From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AE971C33CB2 for ; Thu, 30 Jan 2020 02:06:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F11C206F0 for ; Thu, 30 Jan 2020 02:06:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726771AbgA3CGj (ORCPT ); Wed, 29 Jan 2020 21:06:39 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:1882 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726632AbgA3CGj (ORCPT ); Wed, 29 Jan 2020 21:06:39 -0500 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 00U1xCOO011991 for ; Wed, 29 Jan 2020 21:06:37 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0b-001b2d01.pphosted.com with ESMTP id 2xtfh1dn6x-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 29 Jan 2020 21:06:37 -0500 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 30 Jan 2020 02:06:35 -0000 Received: from b06avi18626390.portsmouth.uk.ibm.com (9.149.26.192) by e06smtp07.uk.ibm.com (192.168.101.137) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 30 Jan 2020 02:06:32 -0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 00U25dMs47972700 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 30 Jan 2020 02:05:39 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1F4F04C04E; Thu, 30 Jan 2020 02:06:31 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EDD544C040; Thu, 30 Jan 2020 02:06:28 +0000 (GMT) Received: from in.ibm.com (unknown [9.199.51.93]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 30 Jan 2020 02:06:28 +0000 (GMT) Date: Thu, 30 Jan 2020 07:36:26 +0530 From: Bharata B Rao To: Roman Gushchin Cc: linux-mm@kvack.org, Andrew Morton , Michal Hocko , Johannes Weiner , Shakeel Butt , Vladimir Davydov , linux-kernel@vger.kernel.org, kernel-team@fb.com, Yafang Shao Subject: Re: [PATCH v2 00/28] The new cgroup slab memory controller Reply-To: bharata@linux.ibm.com References: <20200127173453.2089565-1-guro@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200127173453.2089565-1-guro@fb.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-TM-AS-GCONF: 00 x-cbid: 20013002-0028-0000-0000-000003D5A2F8 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20013002-0029-0000-0000-00002499EFF2 Message-Id: <20200130020626.GA21973@in.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-01-29_08:2020-01-28,2020-01-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxscore=0 lowpriorityscore=0 suspectscore=2 mlxlogscore=999 bulkscore=0 malwarescore=0 spamscore=0 phishscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1911200001 definitions=main-2001300011 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 27, 2020 at 09:34:25AM -0800, Roman Gushchin wrote: > The existing cgroup slab memory controller is based on the idea of > replicating slab allocator internals for each memory cgroup. > This approach promises a low memory overhead (one pointer per page), > and isn't adding too much code on hot allocation and release paths. > But is has a very serious flaw: it leads to a low slab utilization. > > Using a drgn* script I've got an estimation of slab utilization on > a number of machines running different production workloads. In most > cases it was between 45% and 65%, and the best number I've seen was > around 85%. Turning kmem accounting off brings it to high 90s. Also > it brings back 30-50% of slab memory. It means that the real price > of the existing slab memory controller is way bigger than a pointer > per page. > > The real reason why the existing design leads to a low slab utilization > is simple: slab pages are used exclusively by one memory cgroup. > If there are only few allocations of certain size made by a cgroup, > or if some active objects (e.g. dentries) are left after the cgroup is > deleted, or the cgroup contains a single-threaded application which is > barely allocating any kernel objects, but does it every time on a new CPU: > in all these cases the resulting slab utilization is very low. > If kmem accounting is off, the kernel is able to use free space > on slab pages for other allocations. > > Arguably it wasn't an issue back to days when the kmem controller was > introduced and was an opt-in feature, which had to be turned on > individually for each memory cgroup. But now it's turned on by default > on both cgroup v1 and v2. And modern systemd-based systems tend to > create a large number of cgroups. > > This patchset provides a new implementation of the slab memory controller, > which aims to reach a much better slab utilization by sharing slab pages > between multiple memory cgroups. Below is the short description of the new > design (more details in commit messages). > > Accounting is performed per-object instead of per-page. Slab-related > vmstat counters are converted to bytes. Charging is performed on page-basis, > with rounding up and remembering leftovers. > > Memcg ownership data is stored in a per-slab-page vector: for each slab page > a vector of corresponding size is allocated. To keep slab memory reparenting > working, instead of saving a pointer to the memory cgroup directly an > intermediate object is used. It's simply a pointer to a memcg (which can be > easily changed to the parent) with a built-in reference counter. This scheme > allows to reparent all allocated objects without walking them over and > changing memcg pointer to the parent. > > Instead of creating an individual set of kmem_caches for each memory cgroup, > two global sets are used: the root set for non-accounted and root-cgroup > allocations and the second set for all other allocations. This allows to > simplify the lifetime management of individual kmem_caches: they are > destroyed with root counterparts. It allows to remove a good amount of code > and make things generally simpler. > > The patchset* has been tested on a number of different workloads in our > production. In all cases it saved significant amount of memory, measured > from high hundreds of MBs to single GBs per host. On average, the size > of slab memory has been reduced by 35-45%. Here are some numbers from multiple runs of sysbench and kernel compilation with this patchset on a 10 core POWER8 host: ========================================================================== Peak usage of memory.kmem.usage_in_bytes, memory.usage_in_bytes and meminfo:Slab for Sysbench oltp_read_write with mysqld running as part of a mem cgroup (Sampling every 5s) -------------------------------------------------------------------------- 5.5.0-rc7-mm1 +slab patch %reduction -------------------------------------------------------------------------- memory.kmem.usage_in_bytes 15859712 4456448 72 memory.usage_in_bytes 337510400 335806464 .5 Slab: (kB) 814336 607296 25 memory.kmem.usage_in_bytes 16187392 4653056 71 memory.usage_in_bytes 318832640 300154880 5 Slab: (kB) 789888 559744 29 -------------------------------------------------------------------------- Peak usage of memory.kmem.usage_in_bytes, memory.usage_in_bytes and meminfo:Slab for kernel compilation (make -s -j64) Compilation was done from bash that is in a memory cgroup. (Sampling every 5s) -------------------------------------------------------------------------- 5.5.0-rc7-mm1 +slab patch %reduction -------------------------------------------------------------------------- memory.kmem.usage_in_bytes 338493440 231931904 31 memory.usage_in_bytes 7368015872 6275923968 15 Slab: (kB) 1139072 785408 31 memory.kmem.usage_in_bytes 341835776 236453888 30 memory.usage_in_bytes 6540427264 6072893440 7 Slab: (kB) 1074304 761280 29 memory.kmem.usage_in_bytes 340525056 233570304 31 memory.usage_in_bytes 6406209536 6177357824 3 Slab: (kB) 1244288 739712 40 -------------------------------------------------------------------------- Slab consumption right after boot -------------------------------------------------------------------------- 5.5.0-rc7-mm1 +slab patch %reduction -------------------------------------------------------------------------- Slab: (kB) 821888 583424 29 ========================================================================== Summary: With sysbench and kernel compilation, memory.kmem.usage_in_bytes shows around 70% and 30% reduction consistently. Didn't see consistent reduction of memory.usage_in_bytes with sysbench and kernel compilation. Slab usage (from /proc/meminfo) shows consistent 30% reduction and the same is seen right after boot too. Regards, Bharata.