Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757015Ab1FGPuj (ORCPT ); Tue, 7 Jun 2011 11:50:39 -0400 Received: from mail-pw0-f46.google.com ([209.85.160.46]:56366 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756985Ab1FGPug (ORCPT ); Tue, 7 Jun 2011 11:50:36 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=agDYWZnTCzKSEpDgqszfYF5lre6NkFnnxx+vbeKQsM15lsRaCOcmB9PbrDip+hQ68E RkCsvElM/d+E9GK7i1BEfz0Wp5/ylRtCzQzhbtSbK5qAlzcxFKsdPnWX19L2PFKjAgG2 8OWFfNfoK+NV1HrhiAH0Zcih/igylCaQRHlhA= Date: Wed, 8 Jun 2011 00:50:29 +0900 From: Minchan Kim To: Mel Gorman Cc: Andrew Morton , Andrea Arcangeli , Thomas Sattler , Ury Stankevich , Andi Kleen , linux-mm , linux-kernel Subject: Re: [PATCH 4/4] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous Message-ID: <20110607155029.GL1686@barrios-laptop> References: <1307459225-4481-1-git-send-email-mgorman@suse.de> <1307459225-4481-5-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1307459225-4481-5-git-send-email-mgorman@suse.de> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3682 Lines: 97 On Tue, Jun 07, 2011 at 04:07:05PM +0100, Mel Gorman wrote: > Asynchronous compaction is used when promoting to huge pages. This is > all very nice but if there are a number of processes in compacting > memory, a large number of pages can be isolated. An "asynchronous" > process can stall for long periods of time as a result with a user > reporting that firefox can stall for 10s of seconds. This patch aborts > asynchronous compaction if too many pages are isolated as it's better to > fail a hugepage promotion than stall a process. > > Reported-and-tested-by: Ury Stankevich > Signed-off-by: Mel Gorman > --- > mm/compaction.c | 28 +++++++++++++++++++++++----- > 1 files changed, 23 insertions(+), 5 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 5c744ab..cb28580 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -251,11 +251,18 @@ static bool too_many_isolated(struct zone *zone) > return isolated > (inactive + active) / 2; > } > > +/* possible outcome of isolate_migratepages */ > +typedef enum { > + ISOLATE_ABORT, /* Abort compaction now */ > + ISOLATE_NONE, /* No pages isolated, continue scanning */ > + ISOLATE_SUCCESS, /* Pages isolated, migrate */ > +} isolate_migrate_t; > + > /* > * Isolate all pages that can be migrated from the block pointed to by > * the migrate scanner within compact_control. > */ > -static unsigned long isolate_migratepages(struct zone *zone, > +static isolate_migrate_t isolate_migratepages(struct zone *zone, > struct compact_control *cc) > { > unsigned long low_pfn, end_pfn; > @@ -272,7 +279,7 @@ static unsigned long isolate_migratepages(struct zone *zone, > /* Do not cross the free scanner or scan within a memory hole */ > if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) { > cc->migrate_pfn = end_pfn; > - return 0; > + return ISOLATE_NONE; > } > > /* > @@ -281,10 +288,14 @@ static unsigned long isolate_migratepages(struct zone *zone, > * delay for some time until fewer pages are isolated > */ > while (unlikely(too_many_isolated(zone))) { > + /* async migration should just abort */ > + if (!cc->sync) > + return ISOLATE_ABORT; > + > congestion_wait(BLK_RW_ASYNC, HZ/10); > > if (fatal_signal_pending(current)) > - return 0; > + return ISOLATE_ABORT; > } > > /* Time to isolate some pages for migration */ > @@ -369,7 +380,7 @@ static unsigned long isolate_migratepages(struct zone *zone, > > trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); > > - return cc->nr_migratepages; > + return ISOLATE_SUCCESS; > } > > /* > @@ -533,8 +544,14 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) > unsigned long nr_migrate, nr_remaining; > int err; > > - if (!isolate_migratepages(zone, cc)) > + switch (isolate_migratepages(zone, cc)) { > + case ISOLATE_ABORT: In this case, you change old behavior slightly. In old case, we return COMPACT_PARTIAL to cancel migration. But this patch makes to return COMPACT_SUCCESS. At present, return value of compact_zone is only used by __alloc_pages_direct_compact and it only consider COMPACT_SKIPPED so it would be not a problem. But I think it would be better to return COMPACT_PARTIAL instead of COMPACT_CONTINUE for consistency with compact_finished and right semantic for the future user of compact_zone. -- Kind regards Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/