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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED 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 2B365C433ED for ; Fri, 9 Apr 2021 07:48:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3353610CF for ; Fri, 9 Apr 2021 07:48:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229803AbhDIHsT (ORCPT ); Fri, 9 Apr 2021 03:48:19 -0400 Received: from out20-75.mail.aliyun.com ([115.124.20.75]:48028 "EHLO out20-75.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbhDIHsS (ORCPT ); Fri, 9 Apr 2021 03:48:18 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.04501791|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_regular_dialog|0.141684-0.00314613-0.85517;FP=0|0|0|0|0|-1|-1|-1;HT=ay29a033018047203;MF=wangyugui@e16-tech.com;NM=1;PH=DS;RN=4;RT=4;SR=0;TI=SMTPD_---.JxL0YAj_1617954484; Received: from 192.168.2.112(mailfrom:wangyugui@e16-tech.com fp:SMTPD_---.JxL0YAj_1617954484) by smtp.aliyun-inc.com(10.147.41.158); Fri, 09 Apr 2021 15:48:04 +0800 Date: Fri, 09 Apr 2021 15:48:12 +0800 From: Wang Yugui To: Dennis Zhou , Vlastimil Babka , linux-mm@kvack.org, linux-btrfs@vger.kernel.org Subject: Re: unexpected -ENOMEM from percpu_counter_init() In-Reply-To: <20210409153636.C53D.409509F4@e16-tech.com> References: <20210409120214.7BB6.409509F4@e16-tech.com> <20210409153636.C53D.409509F4@e16-tech.com> Message-Id: <20210409154811.C541.409509F4@e16-tech.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.75.03 [en] Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Hi, Add top/free info when our applicaiton pipeline is running. > Hi, > > some question about workqueue for percpu. > > > > > > > > > And a question about this, > > > > > > > > upper caller: > > > > > > > > nofs_flag = memalloc_nofs_save(); > > > > > > > > ret = btrfs_drew_lock_init(&root->snapshot_lock); > > > > > > > > memalloc_nofs_restore(nofs_flag); > > > > > > > > > > The issue is here. nofs is set which means percpu attempts an atomic > > > > > allocation. If it cannot find anything already allocated it isn't happy. > > > > > This was done before memalloc_nofs_{save/restore}() were pervasive. > > > > > > > > > > Percpu should probably try to allocate some pages if possible even if > > > > > nofs is set. > > > > > > > > Should we check and pre-alloc memory inside memalloc_nofs_restore()? > > > > another memalloc_nofs_save() may come soon. > > > > > > > > something like this in memalloc_nofs_save()? > > > > if (pcpu_nr_empty_pop_pages[type] < PCPU_EMPTY_POP_PAGES_LOW) > > > > pcpu_schedule_balance_work(); > > > > > > > > > > Percpu does do this via a workqueue item. The issue is in v5.9 we > > > introduced 2 types of chunks. However, the free float page number was > > > for the total. So even if 1 chunk type dropped below, the other chunk > > > type might have enough pages. I'm queuing this for 5.12 and will send it > > > out assuming it does fix your problem. > > workqueue for percpu maybe not strong enough( not scheduled?) when high > CPU load? > > this is our application pipeline. > file_pre_process | > bwa.nipt xx | > samtools.nipt sort xx | > file_post_process > > file_pre_process/file_post_process is fast, so often are blocked by > pipe input/output. > > 'bwa.nipt xx' is a high-cpu-load, almost all of CPU cores. > > 'samtools.nipt sort xx' is a high-mem-load, it keep the input in memory. > if the memory is not enough, it will save all the buffer to temp file, > so it is sometimes high-IO-load too(write 60G or more to file). > > > xfstests(generic/476) is just high-IO-load, cpu/memory load is NOT high. > so xfstests(generic/476) maybe easy than our application pipeline. # nproc 40 # top top - 15:43:06 up 10:16, 1 user, load average: 41.39, 37.90, 35.98 Tasks: 488 total, 3 running, 485 sleeping, 0 stopped, 0 zombie %Cpu(s): 99.6 us, 0.1 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.3 hi, 0.0 si, 0.0 st MiB Mem : 58.3/193384.1 [|||||||||||||||||||||||||||||||||||||||||||||||||||||| ] MiB Swap: 0.0/0.0 [ ] # free -h total used free shared buff/cache available Mem: 188Gi 98Gi 5.8Gi 17Mi 84Gi 78Gi Swap: 0B 0B 0B memory reclaim from 'buff/cache' is easy to happen. Best Regards Wang Yugui (wangyugui@e16-tech.com) 2021/04/09 > Although there is yet not a simple reproducer for another problem > happend here, but there is a little high chance that something is wrong > in btrfs/mm/fs-buffer. > > but another problem(os freezed without call trace, PANIC without OOPS?, > > the reason is yet unkown) still happen. > > Best Regards > Wang Yugui (wangyugui@e16-tech.com) > 2021/04/09 >