will update the patch as suggested. Thanks, Longman >> + >> + dying_cnt[ssid] = cgroup->nr_dying_subsys[ssid]; >> + seq_printf(seq, "nr_subsys_%s %d\n", cgroup_subsys[ssid]->name, >> + css ? (css->nr_descendants + 1) : 0); >> + } >> + >> seq_printf(seq, "nr_dying_descendants %d\n", >> cgroup->nr_dying_descendants); >> - >> + for (ssid = 0; ssid < CGROUP_SUBSYS_COUNT; ssid++) { >> + if (dying_cnt[ssid] >= 0) >> + seq_printf(seq, "nr_dying_subsys_%s %d\n", >> + cgroup_subsys[ssid]->name, dying_cnt[ssid]); >> + } >> + rcu_read_unlock(); >> return 0; >> } >>