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=-5.2 required=3.0 tests=BAYES_00, 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 3A657C433E1 for ; Fri, 10 Jul 2020 14:24:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 04A3A20674 for ; Fri, 10 Jul 2020 14:24:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 04A3A20674 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 78C708D0003; Fri, 10 Jul 2020 10:24:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 73CAD8D0001; Fri, 10 Jul 2020 10:24:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 653D48D0003; Fri, 10 Jul 2020 10:24:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0043.hostedemail.com [216.40.44.43]) by kanga.kvack.org (Postfix) with ESMTP id 4FB508D0001 for ; Fri, 10 Jul 2020 10:24:57 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B8D2B8248047 for ; Fri, 10 Jul 2020 14:24:56 +0000 (UTC) X-FDA: 77022387792.21.camp21_5b0cb5c26ecf Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id 7E69F180442D3 for ; Fri, 10 Jul 2020 14:24:56 +0000 (UTC) X-HE-Tag: camp21_5b0cb5c26ecf X-Filterd-Recvd-Size: 2506 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Fri, 10 Jul 2020 14:24:55 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04397;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U2Io76-_1594391084; Received: from IT-FVFX43SYHV2H.lan(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U2Io76-_1594391084) by smtp.aliyun-inc.com(127.0.0.1); Fri, 10 Jul 2020 22:24:45 +0800 Subject: Re: a question of split_huge_page To: "Kirill A. Shutemov" Cc: Matthew Wilcox , Johannes Weiner , Linux-MM , "linux-kernel@vger.kernel.org" , Hugh Dickins References: <20200709155002.GF12769@casper.infradead.org> <20200709160750.utl46xvavceuvnom@box> <20200710103318.bm2gp743lagiajao@box> From: Alex Shi Message-ID: Date: Fri, 10 Jul 2020 22:23:57 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200710103318.bm2gp743lagiajao@box> Content-Type: text/plain; charset=utf-8 X-Rspamd-Queue-Id: 7E69F180442D3 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 Content-Transfer-Encoding: quoted-printable 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: =E5=9C=A8 2020/7/10 =E4=B8=8B=E5=8D=886:33, Kirill A. Shutemov =E5=86=99=E9= =81=93: > On Fri, Jul 10, 2020 at 12:51:58PM +0800, Alex Shi wrote: >> >> >> =E5=9C=A8 2020/7/10 =E4=B8=8A=E5=8D=8812:07, Kirill A. Shutemov =E5=86= =99=E9=81=93: >>> Right, and it's never got removed from LRU during the split. The tail >>> pages have to be added to LRU because they now separate from the tail >>> page. >>> >> According to the explaination, looks like we could remove the code pat= h, >> since it's never got into. (base on my v15 patchset). Any comments? >=20 > Yes. But why? It's reasonable failsafe that gives chance to recover if > something goes wrong. >=20 Hi Kirill, Sorry, I didn't get your points. IMHO, this fallback cann't work well, since the head page isn't and shouldn't be added to lru. like the iommu i= ssue if a dma page added into lru list, it may be reclaim and lost. So, sorry,= I still don't know how this path could fix some wrong. Thanks Alex