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=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT 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 27456C433E1 for ; Sun, 16 Aug 2020 03:48:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DC4412065C for ; Sun, 16 Aug 2020 03:48:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DC4412065C 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 8B2316B0005; Sat, 15 Aug 2020 23:48:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 862556B0007; Sat, 15 Aug 2020 23:48:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 79E2B6B0008; Sat, 15 Aug 2020 23:48:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0221.hostedemail.com [216.40.44.221]) by kanga.kvack.org (Postfix) with ESMTP id 61D1F6B0005 for ; Sat, 15 Aug 2020 23:48:27 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 27042180AD80F for ; Sun, 16 Aug 2020 03:48:27 +0000 (UTC) X-FDA: 77155049454.28.root66_4101fad2700a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin28.hostedemail.com (Postfix) with ESMTP id E3C656C29 for ; Sun, 16 Aug 2020 03:48:26 +0000 (UTC) X-HE-Tag: root66_4101fad2700a X-Filterd-Recvd-Size: 2893 Received: from out30-43.freemail.mail.aliyun.com (out30-43.freemail.mail.aliyun.com [115.124.30.43]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Sun, 16 Aug 2020 03:48:22 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04427;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0U5s0mT9_1597549686; Received: from aliy80.localdomain(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U5s0mT9_1597549686) by smtp.aliyun-inc.com(127.0.0.1); Sun, 16 Aug 2020 11:48:11 +0800 From: Alex Shi To: Cc: Andrew Morton , Hugh Dickins , Alexander Duyck , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 2/2] mm/pageblock: remove false sharing in pageblock_flags Date: Sun, 16 Aug 2020 11:47:57 +0800 Message-Id: <1597549677-7480-2-git-send-email-alex.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1597549677-7480-1-git-send-email-alex.shi@linux.alibaba.com> References: <1597549677-7480-1-git-send-email-alex.shi@linux.alibaba.com> X-Rspamd-Queue-Id: E3C656C29 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: Current pageblock_flags is only 4 bits, so it has to share a char size in cmpxchg when get set, the false sharing cause perf drop. If we incrase the bits up to 8, false sharing would gone in cmpxchg. and the only cost is half char per pageblock, which is half char per 128MB on x86, 4 chars in 1 GB. Signed-off-by: Alex Shi Cc: Andrew Morton Cc: Hugh Dickins Cc: Alexander Duyck Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org --- include/linux/pageblock-flags.h | 2 +- mm/page_alloc.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h index d189441568eb..556fc2c0b392 100644 --- a/include/linux/pageblock-flags.h +++ b/include/linux/pageblock-flags.h @@ -25,7 +25,7 @@ enum pageblock_bits { * Assume the bits will always align on a word. If this assumption * changes then get/set pageblock needs updating. */ - NR_PAGEBLOCK_BITS + NR_PAGEBLOCK_BITS = 8 }; #ifdef CONFIG_HUGETLB_PAGE diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 142803d1f49b..01c3fb822732 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -521,7 +521,7 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags, unsigned long bitidx, word_bitidx; unsigned char old_word, word; - BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4); + BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 8); BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); bitmap = get_pageblock_bitmap(page, pfn); -- 1.8.3.1