From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752212AbaEHFaK (ORCPT ); Thu, 8 May 2014 01:30:10 -0400 Received: from mail-pd0-f180.google.com ([209.85.192.180]:34138 "EHLO mail-pd0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750704AbaEHFaH (ORCPT ); Thu, 8 May 2014 01:30:07 -0400 Date: Wed, 7 May 2014 22:30:05 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Mel Gorman , Rik van Riel , Vlastimil Babka , Joonsoo Kim , Greg Thelen , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [patch -mm] mm, thp: avoid excessive compaction latency during fault fix In-Reply-To: Message-ID: References: User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org mm-thp-avoid-excessive-compaction-latency-during-fault.patch excludes sync compaction for all high order allocations other than thp. What we really want to do is suppress sync compaction for thp, but only during the page fault path. Orders greater than PAGE_ALLOC_COSTLY_ORDER aren't necessarily going to loop again so this is the only way to exhaust our capabilities before declaring that we can't allocate. Reported-by: Hugh Dickins Signed-off-by: David Rientjes --- mm/page_alloc.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2585,16 +2585,13 @@ rebalance: if (page) goto got_pg; - if (gfp_mask & __GFP_NO_KSWAPD) { - /* - * Khugepaged is allowed to try MIGRATE_SYNC_LIGHT, the latency - * of this allocation isn't critical. Everything else, however, - * should only be allowed to do MIGRATE_ASYNC to avoid excessive - * stalls during fault. - */ - if ((current->flags & (PF_KTHREAD | PF_KSWAPD)) == PF_KTHREAD) - migration_mode = MIGRATE_SYNC_LIGHT; - } + /* + * It can become very expensive to allocate transparent hugepages at + * fault, so use asynchronous memory compaction for THP unless it is + * khugepaged trying to collapse. + */ + if (!(gfp_mask & __GFP_NO_KSWAPD) || (current->flags & PF_KTHREAD)) + migration_mode = MIGRATE_SYNC_LIGHT; /* * If compaction is deferred for high-order allocations, it is because