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=-14.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 2066EC433E2 for ; Wed, 24 Mar 2021 19:07:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD53A61A16 for ; Wed, 24 Mar 2021 19:07:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237833AbhCXTHF (ORCPT ); Wed, 24 Mar 2021 15:07:05 -0400 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:55588 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237730AbhCXTGg (ORCPT ); Wed, 24 Mar 2021 15:06:36 -0400 Received: from pps.filterd (m0044010.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 12OJ4wiD000640 for ; Wed, 24 Mar 2021 12:06:36 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-transfer-encoding : content-type; s=facebook; bh=hZDBTvWEE01rM4Olmsjdj7mKlECbbT1uO9DrFO8s5zU=; b=jb6MOg648M9c1gAOlL8XNFA5X8dBApLRffgiFw/Je0pfWpgaljHbOHI092mmzt5EOU1G bah5GgnCvUUDgClckwiCJ5oRyHc+FrYC/OmyyOWIwcXkyVqjI16UZTMsIEk5TkzX67Sk uyEeUUHi/i+5U4ja0LYj/Pixm5LLUwACqQk= Received: from mail.thefacebook.com ([163.114.132.120]) by mx0a-00082601.pphosted.com with ESMTP id 37fpjt6t8a-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Wed, 24 Mar 2021 12:06:35 -0700 Received: from intmgw003.48.prn1.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:21d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Wed, 24 Mar 2021 12:06:35 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 8022657ACF28; Wed, 24 Mar 2021 12:06:33 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , , , Roman Gushchin Subject: [PATCH rfc 0/4] percpu: partial chunk depopulation Date: Wed, 24 Mar 2021 12:06:22 -0700 Message-ID: <20210324190626.564297-1-guro@fb.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-03-24_13:2021-03-24,2021-03-24 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 phishscore=0 priorityscore=1501 mlxlogscore=954 lowpriorityscore=0 spamscore=0 clxscore=1015 bulkscore=0 suspectscore=0 mlxscore=0 malwarescore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103240137 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In our production experience the percpu memory allocator is sometimes str= uggling with returning the memory to the system. A typical example is a creation = of several thousands memory cgroups (each has several chunks of the percpu d= ata used for vmstats, vmevents, ref counters etc). Deletion and complete rele= asing of these cgroups doesn't always lead to a shrinkage of the percpu memory. The underlying problem is the fragmentation: to release an underlying chu= nk all percpu allocations should be released first. The percpu allocator ten= ds to top up chunks to improve the utilization. It means new small-ish alloc= ations (e.g. percpu ref counters) are placed onto almost filled old-ish chunks, effectively pinning them in memory. This patchset pretends to solve this problem by implementing a partial depopulation of percpu chunks: chunks with many empty pages are being asynchronously depopulated and the pages are returned to the system. To illustrate the problem the following script can be used: -- #!/bin/bash cd /sys/fs/cgroup mkdir percpu_test echo "+memory" > percpu_test/cgroup.subtree_control cat /proc/meminfo | grep Percpu for i in `seq 1 1000`; do mkdir percpu_test/cg_"${i}" for j in `seq 1 10`; do mkdir percpu_test/cg_"${i}"_"${j}" done done cat /proc/meminfo | grep Percpu for i in `seq 1 1000`; do for j in `seq 1 10`; do rmdir percpu_test/cg_"${i}"_"${j}" done done sleep 10 cat /proc/meminfo | grep Percpu for i in `seq 1 1000`; do rmdir percpu_test/cg_"${i}" done rmdir percpu_test -- It creates 11000 memory cgroups and removes every 10 out of 11. It prints the initial size of the percpu memory, the size after creating all cgroups and the size after deleting most of them. Results: vanilla: $ ./percpu_test.sh Percpu: 7296 kB Percpu: 481024 kB Percpu: 481024 kB with this patchset applied: ./percpu_test.sh Percpu: 7488 kB Percpu: 481152 kB Percpu: 153920 kB So the total size of the percpu memory was reduced by ~3 times. Roman Gushchin (4): percpu: implement partial chunk depopulation percpu: split __pcpu_balance_workfn() percpu: on demand chunk depopulation percpu: fix a comment about the chunks ordering mm/percpu-internal.h | 1 + mm/percpu.c | 242 ++++++++++++++++++++++++++++++++++++------- 2 files changed, 203 insertions(+), 40 deletions(-) --=20 2.30.2