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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 48417C56202 for ; Thu, 26 Nov 2020 11:22:34 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 88668206B7 for ; Thu, 26 Nov 2020 11:22:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 88668206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D24426B0072; Thu, 26 Nov 2020 06:22:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CD4FB6B0073; Thu, 26 Nov 2020 06:22:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C14486B0074; Thu, 26 Nov 2020 06:22:32 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0201.hostedemail.com [216.40.44.201]) by kanga.kvack.org (Postfix) with ESMTP id AC6A16B0072 for ; Thu, 26 Nov 2020 06:22:32 -0500 (EST) Received: from smtpin12.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 780433637 for ; Thu, 26 Nov 2020 11:22:32 +0000 (UTC) X-FDA: 77526331344.12.cars65_460a1a02737e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin12.hostedemail.com (Postfix) with ESMTP id 55BF218023F7B for ; Thu, 26 Nov 2020 11:22:32 +0000 (UTC) X-HE-Tag: cars65_460a1a02737e X-Filterd-Recvd-Size: 4011 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf50.hostedemail.com (Postfix) with ESMTP for ; Thu, 26 Nov 2020 11:22:31 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id B6E6AAC22; Thu, 26 Nov 2020 11:22:30 +0000 (UTC) To: Yu Zhao , Alex Shi Cc: Konstantin Khlebnikov , Andrew Morton , Hugh Dickins , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1605860847-47445-1-git-send-email-alex.shi@linux.alibaba.com> <20201126045234.GA1014081@google.com> <20201126072402.GA1047005@google.com> From: Vlastimil Babka Subject: Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add Message-ID: <464fa387-9dfd-a8c7-3d86-040f26fd4115@suse.cz> Date: Thu, 26 Nov 2020 12:22:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201126072402.GA1047005@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US 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: On 11/26/20 8:24 AM, Yu Zhao wrote: > On Thu, Nov 26, 2020 at 02:39:03PM +0800, Alex Shi wrote: >>=20 >>=20 >> =E5=9C=A8 2020/11/26 =E4=B8=8B=E5=8D=8812:52, Yu Zhao =E5=86=99=E9=81=93= : >> >> */ >> >> void __pagevec_lru_add(struct pagevec *pvec) >> >> { >> >> - int i; >> >> - struct lruvec *lruvec =3D NULL; >> >> + int i, nr_lruvec; >> >> unsigned long flags =3D 0; >> >> + struct page *page; >> >> + struct lruvecs lruvecs; >> >> =20 >> >> - for (i =3D 0; i < pagevec_count(pvec); i++) { >> >> - struct page *page =3D pvec->pages[i]; >> >> + nr_lruvec =3D sort_page_lruvec(&lruvecs, pvec); >> > Simply looping pvec multiple times (15 at most) for different lruvec= s >> > would be better because 1) it requires no extra data structures and >> > therefore has better cache locality (theoretically faster) 2) it onl= y >> > loops once when !CONFIG_MEMCG and !CONFIG_NUMA and therefore has no >> > impact on Android and Chrome OS. >> >=20 >>=20 >> With multiple memcgs, it do help a lot, I had gotten 30% grain on read= twice >> case. but yes, w/o MEMCG and NUMA, it's good to keep old behavior. So=20 >> would you like has a proposal for this? >=20 > Oh, no, I'm not against your idea. I was saying it doesn't seem > necessary to sort -- a nested loop would just do the job given > pagevec is small. Yeah that could work. The worst case doesn't look nice (O(n^2)) but it sh= ould be=20 rather rare to have pages from really multiple memcgs/nodes? Maybe with the following change? Avoids going through the nulls if we got= lucky=20 (or have !MEMCG !NUMA). > diff --git a/mm/swap.c b/mm/swap.c > index cb3794e13b48..1d238edc2907 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -996,15 +996,26 @@ static void __pagevec_lru_add_fn(struct page *pag= e, struct lruvec *lruvec) > */ > void __pagevec_lru_add(struct pagevec *pvec) > { > - int i; > + int i, j; int i, j, n; > struct lruvec *lruvec =3D NULL; > unsigned long flags =3D 0; > =20 n =3D pagevec_count(pvec); > for (i =3D 0; i < pagevec_count(pvec); i++) { for (i =3D 0; n; i++) { > struct page *page =3D pvec->pages[i]; > =20 > + if (!page) > + continue; > + > lruvec =3D relock_page_lruvec_irqsave(page, lruvec, &flags); > - __pagevec_lru_add_fn(page, lruvec); n--; > + > + for (j =3D i; j < pagevec_count(pvec); j++) { > + if (page_to_nid(pvec->pages[j]) !=3D page_to_nid(page) || > + page_memcg(pvec->pages[j]) !=3D page_memcg(page)) > + continue; > + > + __pagevec_lru_add_fn(pvec->pages[j], lruvec); > + pvec->pages[j] =3D NULL; n--; > + } > } > if (lruvec) > unlock_page_lruvec_irqrestore(lruvec, flags); >=20