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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 99A1BC433E1 for ; Sun, 16 Aug 2020 04:09:18 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4A8772068E for ; Sun, 16 Aug 2020 04:09:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="n88tpd+3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4A8772068E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B1C266B0002; Sun, 16 Aug 2020 00:09:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id ACC846B0003; Sun, 16 Aug 2020 00:09:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9E2836B0005; Sun, 16 Aug 2020 00:09:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0219.hostedemail.com [216.40.44.219]) by kanga.kvack.org (Postfix) with ESMTP id 84D3B6B0002 for ; Sun, 16 Aug 2020 00:09:17 -0400 (EDT) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 42346824556B for ; Sun, 16 Aug 2020 04:09:17 +0000 (UTC) X-FDA: 77155101954.06.robin29_4d106952700b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin06.hostedemail.com (Postfix) with ESMTP id 0F6D81004560D for ; Sun, 16 Aug 2020 04:09:17 +0000 (UTC) X-HE-Tag: robin29_4d106952700b X-Filterd-Recvd-Size: 2354 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf43.hostedemail.com (Postfix) with ESMTP for ; Sun, 16 Aug 2020 04:09:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=+w7jWuDj+prWa0IEJcK+RwKnK1Y4vdCU//6WZuG/yR0=; b=n88tpd+3bXfovuKM3r7p8BYPUP CqVWIdLlaREhk0lIMsntjd4Q2OpO0FR5bKHA8lHcoxhCLCAdeM8+2qMogRlujRp+FkEpch3E3a02S o1t603FyW2VZAmGfurnoszG4rNGvFK8z2D6mC09a0MFGiENXzmPUse/8j52OTo0HmZSUqh7uc3Sj1 qeDq9W332dpXi+idfm75qkTe0YB6C/Vx3VfsBNmnRSFpBO68z6ZDgq/a8NjMfYNLfIcirlEMHuLmb ZMifEAFZZCcPzPIGbEYewonEmwQmOK9BAyZ8+kYOoQUm3WnRspaOlMSYNFxlMt25lH5sITZVL9EgI PzbQrkHw==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1k79yj-000195-9K; Sun, 16 Aug 2020 04:09:05 +0000 Date: Sun, 16 Aug 2020 05:09:05 +0100 From: Matthew Wilcox To: Alex Shi Cc: Andrew Morton , Hugh Dickins , Alexander Duyck , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags Message-ID: <20200816040905.GF17456@casper.infradead.org> References: <1597549677-7480-1-git-send-email-alex.shi@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1597549677-7480-1-git-send-email-alex.shi@linux.alibaba.com> X-Rspamd-Queue-Id: 0F6D81004560D 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: On Sun, Aug 16, 2020 at 11:47:56AM +0800, Alex Shi wrote: > +++ b/mm/page_alloc.c > @@ -467,6 +467,8 @@ static inline int pfn_to_bitidx(struct page *page, unsigned long pfn) > return (pfn >> pageblock_order) * NR_PAGEBLOCK_BITS; > } > > +#define BITS_PER_CHAR 8 include/linux/bits.h:#define BITS_PER_BYTE 8 > bitmap = get_pageblock_bitmap(page, pfn); > bitidx = pfn_to_bitidx(page, pfn); > - word_bitidx = bitidx / BITS_PER_LONG; > - bitidx &= (BITS_PER_LONG-1); > + word_bitidx = bitidx / BITS_PER_CHAR; > + bitidx &= (BITS_PER_CHAR-1); It's not a word any more. it's a byte.