Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751906AbaBBFqc (ORCPT ); Sun, 2 Feb 2014 00:46:32 -0500 Received: from mail-pa0-f50.google.com ([209.85.220.50]:40298 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751806AbaBBFq3 (ORCPT ); Sun, 2 Feb 2014 00:46:29 -0500 Date: Sat, 1 Feb 2014 21:46:26 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton cc: Mel Gorman , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [patch] mm, compaction: avoid isolating pinned pages Message-ID: 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 Page migration will fail for memory that is pinned in memory with, for example, get_user_pages(). In this case, it is unnecessary to take zone->lru_lock or isolating the page and passing it to page migration which will ultimately fail. This is a racy check, the page can still change from under us, but in that case we'll just fail later when attempting to move the page. This avoids very expensive memory compaction when faulting transparent hugepages after pinning a lot of memory with a Mellanox driver. On a 128GB machine and pinning ~120GB of memory, before this patch we see the enormous disparity in the number of page migration failures because of the pinning (from /proc/vmstat): compact_blocks_moved 7609 compact_pages_moved 3431 compact_pagemigrate_failed 133219 compact_stall 13 After the patch, it is much more efficient: compact_blocks_moved 7998 compact_pages_moved 6403 compact_pagemigrate_failed 3 compact_stall 15 Signed-off-by: David Rientjes --- mm/compaction.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/compaction.c b/mm/compaction.c --- a/mm/compaction.c +++ b/mm/compaction.c @@ -578,6 +578,14 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc, continue; } + /* + * Migration will fail if an anonymous page is pinned in memory, + * so avoid taking zone->lru_lock and isolating it unnecessarily + * in an admittedly racy check. + */ + if (!page_mapping(page) && page_count(page)) + continue; + /* Check if it is ok to still hold the lock */ locked = compact_checklock_irqsave(&zone->lru_lock, &flags, locked, cc); -- 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/