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=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 EE99CC433E3 for ; Tue, 23 Jun 2020 12:42:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C9C6E20738 for ; Tue, 23 Jun 2020 12:42:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732669AbgFWMmS (ORCPT ); Tue, 23 Jun 2020 08:42:18 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:35067 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732589AbgFWMmR (ORCPT ); Tue, 23 Jun 2020 08:42:17 -0400 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=e01e07488;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0U0WDmIY_1592916132; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U0WDmIY_1592916132) by smtp.aliyun-inc.com(127.0.0.1); Tue, 23 Jun 2020 20:42:12 +0800 From: Wei Yang To: mgorman@suse.de, akpm@linux-foundation.org, richard.weiyang@linux.alibaba.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/4] mm/page_alloc.c: simplify pageblock bitmap access Date: Tue, 23 Jun 2020 20:42:00 +0800 Message-Id: <20200623124201.8199-3-richard.weiyang@linux.alibaba.com> X-Mailer: git-send-email 2.20.1 (Apple Git-117) In-Reply-To: <20200623124201.8199-1-richard.weiyang@linux.alibaba.com> References: <20200623124201.8199-1-richard.weiyang@linux.alibaba.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >From commit e58469bafd05 ("mm: page_alloc: use word-based accesses for get/set pageblock bitmaps"), pageblock bitmap is accessed with word-based access. This operation could be simplified a little. Intuitively, if we want to get a bit range [start_idx, end_idx] in a word, we can do like this: mask = (1 << (end_bitidx - start_bitidx + 1)) - 1; ret = (word >> start_idx) & mask; And also if we want to set a bit range [start_idx, end_idx] with flags, we can do the same by just shift start_bitidx. By doing so we reduce some instructions for these two helper functions: Before Patched set_pfnblock_flags_mask 209 198(-5%) get_pfnblock_flags_mask 101 87(-13%) Since the syntax is changed a little, we need to check the whole 4-bit migrate_type instead of part of it. CC: Mel Gorman Signed-off-by: Wei Yang --- include/linux/pageblock-flags.h | 22 +++++++--------------- mm/page_alloc.c | 13 ++++++------- 2 files changed, 13 insertions(+), 22 deletions(-) diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h index c066fec5b74b..6556e4474409 100644 --- a/include/linux/pageblock-flags.h +++ b/include/linux/pageblock-flags.h @@ -66,25 +66,17 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long mask); /* Declarations for getting and setting flags. See mm/page_alloc.c */ -#define get_pageblock_flags_group(page, start_bitidx, end_bitidx) \ - get_pfnblock_flags_mask(page, page_to_pfn(page), \ - end_bitidx, \ - (1 << (end_bitidx - start_bitidx + 1)) - 1) -#define set_pageblock_flags_group(page, flags, start_bitidx, end_bitidx) \ - set_pfnblock_flags_mask(page, flags, page_to_pfn(page), \ - end_bitidx, \ - (1 << (end_bitidx - start_bitidx + 1)) - 1) - #ifdef CONFIG_COMPACTION #define get_pageblock_skip(page) \ - get_pageblock_flags_group(page, PB_migrate_skip, \ - PB_migrate_skip) + get_pfnblock_flags_mask(page, page_to_pfn(page), \ + PB_migrate_skip, (1 << (PB_migrate_skip))) #define clear_pageblock_skip(page) \ - set_pageblock_flags_group(page, 0, PB_migrate_skip, \ - PB_migrate_skip) + set_pfnblock_flags_mask(page, 0, page_to_pfn(page), \ + PB_migrate_skip, (1 << PB_migrate_skip)) #define set_pageblock_skip(page) \ - set_pageblock_flags_group(page, 1, PB_migrate_skip, \ - PB_migrate_skip) + set_pfnblock_flags_mask(page, (1 << PB_migrate_skip), \ + page_to_pfn(page), \ + PB_migrate_skip, (1 << PB_migrate_skip)) #else static inline bool get_pageblock_skip(struct page *page) { diff --git a/mm/page_alloc.c b/mm/page_alloc.c index efc2c355ac52..9da416eec284 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -489,8 +489,7 @@ static __always_inline unsigned long __get_pfnblock_flags_mask(struct page *page bitidx &= (BITS_PER_LONG-1); word = bitmap[word_bitidx]; - bitidx += end_bitidx; - return (word >> (BITS_PER_LONG - bitidx - 1)) & mask; + return (word >> bitidx) & mask; } unsigned long get_pfnblock_flags_mask(struct page *page, unsigned long pfn, @@ -532,9 +531,8 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags, VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); - bitidx += end_bitidx; - mask <<= (BITS_PER_LONG - bitidx - 1); - flags <<= (BITS_PER_LONG - bitidx - 1); + mask <<= bitidx; + flags <<= bitidx; word = READ_ONCE(bitmap[word_bitidx]); for (;;) { @@ -551,8 +549,9 @@ void set_pageblock_migratetype(struct page *page, int migratetype) migratetype < MIGRATE_PCPTYPES)) migratetype = MIGRATE_UNMOVABLE; - set_pageblock_flags_group(page, (unsigned long)migratetype, - PB_migrate, PB_migrate_end); + set_pfnblock_flags_mask(page, (unsigned long)migratetype, + page_to_pfn(page), PB_migrate_end, + MIGRATETYPE_MASK); } #ifdef CONFIG_DEBUG_VM -- 2.20.1 (Apple Git-117)