From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id 96AFB6B0005 for ; Tue, 26 Apr 2016 15:40:49 -0400 (EDT) Received: by mail-lf0-f72.google.com with SMTP id j8so19766278lfd.0 for ; Tue, 26 Apr 2016 12:40:49 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id en8si250154wjd.165.2016.04.26.12.40.48 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 26 Apr 2016 12:40:48 -0700 (PDT) Subject: Re: [PATCH mmotm 3/3] mm, compaction: prevent nr_isolated_* from going negative References: <1461591269-28615-1-git-send-email-vbabka@suse.cz> <1461591350-28700-1-git-send-email-vbabka@suse.cz> <1461591350-28700-4-git-send-email-vbabka@suse.cz> <20160426005503.GC2707@js1304-P5Q-DELUXE> From: Vlastimil Babka Message-ID: <571FC43D.6010102@suse.cz> Date: Tue, 26 Apr 2016 21:40:45 +0200 MIME-Version: 1.0 In-Reply-To: <20160426005503.GC2707@js1304-P5Q-DELUXE> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Hugh Dickins , Rik van Riel On 04/26/2016 02:55 AM, Joonsoo Kim wrote: > On Mon, Apr 25, 2016 at 03:35:50PM +0200, Vlastimil Babka wrote: >> @@ -846,9 +845,11 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, >> spin_unlock_irqrestore(&zone->lru_lock, flags); >> locked = false; >> } >> - putback_movable_pages(migratelist); >> - nr_isolated = 0; >> + acct_isolated(zone, cc); >> + putback_movable_pages(&cc->migratepages); >> + cc->nr_migratepages = 0; >> cc->last_migrated_pfn = 0; >> + nr_isolated = 0; > > Is it better to use separate list and merge it cc->migratepages when > finishing instead of using cc->migratepages directly? If > isolate_migratepages() try to isolate more than one page block and keep > isolated page on previous pageblock, this putback all will invalidate > all the previous work. It would be beyond of the scope of this > function. Now, isolate_migratepages() try to isolate the page in one > pageblock so this code is safe. But, I think that removing such > dependency will be helpful in the future. I'm not strongly insisting it > so if you think it's not useful thing, please ignore this comment. migratelist was merely a reference to cc->migratepages, so it wouldn't prevent the situation you are suggesting. A truly separate list would need to be appended to cc->migratepages when leaving isolate_migratepages_block() and there's no need to do that right now. BTW, can you check patch 1/3? Thanks! Vlastimil > Thanks. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org