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=-12.7 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=unavailable 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 CC1EEC433E1 for ; Wed, 19 Aug 2020 05:48:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 06F4A20772 for ; Wed, 19 Aug 2020 05:48:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 06F4A20772 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 2D02F8D000A; Wed, 19 Aug 2020 01:48:35 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 281508D0002; Wed, 19 Aug 2020 01:48:35 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1989D8D000A; Wed, 19 Aug 2020 01:48:35 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0242.hostedemail.com [216.40.44.242]) by kanga.kvack.org (Postfix) with ESMTP id F40BA8D0002 for ; Wed, 19 Aug 2020 01:48:34 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id A9A26181AEF0B for ; Wed, 19 Aug 2020 05:48:34 +0000 (UTC) X-FDA: 77166238548.15.song60_6313a3d27025 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id 7B0851814B0C1 for ; Wed, 19 Aug 2020 05:48:34 +0000 (UTC) X-HE-Tag: song60_6313a3d27025 X-Filterd-Recvd-Size: 3002 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Wed, 19 Aug 2020 05:48:32 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04357;MF=alex.shi@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0U6CFft4_1597816103; Received: from aliy80.localdomain(mailfrom:alex.shi@linux.alibaba.com fp:SMTPD_---0U6CFft4_1597816103) by smtp.aliyun-inc.com(127.0.0.1); Wed, 19 Aug 2020 13:48:24 +0800 From: Alex Shi To: Matthew Wilcox , David Hildenbrand Cc: Andrew Morton , Hugh Dickins , Alexander Duyck , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 2/2] mm/pageblock: remove false sharing in pageblock_flags Date: Wed, 19 Aug 2020 13:47:55 +0800 Message-Id: <1597816075-61091-2-git-send-email-alex.shi@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1597816075-61091-1-git-send-email-alex.shi@linux.alibaba.com> References: <1597816075-61091-1-git-send-email-alex.shi@linux.alibaba.com> X-Rspamd-Queue-Id: 7B0851814B0C1 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..f785c9d6d68c 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 = BITS_PER_BYTE }; #ifdef CONFIG_HUGETLB_PAGE diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f60071e8a4e1..65f692c762d5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -517,7 +517,7 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags, unsigned long bitidx, byte_bitidx; unsigned char old_byte, byte; - BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4); + BUILD_BUG_ON(NR_PAGEBLOCK_BITS != BITS_PER_BYTE); BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits)); bitmap = get_pageblock_bitmap(page, pfn); -- 1.8.3.1