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 8E432C433E4 for ; Fri, 10 Jul 2020 14:24:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 714BE206E2 for ; Fri, 10 Jul 2020 14:24:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728658AbgGJOY5 (ORCPT ); Fri, 10 Jul 2020 10:24:57 -0400 Received: from out4436.biz.mail.alibaba.com ([47.88.44.36]:59150 "EHLO out4436.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727941AbgGJOY5 (ORCPT ); Fri, 10 Jul 2020 10:24:57 -0400 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 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2020/7/10 下午6:33, Kirill A. Shutemov 写道: > On Fri, Jul 10, 2020 at 12:51:58PM +0800, Alex Shi wrote: >> >> >> 在 2020/7/10 上午12:07, Kirill A. Shutemov 写道: >>> 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 path, >> since it's never got into. (base on my v15 patchset). Any comments? > > Yes. But why? It's reasonable failsafe that gives chance to recover if > something goes wrong. > 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 issue 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