From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id AB6866B006A for ; Wed, 13 Jan 2010 18:28:26 -0500 (EST) Received: from spaceape24.eur.corp.google.com (spaceape24.eur.corp.google.com [172.28.16.76]) by smtp-out.google.com with ESMTP id o0DNSMVu008251 for ; Wed, 13 Jan 2010 23:28:22 GMT Received: from pzk9 (pzk9.prod.google.com [10.243.19.137]) by spaceape24.eur.corp.google.com with ESMTP id o0DNRI3j010482 for ; Wed, 13 Jan 2010 15:28:21 -0800 Received: by pzk9 with SMTP id 9so5384874pzk.16 for ; Wed, 13 Jan 2010 15:28:21 -0800 (PST) Date: Wed, 13 Jan 2010 15:28:16 -0800 (PST) From: David Rientjes Subject: Re: [PATCH 7/7] Do not compact within a preferred zone after a compaction failure In-Reply-To: <1262795169-9095-8-git-send-email-mel@csn.ul.ie> Message-ID: References: <1262795169-9095-1-git-send-email-mel@csn.ul.ie> <1262795169-9095-8-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrea Arcangeli , Christoph Lameter , Adam Litke , Avi Kivity , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wed, 6 Jan 2010, Mel Gorman wrote: > The fragmentation index may indicate that a failure it due to external > fragmentation, a compaction run complete and an allocation failure still > fail. There are two obvious reasons as to why > > o Page migration cannot move all pages so fragmentation remains > o A suitable page may exist but watermarks are not met > > In the event of compaction and allocation failure, this patch prevents > compaction happening for a short interval. It's only recorded on the > preferred zone but that should be enough coverage. This could have been > implemented similar to the zonelist_cache but the increased size of the > zonelist did not appear to be justified. > > Signed-off-by: Mel Gorman > --- > include/linux/mmzone.h | 7 +++++++ > mm/page_alloc.c | 15 ++++++++++++++- > 2 files changed, 21 insertions(+), 1 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 30fe668..1d6ccbe 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -328,6 +328,13 @@ struct zone { > unsigned long *pageblock_flags; > #endif /* CONFIG_SPARSEMEM */ > > +#ifdef CONFIG_MIGRATION > + /* > + * If a compaction fails, do not try compaction again until > + * jiffies is after the value of compact_resume > + */ > + unsigned long compact_resume; > +#endif CONFIG_COMPACTION? > > ZONE_PADDING(_pad1_) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7275afb..9c86606 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1729,7 +1729,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, > cond_resched(); > > /* Try memory compaction for high-order allocations before reclaim */ > - if (order) { > + if (order && time_after(jiffies, preferred_zone->compact_resume)) { > *did_some_progress = try_to_compact_pages(zonelist, > order, gfp_mask, nodemask); > if (*did_some_progress != COMPACT_INCOMPLETE) { > @@ -1748,6 +1748,19 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, > * but not enough to satisfy watermarks. > */ > count_vm_event(COMPACTFAIL); > + > + /* > + * On failure, avoid compaction for a short time. > + * XXX: This is very unsatisfactory. The failure > + * to compact has nothing to do with time > + * and everything to do with the requested > + * order, the number of free pages and > + * watermarks. How to wait on that is more > + * unclear, but the answer would apply to > + * other areas where the VM waits based on > + * time. > + */ > + preferred_zone->compact_resume = jiffies + HZ/50; > } > } > This will need to be moved to (another) inline function dependent on CONFIG_COMPACTION since we don't have zone->compact_resume without it; it's probably better to seperate the function out rather than add #ifdef's within __alloc_pages_direct_reclaim(). -- 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