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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2746ECAAD3 for ; Thu, 15 Sep 2022 08:02:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 140C58D0002; Thu, 15 Sep 2022 04:02:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0F0B26B0078; Thu, 15 Sep 2022 04:02:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ED37C8D0002; Thu, 15 Sep 2022 04:02:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id DAD426B0074 for ; Thu, 15 Sep 2022 04:02:49 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id AD49D80C71 for ; Thu, 15 Sep 2022 08:02:49 +0000 (UTC) X-FDA: 79913578458.16.033DB79 Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by imf01.hostedemail.com (Postfix) with ESMTP id 1836E400A5 for ; Thu, 15 Sep 2022 08:02:47 +0000 (UTC) Received: from [10.180.13.185] (unknown [10.180.13.185]) by localhost.localdomain (Coremail) with SMTP id AQAAf8CxT+Ah3CJjZO0ZAA--.35413S3; Thu, 15 Sep 2022 16:02:41 +0800 (CST) Subject: Re: [PATCH] mm/vmscan: don't scan adjust too much if current is not kswapd To: Matthew Wilcox Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220914023318.549118-1-zhanghongchen@loongson.cn> <20220914155142.bf388515a39fb45bae987231@linux-foundation.org> <6bcb4883-03d0-88eb-4c42-84fff0a9a141@loongson.cn> From: Hongchen Zhang Message-ID: <54813a74-cc0e-e470-c632-78437a0d0ad4@loongson.cn> Date: Thu, 15 Sep 2022 16:02:41 +0800 User-Agent: Mozilla/5.0 (X11; Linux loongarch64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; 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dkim=none; dmarc=none; spf=pass (imf01.hostedemail.com: domain of zhanghongchen@loongson.cn designates 114.242.206.163 as permitted sender) smtp.mailfrom=zhanghongchen@loongson.cn X-Rspam-User: X-Rspamd-Queue-Id: 1836E400A5 X-Rspamd-Server: rspam01 X-Stat-Signature: irpke4j3kss3qo4smsbghe9i7ez5o4jo X-HE-Tag: 1663228967-108312 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: Hi Matthew, On 2022/9/15 pm 3:28, Matthew Wilcox wrote: > On Thu, Sep 15, 2022 at 09:19:48AM +0800, Hongchen Zhang wrote: >> [ 3748.453561] INFO: task float_bessel:77920 blocked for more than 120 >> seconds. >> [ 3748.460839] Not tainted 5.15.0-46-generic #49-Ubuntu >> [ 3748.466490] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables >> this message. >> [ 3748.474618] task:float_bessel state:D stack: 0 pid:77920 ppid: >> 77327 flags:0x00004002 >> [ 3748.483358] Call Trace: >> [ 3748.485964] >> [ 3748.488150] __schedule+0x23d/0x590 >> [ 3748.491804] schedule+0x4e/0xc0 >> [ 3748.495038] rwsem_down_read_slowpath+0x336/0x390 >> [ 3748.499886] ? copy_user_enhanced_fast_string+0xe/0x40 >> [ 3748.505181] down_read+0x43/0xa0 >> [ 3748.508518] do_user_addr_fault+0x41c/0x670 >> [ 3748.512799] exc_page_fault+0x77/0x170 >> [ 3748.516673] asm_exc_page_fault+0x26/0x30 >> [ 3748.520824] RIP: 0010:copy_user_enhanced_fast_string+0xe/0x40 >> [ 3748.526764] Code: 89 d1 c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 31 c0 0f >> 01 ca c3 cc cc cc cc 0f 1f 00 0f 01 cb 83 fa 40 0f 82 70 ff ff ff 89 d1 >> a4 31 c0 0f 01 