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 645C5C433B4 for ; Fri, 9 Apr 2021 07:36:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D1E661179 for ; Fri, 9 Apr 2021 07:36:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231699AbhDIHgs (ORCPT ); Fri, 9 Apr 2021 03:36:48 -0400 Received: from out20-99.mail.aliyun.com ([115.124.20.99]:54380 "EHLO out20-99.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229621AbhDIHgq (ORCPT ); Fri, 9 Apr 2021 03:36:46 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.04104832|-1;CH=green;DM=|CONTINUE|false|;DS=CONTINUE|ham_regular_dialog|0.149414-0.00545288-0.845133;FP=0|0|0|0|0|-1|-1|-1;HT=ay29a033018047212;MF=wangyugui@e16-tech.com;NM=1;PH=DS;RN=5;RT=5;SR=0;TI=SMTPD_---.JxKNou3_1617953791; Received: from 192.168.2.112(mailfrom:wangyugui@e16-tech.com fp:SMTPD_---.JxKNou3_1617953791) by smtp.aliyun-inc.com(10.147.42.253); Fri, 09 Apr 2021 15:36:31 +0800 Date: Fri, 09 Apr 2021 15:36:39 +0800 From: Wang Yugui To: Wang Yugui Subject: Re: unexpected -ENOMEM from percpu_counter_init() Cc: Dennis Zhou , Vlastimil Babka , linux-mm@kvack.org, linux-btrfs@vger.kernel.org In-Reply-To: <20210409120214.7BB6.409509F4@e16-tech.com> References: <20210409120214.7BB6.409509F4@e16-tech.com> Message-Id: <20210409153636.C53D.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, 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. 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