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 0F2DDC433EF for ; Wed, 20 Jul 2022 07:02:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 39BDE6B0072; Wed, 20 Jul 2022 03:02:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 34A5D6B0073; Wed, 20 Jul 2022 03:02:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2121C6B0074; Wed, 20 Jul 2022 03:02:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 1616F6B0072 for ; Wed, 20 Jul 2022 03:02:00 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id E01DC404E5 for ; Wed, 20 Jul 2022 07:01:59 +0000 (UTC) X-FDA: 79706583558.13.3D61869 Received: from mail-pl1-f170.google.com (mail-pl1-f170.google.com [209.85.214.170]) by imf29.hostedemail.com (Postfix) with ESMTP id 8A132120086 for ; Wed, 20 Jul 2022 07:01:59 +0000 (UTC) Received: by mail-pl1-f170.google.com with SMTP id y24so903617plh.7 for ; Wed, 20 Jul 2022 00:01:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:from:to:cc:subject:references:mime-version :content-disposition:in-reply-to; bh=Lujkhd3wY54wcb90SIT8uAOyFvI2Fm968wecBcqgYO4=; b=O8m4GMS4UK9s9FeDbNMv5PS6p/Ss837cA1pqIsg6ExRq1N/qT/KEfcWnN0mhha+CnJ aNmEGe0yMPtWDFCCOZXNCIGa3knFUPK57+NhK5KnDIsz6KrqQ9HRu54T0GxVqMji7CYy utscfe0VBdQu/yr+vNhy1YmBwvlPutdJsRI2v8YhdPKu/Xp9MP1BRVeF4ZgjONqxDv4J C5Qg+Eyu2kYIYjL2Ws18BssbL8E+YJ16AH87x12/KKLk7TaONBkIGP01ICOgJrd9yHue VE9O+7dePHqamAsuP9TqbLg649OcK3u8D/VrDtwYo801RrxKhkRbNyBSkHKlM7ESE9Qu 1V+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:from:to:cc:subject:references :mime-version:content-disposition:in-reply-to; bh=Lujkhd3wY54wcb90SIT8uAOyFvI2Fm968wecBcqgYO4=; b=mg8fPEw7WlkftcsSK/Kt+OR+105+RvN6oRDteTiYLiq43qDJjF7Kgcb5OD/JoLsDhm OUH+5jVnOFe+B1InNySUfP9Cu4EM4iB0mYN7C2tUfro4ke0IH4MbKat1wgprnhNjSn1s k/TdCB+iFffYzZt8Q+sllGzgl3c9XXZz5IOxd6C/XkGtIi2qykhFW8DzlJTvskjbYJDw iuIs8Q8rlyXksCqQnGpMSUdoJtHKvq/1G3mVqMp6IZ3zxdt0j934gRfr1FbxqydTmHlC 1EzZrbdk9CIwsc/bdgBK4Rw7rfG+hzvYGhlq0lrKRA6lCCRtcbrNE4RUh8/sBdAbC1Ip /t7w== X-Gm-Message-State: AJIora97HfnIJt0DvlLe7gGdQUa2W7fgUURXosvUaPATvYOKNn30OQ/V luSBadgTf/O/Dsi7VszpHOk= X-Google-Smtp-Source: AGRyM1sVVTbH4ksSo3N4xkGw2M2P6n7iDsshnn0P6s/BAqZ6bIG4+PkpfkMBQM8CZgfWDojYn7MCqw== X-Received: by 2002:a17:90b:38c1:b0:1f1:f1c1:469c with SMTP id nn1-20020a17090b38c100b001f1f1c1469cmr3748928pjb.106.1658300518545; Wed, 20 Jul 2022 00:01:58 -0700 (PDT) Received: from localhost ([193.203.214.57]) by smtp.gmail.com with ESMTPSA id ij20-20020a170902ab5400b0016d02b0fa25sm761179plb.164.2022.07.20.00.01.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Jul 2022 00:01:57 -0700 (PDT) Message-ID: <62d7a865.1c69fb81.76782.1476@mx.google.com> X-Google-Original-Message-ID: <20220720070156.GA1497135@cgel.zte@gmail.com> Date: Wed, 20 Jul 2022 07:01:56 +0000 From: CGEL To: Christoph Hellwig Cc: Matthew Wilcox , viro@zeniv.linux.org.uk, hughd@google.com, akpm@linux-foundation.org, hsiangkao@linux.alibaba.com, yang.yang29@zte.com.cn, axboe@kernel.dk, yangerkun@huawei.com, johannes.thumshirn@wdc.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ran Xiaokai Subject: Re: [PATCH] fs: drop_caches: skip dropping pagecache which is always dirty References: <20220720022118.1495752-1-yang.yang29@zte.com.cn> <62d79a79.1c69fb81.e4cba.37f5@mx.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658300519; a=rsa-sha256; cv=none; b=sIVWFSoBycQ5kwOUifl6FJMRSZHKbdlAbqKcLNHm7d3je640J0ZZHZlrOZ/rX/DJ+A4vww WXU6yhI0RLujmCZH9/UOSoEmxuvR8w2X7jq7Yr9aWrdzS8etwbEMI37UG8vIXQsiLRYfqD DjcVeI6nI4bxYIlEj6+uRECjZm+1obk= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=O8m4GMS4; spf=pass (imf29.hostedemail.com: domain of cgel.zte@gmail.com designates 209.85.214.170 as permitted sender) smtp.mailfrom=cgel.zte@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658300519; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Lujkhd3wY54wcb90SIT8uAOyFvI2Fm968wecBcqgYO4=; b=0n57EdrEVOXgL6fbMJ7+Ja+6RFPFhtZQ+NowUslCaDD9xi/XgOXB2qhxcIka7vNvEJ3hqd dKd/BIfNOjxnbjxx0x+rr2PwEnomsFoaQLFecW5JCryqTbxJk2nu7SIZCUL7GRbxNqCEn6 Ok30snxqRr8q7jT3xxGfj1nfidEBvRE= X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8A132120086 Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=O8m4GMS4; spf=pass (imf29.hostedemail.com: domain of cgel.zte@gmail.com designates 209.85.214.170 as permitted sender) smtp.mailfrom=cgel.zte@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Stat-Signature: ikdygnq95w9xik9u517mn9pg3ohiw3yx X-HE-Tag: 1658300519-268133 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 19, 2022 at 11:04:36PM -0700, Christoph Hellwig wrote: > On Wed, Jul 20, 2022 at 06:02:32AM +0000, CGEL wrote: > > For example, some systems will create a lot of pagecache when boot up > > while reading bzImage, ramdisk, docker images etc. Most of this pagecache > > is useless after boot up. It may has a longterm negative effects for the > > workload when trigger page reclaim. It is especially harmful when trigger > > direct_reclaim or we need allocate pages in atomic context. So users may > > chose to drop_caches after boot up. > > It is purely a debug interface. If you want to drop specific page cache > that needs to be done through madvise. It's not easy for users to use madvise in complex system, it takes cost. Since drop_caches is not forbidden, and users may want simply use it in the scene above mail described.