ca c3 cc cc cc cc 66 08 >> [ 3748.546120] RSP: 0018:ffffaa9248fffb90 EFLAGS: 00050206 >> [ 3748.551495] RAX: 00007f99faa1a010 RBX: ffffaa9248fffd88 RCX: >> 0000000000000010 >> [ 3748.558828] RDX: 0000000000001000 RSI: ffff9db397ab8ff0 RDI: >> 00007f99faa1a000 >> [ 3748.566160] RBP: ffffaa9248fffbf0 R08: ffffcc2fc2965d80 R09: >> 0000000000000014 >> [ 3748.573492] R10: 0000000000000000 R11: 0000000000000014 R12: >> 0000000000001000 >> [ 3748.580858] R13: 0000000000001000 R14: 0000000000000000 R15: >> ffffaa9248fffd98 >> [ 3748.588196] ? copy_page_to_iter+0x10e/0x400 >> [ 3748.592614] filemap_read+0x174/0x3e0 > > Interesting; it wasn't the process itself which triggered the page > fault; the process called read() and the kernel took the page fault to > satisfy the read() call. > >> [ 3748.596354] ? ima_file_check+0x6a/0xa0 >> [ 3748.600301] generic_file_read_iter+0xe5/0x150 >> [ 3748.604884] ext4_file_read_iter+0x5b/0x190 >> [ 3748.609164] ? aa_file_perm+0x102/0x250 >> [ 3748.613125] new_sync_read+0x10d/0x1a0 >> [ 3748.617009] vfs_read+0x103/0x1a0 >> [ 3748.620423] ksys_read+0x67/0xf0 >> [ 3748.623743] __x64_sys_read+0x19/0x20 >> [ 3748.627511] do_syscall_64+0x59/0xc0 >> [ 3748.631203] ? syscall_exit_to_user_mode+0x27/0x50 >> [ 3748.636144] ? do_syscall_64+0x69/0xc0 >> [ 3748.639992] ? exit_to_user_mode_prepare+0x96/0xb0 >> [ 3748.644931] ? irqentry_exit_to_user_mode+0x9/0x20 >> [ 3748.649872] ? irqentry_exit+0x1d/0x30 >> [ 3748.653737] ? exc_page_fault+0x89/0x170 >> [ 3748.657795] entry_SYSCALL_64_after_hwframe+0x61/0xcb >> [ 3748.663030] RIP: 0033:0x7f9a852989cc >> [ 3748.666713] RSP: 002b:00007f9a8497dc90 EFLAGS: 00000246 ORIG_RAX: >> 0000000000000000 >> [ 3748.674487] RAX: ffffffffffffffda RBX: 00007f9a8497f5c0 RCX: >> 00007f9a852989cc >> [ 3748.681817] RDX: 0000000000027100 RSI: 00007f99faa18010 RDI: >> 0000000000000061 >> [ 3748.689150] RBP: 00007f9a8497dd60 R08: 0000000000000000 R09: >> 00007f99faa18010 >> [ 3748.696493] R10: 0000000000000000 R11: 0000000000000246 R12: >> 00007f99faa18010 >> [ 3748.703841] R13: 00005605e11c406f R14: 0000000000000001 R15: >> 0000000000027100 > > ORIG_RAX is 0, which matches sys_read. > RDI is file descriptor 0x61 > RSI is plausibly a userspace pointer, 0x7f99faa18010 > RDX is the length, 0x27100 or 160kB. > > That all seems reasonable. > > What I really want to know is who is _holding_ the lock. We stash > a pointer to the task_struct in 'owner', so we could clearly find this > out in the 'blocked for too long' report, and print their stack trace. > As described in the comment for __rwsem_set_reader_owned,it is hard to track read owners.So we could not clearly find out who blocked the process,it was caused by multiple tasks. > You must have done something like this already in order to deduce that > it was the direct reclaim path that was the problem? > The method we used is to track the direct reclaim using the trace_mm_vmscan_direct_reclaim_{begin,end} interface.When the problem occurred,we could get a very large "nr_reclaimed" which is not a desirable value for process except kswapd. Thanks Hongchen Zhang