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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 9A788C2BA83 for ; Thu, 13 Feb 2020 17:11:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D90A9206DB for ; Thu, 13 Feb 2020 17:10:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D90A9206DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8C8006B058A; Thu, 13 Feb 2020 12:10:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 877886B058B; Thu, 13 Feb 2020 12:10:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7B50F6B058C; Thu, 13 Feb 2020 12:10:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0189.hostedemail.com [216.40.44.189]) by kanga.kvack.org (Postfix) with ESMTP id 636C36B058A for ; Thu, 13 Feb 2020 12:10:59 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 07431181AEF15 for ; Thu, 13 Feb 2020 17:10:59 +0000 (UTC) X-FDA: 76485743838.13.wall29_5c15e095cd558 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id DA83318140B99 for ; Thu, 13 Feb 2020 17:07:16 +0000 (UTC) X-HE-Tag: wall29_5c15e095cd558 X-Filterd-Recvd-Size: 1776 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Thu, 13 Feb 2020 17:07:12 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R391e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04396;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=2;SR=0;TI=SMTPD_---0Tpuiwn0_1581613620; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0Tpuiwn0_1581613620) by smtp.aliyun-inc.com(127.0.0.1); Fri, 14 Feb 2020 01:07:02 +0800 To: "linux-mm@kvack.org" , linux-kernel From: Yang Shi Subject: [Question] Why PageReadahead is not migrated by migration code? Message-ID: <7691ab12-2e84-2531-f27d-2fae9045576d@linux.alibaba.com> Date: Thu, 13 Feb 2020 09:06:58 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Bogosity: Ham, tests=bogofilter, spamicity=0.097812, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi folks, Recently we saw some PageReadahead related bugs, so I did a quick check about the use of PageReadahead. I just found the state is *not* migrated by migrate_page_states(). Since migrate_page() won't migrate writeback page, so if PageReadahead is set it should just mean PG_readahead rather than PG_reclaim. So, I didn't think of why it is not migrated. I dig into the history a little bit, but the change in migration code is too overwhelming. But, it looks PG_readahead was added after migration was introduced. Is it just a simple omission? Thanks, Yang