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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 9D6B4C433FE for ; Fri, 4 Dec 2020 15:28:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 22B4322B43 for ; Fri, 4 Dec 2020 15:28:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 22B4322B43 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 478B86B006E; Fri, 4 Dec 2020 10:28:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 428646B0070; Fri, 4 Dec 2020 10:28:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 33E956B0071; Fri, 4 Dec 2020 10:28:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0035.hostedemail.com [216.40.44.35]) by kanga.kvack.org (Postfix) with ESMTP id 156426B006E for ; Fri, 4 Dec 2020 10:28:43 -0500 (EST) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id C284A1F06 for ; Fri, 4 Dec 2020 15:28:42 +0000 (UTC) X-FDA: 77555982084.18.mark09_1003f2d273c5 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id 9DEE8100ED0CB for ; Fri, 4 Dec 2020 15:28:42 +0000 (UTC) X-HE-Tag: mark09_1003f2d273c5 X-Filterd-Recvd-Size: 3679 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Dec 2020 15:28:41 +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 904DDACA8; Fri, 4 Dec 2020 15:28:40 +0000 (UTC) To: Muchun Song , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20201204125640.51804-1-songmuchun@bytedance.com> From: Vlastimil Babka Subject: Re: [PATCH v2] mm/page_alloc: speeding up the iteration of max_order Message-ID: <27277a9f-c726-b033-51c1-d88f978fabfd@suse.cz> Date: Fri, 4 Dec 2020 16:28:40 +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: <20201204125640.51804-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=utf-8 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 12/4/20 1:56 PM, Muchun Song wrote: > When we free a page whose order is very close to MAX_ORDER and greater > than pageblock_order, it wastes some CPU cycles to increase max_order > to MAX_ORDER one by one and check the pageblock migratetype of that pag= e > repeatedly especially when MAX_ORDER is much larger than pageblock_orde= r. I would add: We also should not be checking migratetype of buddy when "order =3D=3D MA= X_ORDER - 1" as the buddy pfn may be invalid, so adjust the condition. With the new= check, we don't need the max_order check anymore, so we replace it. Also adjust max_order initialization so that it's lower by one than previ= ously, which makes the code hopefully more clear. > Signed-off-by: Muchun Song Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and= other pageblocks") Acked-by: Vlastimil Babka Thanks! > --- > Changes in v2: > - Rework the code suggested by Vlastimil. Thanks. >=20 > mm/page_alloc.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) >=20 > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index f91df593bf71..56e603eea1dd 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1002,7 +1002,7 @@ static inline void __free_one_page(struct page *p= age, > struct page *buddy; > bool to_tail; > =20 > - max_order =3D min_t(unsigned int, MAX_ORDER, pageblock_order + 1); > + max_order =3D min_t(unsigned int, MAX_ORDER - 1, pageblock_order); > =20 > VM_BUG_ON(!zone_is_initialized(zone)); > VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP, page); > @@ -1015,7 +1015,7 @@ static inline void __free_one_page(struct page *p= age, > VM_BUG_ON_PAGE(bad_range(zone, page), page); > =20 > continue_merging: > - while (order < max_order - 1) { > + while (order < max_order) { > if (compaction_capture(capc, page, order, migratetype)) { > __mod_zone_freepage_state(zone, -(1 << order), > migratetype); > @@ -1041,7 +1041,7 @@ static inline void __free_one_page(struct page *p= age, > pfn =3D combined_pfn; > order++; > } > - if (max_order < MAX_ORDER) { > + if (order < MAX_ORDER - 1) { > /* If we are here, it means order is >=3D pageblock_order. > * We want to prevent merge between freepages on isolate > * pageblock and normal pageblock. Without this, pageblock > @@ -1062,7 +1062,7 @@ static inline void __free_one_page(struct page *p= age, > is_migrate_isolate(buddy_mt))) > goto done_merging; > } > - max_order++; > + max_order =3D order + 1; > goto continue_merging; > } > =20 >=20