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 5C930C32771 for ; Fri, 16 Sep 2022 00:57:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DB9CC8D0003; Thu, 15 Sep 2022 20:57:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D68AC8D0001; Thu, 15 Sep 2022 20:57:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C08EB8D0003; Thu, 15 Sep 2022 20:57:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id AFCE38D0001 for ; Thu, 15 Sep 2022 20:57:55 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 892101C71DE for ; Fri, 16 Sep 2022 00:57:55 +0000 (UTC) X-FDA: 79916136510.13.E1BD06D Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by imf29.hostedemail.com (Postfix) with ESMTP id ABC7E1200E8 for ; Fri, 16 Sep 2022 00:57:53 +0000 (UTC) Received: from [10.180.13.185] (unknown [10.180.13.185]) by localhost.localdomain (Coremail) with SMTP id AQAAf8CxYOIOyiNjobUaAA--.38123S3; Fri, 16 Sep 2022 08:57:50 +0800 (CST) Subject: Re: [PATCH] mm/vmscan: don't scan adjust too much if current is not kswapd To: Andrew Morton Cc: Matthew Wilcox , 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> <54813a74-cc0e-e470-c632-78437a0d0ad4@loongson.cn> From: Hongchen Zhang Message-ID: Date: Fri, 16 Sep 2022 08:57:50 +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; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-CM-TRANSID:AQAAf8CxYOIOyiNjobUaAA--.38123S3 X-Coremail-Antispam: 1UD129KBjvJXoW3WF4UKF45KrW5Kw1UGw4Uurg_yoW7Cr1rpF 15tFZrKF4kJr4Utr4UKw4vqr109F1DC3W5WryrGrnruF1jvwn8J3y8Gr45K3W3Jr1Uurya qrW5Xw12vr17JaUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvYb7Iv0xC_Kw4lb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I2 0VC2zVCF04k26cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rw A2F7IY1VAKz4vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Gr0_Xr1l84ACjcxK6xII jxv20xvEc7CjxVAFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVAFwI0_Cr0_Gr1UM28EF7xvwV C2z280aVCY1x0267AKxVW8Jr0_Cr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVAC Y4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJV W8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lc7I2V7IY0VAS07AlzVAYIcxG 8wCY02Avz4vE-syl42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxV Aqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r12 6r1DMIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6x kF7I0E14v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AK xVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0xZFpf9x07 bOoGdUUUUU= X-CM-SenderInfo: x2kd0w5krqwupkhqwqxorr0wxvrqhubq/ ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=none; spf=pass (imf29.hostedemail.com: domain of zhanghongchen@loongson.cn designates 114.242.206.163 as permitted sender) smtp.mailfrom=zhanghongchen@loongson.cn; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663289875; a=rsa-sha256; cv=none; b=3+NcHALbJ9K7FkiZylQfIZu/qXvU5b2NCwHI95/krmm0S5H/itOUZ+8DKBlXAzPlYlpHGd hIfWaAxSVXRdNdQ7gR20rC0JpqQH2IswrgKphfoz/ZDJv9iusssm9rL0Um/BsCTno7cxcI V4AJpSW+av1MS5MVBspa0Gn7sDTdCyo= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663289875; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=saEcPTSKB6fzhsTNcUDYDTgrkUWoiSm/uzGsr/hiGuw=; b=tBA+u1WN2Bkgnbt3dc9ipbh9qW9Fcx555U8lq3FCM6Jec9qUlQsEK7q4IqpPhjCaCZfzh9 f/MMkNkrMnh+UrMrFrtuqN6/o8albEXFnKkJOHlUJeGgyqGHYi+si3ZMUNdoabWs508aGH gSYaMeYXDYXgGlpxGv1nOnd9eobGZnk= X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: ABC7E1200E8 Authentication-Results: imf29.hostedemail.com; dkim=none; spf=pass (imf29.hostedemail.com: domain of zhanghongchen@loongson.cn designates 114.242.206.163 as permitted sender) smtp.mailfrom=zhanghongchen@loongson.cn; dmarc=none X-Stat-Signature: rwr6o5i6ybkuug5xziw39yayee8z99fj X-HE-Tag: 1663289873-484947 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 Andrew , On 2022/9/15 pm 5:00, Matthew Wilcox wrote: > On Thu, Sep 15, 2022 at 04:02:41PM +0800, Hongchen Zhang wrote: >> 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. > > Readers don't block readers. You have a reader here, so it's being > blocked by a writer. And that writer's task_struct is stashed in > rwsem->owner. It would be nice if we dumped that information > automatically ... but we don't do that today. Perhaps you could > grab that information from a crash dump if you have one. > >>> 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. > > I disagree. If a process needs to allocate memory then it should be > paying the cost of reclaiming that memory itself. kswapd is a last > resort to reclaim memory when we have a workload (eg a network router) > that does its memory allocation primarily in interrupt context. > What's your opinion about this scan adjust issue? Is there a better way to fix this issue? Thanks Hongchen Zhang