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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 0C775C433DB for ; Wed, 24 Feb 2021 20:09:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7B6DD64F08 for ; Wed, 24 Feb 2021 20:09:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B6DD64F08 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 08F4A8D0055; Wed, 24 Feb 2021 15:09:39 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 03EAC8D001E; Wed, 24 Feb 2021 15:09:38 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E95FB8D0055; Wed, 24 Feb 2021 15:09:38 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0239.hostedemail.com [216.40.44.239]) by kanga.kvack.org (Postfix) with ESMTP id D2DB68D001E for ; Wed, 24 Feb 2021 15:09:38 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 9D5D682F4072 for ; Wed, 24 Feb 2021 20:09:38 +0000 (UTC) X-FDA: 77854251636.06.0452A71 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf20.hostedemail.com (Postfix) with ESMTP id EDFD92BCF for ; Wed, 24 Feb 2021 20:09:37 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id A66E764F0D; Wed, 24 Feb 2021 20:09:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614197377; bh=GSGlVlt9tDAHnmijpnHpxdcRPGZZnZy58WjHF9y9VNI=; h=Date:From:To:Subject:In-Reply-To:From; b=SDEZ1twNEaYS6NogeeNPgZqZge62MhcWJ/hDELpr9axCCQwenUFbMo3B5QSLGk0MK 1NZupWLqsabKUq4ARTBREVrXqqnRTNZw0M81/dxdDGtElyIciQY2WOLKf7+dw1fiVa r3+vG7n4jW9Agh0mPY4jJqB6CbcE6WhVkWlBUEjM= Date: Wed, 24 Feb 2021 12:09:36 -0800 From: Andrew Morton To: akpm@linux-foundation.org, linux-mm@kvack.org, mgorman@techsingularity.net, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz, vvghjk1234@gmail.com Subject: [patch 158/173] mm/compaction: fix misbehaviors of fast_find_migrateblock() Message-ID: <20210224200936.2tiDMI299%akpm@linux-foundation.org> In-Reply-To: <20210224115824.1e289a6895087f10c41dd8d6@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EDFD92BCF X-Stat-Signature: gjibriifgeb3xy5ufjra55uo9euuexso Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf20; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614197377-246320 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: From: Wonhyuk Yang Subject: mm/compaction: fix misbehaviors of fast_find_migrateblock() In the fast_find_migrateblock(), it iterates ocer the freelist to find the proper pageblock. But there are some misbehaviors. First, if the page we found is equal to cc->migrate_pfn, it is considered that we didn't find a suitable pageblock. Secondly, if the loop was terminated because order is less than PAGE_ALLOC_COSTLY_ORDER, it could be considered that we found a suitable one. Thirdly, if the skip bit is set on the page block and we goto continue, it doesn't check nr_scanned. Fourthly, if the page block's skip bit is set, it checks that page block is the last of list, which is unnecessary. Link: https://lkml.kernel.org/r/20210128130411.6125-1-vvghjk1234@gmail.com Fixes: 70b44595eafe9 ("mm, compaction: use free lists to quickly locate a migration source") Signed-off-by: Wonhyuk Yang Acked-by: Vlastimil Babka Cc: Mel Gorman Signed-off-by: Andrew Morton --- mm/compaction.c | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-) --- a/mm/compaction.c~mm-compactoin-fix-misbehaviors-of-fast_find_migrateblock +++ a/mm/compaction.c @@ -1698,6 +1698,7 @@ static unsigned long fast_find_migratebl unsigned long pfn = cc->migrate_pfn; unsigned long high_pfn; int order; + bool found_block = false; /* Skip hints are relied on to avoid repeats on the fast search */ if (cc->ignore_skip_hint) @@ -1740,7 +1741,7 @@ static unsigned long fast_find_migratebl high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance); for (order = cc->order - 1; - order >= PAGE_ALLOC_COSTLY_ORDER && pfn == cc->migrate_pfn && nr_scanned < limit; + order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit; order--) { struct free_area *area = &cc->zone->free_area[order]; struct list_head *freelist; @@ -1755,7 +1756,11 @@ static unsigned long fast_find_migratebl list_for_each_entry(freepage, freelist, lru) { unsigned long free_pfn; - nr_scanned++; + if (nr_scanned++ >= limit) { + move_freelist_tail(freelist, freepage); + break; + } + free_pfn = page_to_pfn(freepage); if (free_pfn < high_pfn) { /* @@ -1764,12 +1769,8 @@ static unsigned long fast_find_migratebl * the list assumes an entry is deleted, not * reordered. */ - if (get_pageblock_skip(freepage)) { - if (list_is_last(freelist, &freepage->lru)) - break; - + if (get_pageblock_skip(freepage)) continue; - } /* Reorder to so a future search skips recent pages */ move_freelist_tail(freelist, freepage); @@ -1777,15 +1778,10 @@ static unsigned long fast_find_migratebl update_fast_start_pfn(cc, free_pfn); pfn = pageblock_start_pfn(free_pfn); cc->fast_search_fail = 0; + found_block = true; set_pageblock_skip(freepage); break; } - - if (nr_scanned >= limit) { - cc->fast_search_fail++; - move_freelist_tail(freelist, freepage); - break; - } } spin_unlock_irqrestore(&cc->zone->lock, flags); } @@ -1796,9 +1792,10 @@ static unsigned long fast_find_migratebl * If fast scanning failed then use a cached entry for a page block * that had free pages as the basis for starting a linear scan. */ - if (pfn == cc->migrate_pfn) + if (!found_block) { + cc->fast_search_fail++; pfn = reinit_migrate_pfn(cc); - + } return pfn; } _