From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f47.google.com (mail-qg0-f47.google.com [209.85.192.47]) by kanga.kvack.org (Postfix) with ESMTP id B35736B0035 for ; Mon, 12 May 2014 11:34:38 -0400 (EDT) Received: by mail-qg0-f47.google.com with SMTP id j107so7907879qga.34 for ; Mon, 12 May 2014 08:34:38 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTP id o1si6179419qai.31.2014.05.12.08.34.37 for ; Mon, 12 May 2014 08:34:38 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH] mm, compaction: properly signal and act upon lock and need_sched() contention Date: Mon, 12 May 2014 11:34:11 -0400 Message-Id: <5370ea0e.c142e00a.577f.ffffe885SMTPIN_ADDED_BROKEN@mx.google.com> In-Reply-To: <1399904111-23520-1-git-send-email-vbabka@suse.cz> References: <20140508051747.GA9161@js1304-P5Q-DELUXE> <1399904111-23520-1-git-send-email-vbabka@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Joonsoo Kim , Andrew Morton , David Rientjes , Hugh Dickins , Greg Thelen , linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, Mel Gorman , b.zolnierkie@samsung.com, mina86@mina86.com, cl@linux.com, Rik van Riel On Mon, May 12, 2014 at 04:15:11PM +0200, Vlastimil Babka wrote: > Compaction uses compact_checklock_irqsave() function to periodically check for > lock contention and need_resched() to either abort async compaction, or to > free the lock, schedule and retake the lock. When aborting, cc->contended is > set to signal the contended state to the caller. Two problems have been > identified in this mechanism. > > First, compaction also calls directly cond_resched() in both scanners when no > lock is yet taken. This call either does not abort async compaction, or set > cc->contended appropriately. This patch introduces a new > compact_check_resched() function to achieve both. > > Second, isolate_freepages() does not check if isolate_freepages_block() > aborted due to contention, and advances to the next pageblock. This violates > the principle of aborting on contention, and might result in pageblocks not > being scanned completely, since the scanning cursor is advanced. This patch > makes isolate_freepages_block() check the cc->contended flag and abort. > > Reported-by: Joonsoo Kim > Signed-off-by: Vlastimil Babka > Cc: Minchan Kim > Cc: Mel Gorman > Cc: Bartlomiej Zolnierkiewicz > Cc: Michal Nazarewicz > Cc: Naoya Horiguchi > Cc: Christoph Lameter > Cc: Rik van Riel > --- > mm/compaction.c | 40 +++++++++++++++++++++++++++++++++------- > 1 file changed, 33 insertions(+), 7 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 83ca6f9..b34ab7c 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -222,6 +222,27 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags, > return true; > } > > +/* > + * Similar to compact_checklock_irqsave() (see its comment) for places where > + * a zone lock is not concerned. > + * > + * Returns false when compaction should abort. > + */ > +static inline bool compact_check_resched(struct compact_control *cc) > +{ > + /* async compaction aborts if contended */ > + if (need_resched()) { > + if (cc->mode == MIGRATE_ASYNC) { > + cc->contended = true; This changes the meaning of contended in struct compact_control (not just indicating lock contention,) so please update the comment in mm/internal.h too. Reviewed-by: Naoya Horiguchi Thanks, Naoya Horiguchi -- 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