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[209.132.183.28]) by mx.google.com with ESMTPS id n1si7914371qkd.107.2019.06.17.07.50.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 17 Jun 2019 07:50:40 -0700 (PDT) Received-SPF: pass (google.com: domain of longman@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of longman@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=longman@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2823DC02938A; Mon, 17 Jun 2019 14:50:26 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-85.bos.redhat.com [10.18.17.85]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8730B7DF71; Mon, 17 Jun 2019 14:50:23 +0000 (UTC) Subject: Re: [PATCH] mm, memcg: Report number of memcg caches in slabinfo To: Michal Hocko Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Roman Gushchin , Johannes Weiner , Shakeel Butt , Vladimir Davydov , linux-api@vger.kernel.org References: <20190617142149.5245-1-longman@redhat.com> <20190617143842.GC1492@dhcp22.suse.cz> From: Waiman Long Organization: Red Hat Message-ID: <9e165eae-e354-04c4-6362-0f80fe819469@redhat.com> Date: Mon, 17 Jun 2019 10:50:23 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190617143842.GC1492@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 17 Jun 2019 14:50:39 +0000 (UTC) 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: On 6/17/19 10:38 AM, Michal Hocko wrote: > [Cc linux-api] > > On Mon 17-06-19 10:21:49, Waiman Long wrote: >> There are concerns about memory leaks from extensive use of memory >> cgroups as each memory cgroup creates its own set of kmem caches. There >> is a possiblity that the memcg kmem caches may remain even after the >> memory cgroup removal. >> >> Therefore, it will be useful to show how many memcg caches are present >> for each of the kmem caches. > How is a user going to use that information? Btw. Don't we have an > interface to display the number of (dead) cgroups? The interface to report dead cgroups is for cgroup v2 (cgroup.stat) only. I don't think there is a way to find that for cgroup v1. Also the number of memcg kmem caches may not be the same as the number of memcg's. It can range from 0 to above the number of memcg's.  So it is an interesting number by itself. >From the user perspective, if the numbers is way above the number of memcg's, there is probably something wrong there. Cheers, Longman