From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5D3E216D4FF for ; Tue, 28 May 2024 16:37:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716914258; cv=none; b=TBWy7NkAX4PiKqmau/p2JhsltAeu0O+yk7rP2JVz+WRku7k8r6pSVYqxd5Ga8qNcNRIppLfuGQdXAFok0RrNCPxX6ix+IExrOt8jVnMpj9c6ZCakOUdMyorkMf3NGAJc3bm33gTNQ1vcZHTJ0yByDPdWHyi8w4DH83qPpbaCFrI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716914258; c=relaxed/simple; bh=/r/SLL08HjdI46x3LF0p3F/u9Isqs916m5IdhjUo0RM=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=bsf4vknn7Ad7r9zaEKyWHx9SyAtWOxfC42de8PHmWfwhthaaf1CvcE0XxoEvFUDvsOxR+AoANUowV9uEBdEAhunREO1usV9rXNhtHMdEvaBh4QYz8tDRxiWMIq04TaaHGxkdQ7hhkdPs8GYT5JlYiZIcn/EGLj/trLuC0r/BFNk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--tjmercier.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=H/1j5USv; arc=none smtp.client-ip=209.85.219.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--tjmercier.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="H/1j5USv" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-df771b4eacbso1760839276.2 for ; Tue, 28 May 2024 09:37:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1716914254; x=1717519054; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=6GEC5jqmiiBW2QPmiEul4IbzhqqHXLiTP01MQ0qoF6U=; b=H/1j5USvXTvJmWhwuOmLQmLvHdkM1QA1Yt5EkrBom21ZMXsaobXqIvximIHr4pIvzY AFpA9EjUNSeJeRveYgHTrvsz1MAkhGVR7bGra7fVK5OfpjPYNQ4Tl7Ol1Bs07WxqFp5x 3bOseOJaSUmMSr1HHAJdHkhr5j5Ml2kCDwDOO3K3PES15sZjSGQ8V4qkd205rgw0BkKG HUfx5HrrQNkRa5RF6aCii//d2Se+BublsMptqKOqKKnWAZy5ciXvmNvzr1zAgy6Fk1N2 wl71h1PIRqXQSNzFS79DwWA/b2SYk2FlcX/ZJjMBVWUWlYnlLzsiaSnHOpIex6zMYAvI pMXA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1716914254; x=1717519054; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=6GEC5jqmiiBW2QPmiEul4IbzhqqHXLiTP01MQ0qoF6U=; b=d/jHUNrA4JoJwvrpcqbzN+ivO9y/6Ndmtye9cZAWeAhSlYKQI6Es65DFWZQnlLToXX CJYzPaaSgPB5qIjGUFO+6TFaGIhd+5q1+ZUvVP142/d1iEmH+YqyGiM/xrIVYv99/TiZ mgIUwDAhc0KMqkse4+WEQgAkNhiCG8+V09O3oMOgZ3MXGqJiJSvZjfaXWSkxlj8ZPEyd 1JGdBgg4UTfQ7Kdhhtm6AflDT/LZVIfGjvTSGsXW1No6twQAG0wGkJC8/4So1YKlvIK6 AgPVOE1Sn+ZgKmW5Z1kfTLJ673SIjDvIgXBcrN+fEYNlAroo2Yagvtr9/AsbUfq6SkNj 0/8Q== X-Forwarded-Encrypted: i=1; AJvYcCVqdY2AppMKR9iIpUavModeA22UtdK7xGg8Q3P8951laEpb83Jz+RPnjqbeWTsW4G5lhWrEzmWzJXE7eJv1vHtASl3cWJyS4r3StFnE X-Gm-Message-State: AOJu0YzuVI0aUvtHZfXD6aCbbVHqc/xet7OwSZqNMm5hV9F8vAwzXEHx 4AN7NYmR2u3gp3MyXIz3PE5+lQDmkDI8JRH6+vcCpXN2EZCiTJIAdi8jjUS0HLuQYOvD8PAC5/4 Pu2N7oNL/igojvA== X-Google-Smtp-Source: AGHT+IFCM8agQwohlgmz/X20yI5XC7cbVbMVjBbNM657wC++i+TlAhU6zWE3+cMrzjDCjID8rBD8gKeQnEhFQnM= X-Received: from tj-virt.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5683]) (user=tjmercier job=sendgmr) by 2002:a05:6902:f85:b0:de6:166f:3250 with SMTP id 3f1490d57ef6-df7721c1a20mr3534064276.2.1716914254444; Tue, 28 May 2024 09:37:34 -0700 (PDT) Date: Tue, 28 May 2024 16:37:12 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.1.288.g0e0cd299f1-goog Message-ID: <20240528163713.2024887-1-tjmercier@google.com> Subject: [PATCH 1/2] cgroup: Fix /proc/cgroups count for v2 From: "T.J. Mercier" To: tjmercier@google.com, mkoutny@suse.com, Tejun Heo , Zefan Li , Johannes Weiner Cc: shakeel.butt@linux.dev, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" The /proc/cgroups documentation says that the num_cgroups value is, "the number