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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 73BF8C33CB1 for ; Fri, 17 Jan 2020 06:44:19 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2F44B20730 for ; Fri, 17 Jan 2020 06:44:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aAPD9+43" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2F44B20730 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A63946B0321; Fri, 17 Jan 2020 01:44:18 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A15256B0322; Fri, 17 Jan 2020 01:44:18 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 903C96B0323; Fri, 17 Jan 2020 01:44:18 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0131.hostedemail.com [216.40.44.131]) by kanga.kvack.org (Postfix) with ESMTP id 75DFC6B0321 for ; Fri, 17 Jan 2020 01:44:18 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 427E6180AD811 for ; Fri, 17 Jan 2020 06:44:18 +0000 (UTC) X-FDA: 76386186996.04.music68_429cecb216b12 X-HE-Tag: music68_429cecb216b12 X-Filterd-Recvd-Size: 3872 Received: from mail-pj1-f41.google.com (mail-pj1-f41.google.com [209.85.216.41]) by imf32.hostedemail.com (Postfix) with ESMTP for ; Fri, 17 Jan 2020 06:44:17 +0000 (UTC) Received: by mail-pj1-f41.google.com with SMTP id n96so2713221pjc.3 for ; Thu, 16 Jan 2020 22:44:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:subject:message-id:mime-version:content-disposition :user-agent; bh=hwfft8HwQOScDnCJrTR5hM4HJ298YsO1ivEEYtTm2Qc=; b=aAPD9+43z/qra4Ne7EBhN9KeMSptvDn2lV5OCHQlR4n7qJiFp4zjaJ/5+uqXINMEsy Vq3mYSLmFSGpDclIglu0b4ASfoybGMS2D6bRdorDbEd+TBWm5cMxwXGfLdWzu+87lvec h7x0jwMfRo23l7txZfvkzlZDEVdKzRV2FF3/rlb6RgFGTpZC9XqbtjoYXwFOqo8tt8/J XmL3M1wuwufkOjusCms1cJXI0uvheqvmag56muMzj6XvbIBJTBLiyXGPORMPaw8WOHtg mc3F2KFEEA/CEe9jlmbVRvJ5INk/n3Jz8FhE6h/FLaQwwnxz/RlbJwrDBHRpkIPf/fi+ kunQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:mime-version :content-disposition:user-agent; bh=hwfft8HwQOScDnCJrTR5hM4HJ298YsO1ivEEYtTm2Qc=; b=q9NYLQDx6GrEp63gU2hYD1W4nE9fXs0GbHz283QRln8C8h/AFrtRl8WhGjf4aZFtfo R9CVzPcm7zk3Eso4P8tHaxawq+1Inxs8d1wfWKTv2EK9sJkEi9v3XtY5ZXDAVX92hyYA A3Kq5eNxwJZ+V1XZj2RzmMMN7tJwhAeF1QlyvhShzcqKc/0tVTkn7MF1fW8WpDvx7UkN UMAwa/JC67BLCROEsVC4QYsBTdmvYaWyu0I8mxAwphWVyjmcD9CDQi9n9kxF07G26uX4 VRLHqHaTOyMBCDqIpOYdOGtS2sQwOoHLtFSuIxO3vRiRGE5oWZE3ISanzfMfg02bkKsg NxnQ== X-Gm-Message-State: APjAAAXkYHpVSGlro+SZA3aDk5BERCxlsSXsi3IW7QtZSw1uB5j12VeX i8ePDOZqTF9pvC0ev+Uc1QkJ2jtm X-Google-Smtp-Source: APXvYqx47OPNee5xitUXkJ0ZkyMXMhesU733HgpG5oiPDk4M1o7FdluyClCqL+4N6SGGWjWdKP913w== X-Received: by 2002:a17:90a:3aaf:: with SMTP id b44mr3995873pjc.9.1579243456337; Thu, 16 Jan 2020 22:44:16 -0800 (PST) Received: from haolee.github.io ([2600:3c01::f03c:91ff:fe02:b162]) by smtp.gmail.com with ESMTPSA id n24sm27967993pff.12.2020.01.16.22.44.15 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jan 2020 22:44:16 -0800 (PST) Date: Fri, 17 Jan 2020 06:44:14 +0000 From: Hao Lee To: linux-mm@kvack.org Subject: node_pagecache_reclaimable() seems not accurate Message-ID: <20200117064414.GA22642@haolee.github.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.12.1 (2019-06-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, I have found the node_pagecache_reclaimable() function can't calculate reclaimable pages accurately. If reclaim mode doesn't allow UNMAP and WRITE operations, this function will perform the following calculation: reclaimable file pages = total unmapped file pages - vm_stat[NR_FILE_DIRTY] If NR_FILE_DIRTY only counts unmapped dirty pages, the result will be unmapped clean pages. This indeed makes sense. However, I find vm_stat[NR_FILE_DIRTY] also counts some *mapped* dirty pages. If we subtract these mapped pages from unmapped pages, I don't think this is reasonable. This code path can account dirty pages into NR_FILE_DIRTY: account_page_dirtied+0x0/0x2d8 mark_buffer_dirty+0x16c/0x1a0 __block_commit_write.isra.11+0xa8/0xf0 block_write_end+0x58/0xb0 generic_write_end+0x5c/0xc0 ext4_da_write_end+0x128/0x2e8 [ext4] generic_perform_write+0x108/0x1a8 __generic_file_write_iter+0x158/0x1c8 ext4_file_write_iter+0x120/0x3e8 [ext4] __vfs_write+0x11c/0x190 vfs_write+0xac/0x1c0 ksys_write+0x74/0xf0 __arm64_sys_write+0x24/0x30 el0_svc_common+0x78/0x130 el0_svc_handler+0x38/0x78 el0_svc+0x8/0xc Regards, Hao Lee