Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756973Ab1E3NNI (ORCPT ); Mon, 30 May 2011 09:13:08 -0400 Received: from gir.skynet.ie ([193.1.99.77]:49135 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754585Ab1E3NNG (ORCPT ); Mon, 30 May 2011 09:13:06 -0400 Date: Mon, 30 May 2011 14:13:00 +0100 From: Mel Gorman To: akpm@linux-foundation.org Cc: Ury Stankevich , KOSAKI Motohiro , Andrea Arcangeli , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@kernel.org Subject: [PATCH] mm: compaction: Abort compaction if too many pages are isolated and caller is asynchronous Message-ID: <20110530131300.GQ5044@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline 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 Content-Length: 3762 Lines: 110 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. If accepted, this should also be considered for 2.6.39-stable. It should also be considered for 2.6.38-stable but ideally [11bc82d6: mm: compaction: Use async migration for __GFP_NO_KSWAPD and enforce no writeback] would be applied to 2.6.38 before consideration. Reported-and-Tested-by: Ury Stankevich Signed-off-by: Mel Gorman --- mm/compaction.c | 32 ++++++++++++++++++++++++++------ 1 files changed, 26 insertions(+), 6 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 021a296..331a2ee 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -240,11 +240,20 @@ 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. + * + * Returns false if compaction should abort at this point due to congestion. */ -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; @@ -261,7 +270,7 @@ 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; } /* @@ -270,10 +279,14 @@ 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 */ @@ -358,7 +371,7 @@ static unsigned long isolate_migratepages(struct zone *zone, trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); - return cc->nr_migratepages; + return ISOLATE_SUCCESS; } /* @@ -522,9 +535,15 @@ 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: + goto out; + case ISOLATE_NONE: continue; - + case ISOLATE_SUCCESS: + ; + } + nr_migrate = cc->nr_migratepages; err = migrate_pages(&cc->migratepages, compaction_alloc, (unsigned long)cc, false, @@ -547,6 +566,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) } +out: /* Release free pages and check accounting */ cc->nr_freepages -= release_freepages(&cc->freepages); VM_BUG_ON(cc->nr_freepages != 0); -- 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/