of control groups in this hierarchy using this controller." The value printed is simply the total number of cgroups in the hierarchy which is correct for v1, but not for the shared v2 hierarchy. Consider: controllers="cpuset cpu io memory hugetlb pids rdma misc" for c in $controllers do echo +$c > /sys/fs/cgroup/cgroup.subtree_control mkdir /sys/fs/cgroup/$c echo +$c > /sys/fs/cgroup/$c/cgroup.subtree_control for i in `seq 100`; do mkdir /sys/fs/cgroup/$c/$i; done done cat /proc/cgroups cpuset 0 809 1 cpu 0 809 1 cpuacct 0 809 1 blkio 0 809 1 memory 0 809 1 devices 0 809 1 freezer 0 809 1 net_cls 0 809 1 perf_event 0 809 1 net_prio 0 809 1 hugetlb 0 809 1 pids 0 809 1 rdma 0 809 1 misc 0 809 1 debug 0 809 1 A count of 809 is reported for each controller, but only 109 should be reported for most of them since each controller is enabled in only part of the hierarchy. (Note that io depends on memcg, so its count should be 209.) The number of cgroups using a controller is an important metric since kernel memory is used for each cgroup, and some kernel operations scale with the number of cgroups for some controllers (memory, io). So users have an interest in minimizing/tracking the number of them. Signed-off-by: T.J. Mercier --- Changes from RFC: Don't manually initialize the atomic counters to 0 since they are kzalloced - Michal Koutny Also return the CSS count for utility controllers instead of the cgroup count - Michal Koutny include/linux/cgroup-defs.h | 6 ++++++ kernel/cgroup/cgroup-v1.c | 8 ++++++-- kernel/cgroup/cgroup.c | 2 ++ 3 files changed, 14 insertions(+), 2 deletions(-) diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index ea48c861cd36..bc1dbf7652c4 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -579,6 +579,12 @@ struct cgroup_root { /* Number of cgroups in the hierarchy, used only for /proc/cgroups */ atomic_t nr_cgrps; + /* + * Number of cgroups using each controller. Includes online and zombies. + * Used only for /proc/cgroups. + */ + atomic_t nr_css[CGROUP_SUBSYS_COUNT]; + /* Hierarchy-specific flags */ unsigned int flags; diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index b9dbf6bf2779..9bad59486c46 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -675,11 +675,15 @@ int proc_cgroupstats_show(struct seq_file *m, void *v) * cgroup_mutex contention. */ - for_each_subsys(ss, i) + for_each_subsys(ss, i) { + int count = cgroup_on_dfl(&ss->root->cgrp) ? + atomic_read(&ss->root->nr_css[i]) : atomic_read(&ss->root->nr_cgrps); + seq_printf(m, "%s\t%d\t%d\t%d\n", ss->legacy_name, ss->root->hierarchy_id, - atomic_read(&ss->root->nr_cgrps), + count, cgroup_ssid_enabled(i)); + } return 0; } diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index e32b6972c478..1bacd7cf7551 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5362,6 +5362,7 @@ static void css_free_rwork_fn(struct work_struct *work) ss->css_free(css); cgroup_idr_remove(&ss->css_idr, id); cgroup_put(cgrp); + atomic_dec(&ss->root->nr_css[ss->id]); if (parent) css_put(parent); @@ -5504,6 +5505,7 @@ static int online_css(struct cgroup_subsys_state *css) atomic_inc(&css->online_cnt); if (css->parent) atomic_inc(&css->parent->online_cnt); + atomic_inc(&ss->root->nr_css[ss->id]); } return ret; } base-commit: 6fbf71854e2ddea7c99397772fbbb3783bfe15b5 -- 2.45.1.288.g0e0cd299f1-goog