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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 B686FC2BA19 for ; Tue, 21 Apr 2020 09:13:07 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 80AFC2087E for ; Tue, 21 Apr 2020 09:13:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 80AFC2087E 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 104F18E0005; Tue, 21 Apr 2020 05:13:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0B56A8E0003; Tue, 21 Apr 2020 05:13:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F0D5F8E0005; Tue, 21 Apr 2020 05:13:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0105.hostedemail.com [216.40.44.105]) by kanga.kvack.org (Postfix) with ESMTP id D6EC38E0003 for ; Tue, 21 Apr 2020 05:13:06 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 98AA08248D7C for ; Tue, 21 Apr 2020 09:13:06 +0000 (UTC) X-FDA: 76731297972.28.class49_382882dba0d0e X-HE-Tag: class49_382882dba0d0e X-Filterd-Recvd-Size: 2802 Received: from out4436.biz.mail.alibaba.com (out4436.biz.mail.alibaba.com [47.88.44.36]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Tue, 21 Apr 2020 09:13:05 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R961e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01358;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=11;SR=0;TI=SMTPD_---0TwDlbOU_1587460334; Received: from IT-FVFX43SYHV2H.local(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0TwDlbOU_1587460334) by smtp.aliyun-inc.com(127.0.0.1); Tue, 21 Apr 2020 17:12:17 +0800 Subject: Re: [PATCH 03/18] mm: memcontrol: drop @compound parameter from memcg charging API To: Johannes Weiner , Joonsoo Kim Cc: Shakeel Butt , Hugh Dickins , Michal Hocko , "Kirill A. Shutemov" , Roman Gushchin , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com References: <20200420221126.341272-1-hannes@cmpxchg.org> <20200420221126.341272-4-hannes@cmpxchg.org> From: Alex Shi Message-ID: <73c1a95f-fee9-716d-c72f-85585de13f2f@linux.alibaba.com> Date: Tue, 21 Apr 2020 17:11:08 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200420221126.341272-4-hannes@cmpxchg.org> Content-Type: text/plain; charset=gbk 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: =D4=DA 2020/4/21 =C9=CF=CE=E76:11, Johannes Weiner =D0=B4=B5=C0: > The memcg charging API carries a boolean @compound parameter that > tells whether the page we're dealing with is a hugepage. > mem_cgroup_commit_charge() has another boolean @lrucare that indicates > whether the page needs LRU locking or not while charging. The majority > of callsites know those parameters at compile time, which results in a > lot of naked "false, false" argument lists. This makes for cryptic > code and is a breeding ground for subtle mistakes. >=20 > Thankfully, the huge page state can be inferred from the page itself > and doesn't need to be passed along. This is safe because charging > completes before the page is published and somebody may split it. >=20 > Simplify the callsites by removing @compound, and let memcg infer the > state by using hpage_nr_pages() unconditionally. That function does > PageTransHuge() to identify huge pages, which also helpfully asserts > that nobody passes in tail pages by accident. >=20 > The following patches will introduce a new charging API, best not to > carry over unnecessary weight. >=20 > Signed-off-by: Johannes Weiner Reviewed-by: Alex Shi