From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756229Ab3KZK6V (ORCPT ); Tue, 26 Nov 2013 05:58:21 -0500 Received: from cantor2.suse.de ([195.135.220.15]:41009 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755283Ab3KZK6S (ORCPT ); Tue, 26 Nov 2013 05:58:18 -0500 Date: Tue, 26 Nov 2013 10:58:15 +0000 From: Mel Gorman To: Vlastimil Babka Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel Subject: Re: [PATCH 4/5] mm: compaction: do not mark unmovable pageblocks as skipped in async compaction Message-ID: <20131126105815.GI5285@suse.de> References: <1385389570-11393-1-git-send-email-vbabka@suse.cz> <1385389570-11393-5-git-send-email-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1385389570-11393-5-git-send-email-vbabka@suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 25, 2013 at 03:26:09PM +0100, Vlastimil Babka wrote: > Compaction temporarily marks pageblocks where it fails to isolate pages as > to-be-skipped in further compactions, in order to improve efficiency. One of > the reasons to fail isolating pages is that isolation is not attempted in > pageblocks that are not of MIGRATE_MOVABLE (or CMA) type. > > The problem is that blocks skipped due to not being MIGRATE_MOVABLE in async > compaction become skipped due to the temporary mark also in future sync > compaction. Moreover, this may follow quite soon during __alloc_page_slowpath, > without much time for kswapd to clear the pageblock skip marks. This goes > against the idea that sync compaction should try to scan these blocks more > thoroughly than the async compaction. > > The fix is to ensure in async compaction that these !MIGRATE_MOVABLE blocks are > not marked to be skipped. Note this should not affect performance or locking > impact of further async compactions, as skipping a block due to being > !MIGRATE_MOVABLE is done soon after skipping a block marked to be skipped, both > without locking. > > Cc: Mel Gorman > Cc: Rik van Riel > Signed-off-by: Vlastimil Babka > --- > mm/compaction.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 0702bdf..f481193 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -455,6 +455,8 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > unsigned long flags; > bool locked = false; > struct page *page = NULL, *valid_page = NULL; > + bool skipped_unmovable = false; > + > whitespace damage. > /* > * Ensure that there are not too many pages isolated from the LRU > @@ -530,6 +532,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, > if (!cc->sync && last_pageblock_nr != pageblock_nr && > !migrate_async_suitable(get_pageblock_migratetype(page))) { > cc->finished_update_migrate = true; > + skipped_unmovable = true; > goto next_pageblock; > } > Minor nitpick, but it's also unreclaimable and isolate blocks that are being skipped here. If you do another revision, consider rephrasing s/unmovable/unsuitable/ where appropriate. It's fairly obvious from context so if you decide not to, that's fine too. > @@ -624,7 +627,7 @@ next_pageblock: > spin_unlock_irqrestore(&zone->lru_lock, flags); > > /* Update the pageblock-skip if the whole pageblock was scanned */ > - if (low_pfn == end_pfn) > + if (low_pfn == end_pfn && !skipped_unmovable) > update_pageblock_skip(cc, valid_page, nr_isolated, true); > This comment is now out of date. If the comment gets updated then feel free to add Acked-by: Mel Gorman -- Mel Gorman SUSE Labs