Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757801AbZFIChv (ORCPT ); Mon, 8 Jun 2009 22:37:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752354AbZFICho (ORCPT ); Mon, 8 Jun 2009 22:37:44 -0400 Received: from mga14.intel.com ([143.182.124.37]:1225 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751938AbZFIChn (ORCPT ); Mon, 8 Jun 2009 22:37:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.41,328,1241420400"; d="scan'208";a="152078349" Date: Tue, 9 Jun 2009 10:37:31 +0800 From: Wu Fengguang To: Mel Gorman Cc: KOSAKI Motohiro , Rik van Riel , Christoph Lameter , "Zhang, Yanmin" , "linuxram@us.ibm.com" , linux-mm , LKML Subject: Re: [PATCH 2/3] Properly account for the number of page cache pages zone_reclaim() can reclaim Message-ID: <20090609023731.GA7875@localhost> References: <1244466090-10711-1-git-send-email-mel@csn.ul.ie> <1244466090-10711-3-git-send-email-mel@csn.ul.ie> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1244466090-10711-3-git-send-email-mel@csn.ul.ie> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4260 Lines: 85 On Mon, Jun 08, 2009 at 09:01:29PM +0800, Mel Gorman wrote: > On NUMA machines, the administrator can configure zone_relcaim_mode that > is a more targetted form of direct reclaim. On machines with large NUMA > distances for example, a zone_reclaim_mode defaults to 1 meaning that clean > unmapped pages will be reclaimed if the zone watermarks are not being met. > > There is a heuristic that determines if the scan is worthwhile but the > problem is that the heuristic is not being properly applied and is basically > assuming zone_reclaim_mode is 1 if it is enabled. > > This patch makes zone_reclaim() makes a better attempt at working out how > many pages it might be able to reclaim given the current reclaim_mode. If it > cannot clean pages, then NR_FILE_DIRTY number of pages are not candidates. If > it cannot swap, then NR_FILE_MAPPED are not. This indirectly addresses tmpfs > as those pages tend to be dirty as they are not cleaned by pdflush or sync. > > The ideal would be that the number of tmpfs pages would also be known > and account for like NR_FILE_MAPPED as swap is required to discard them. > A means of working this out quickly was not obvious but a comment is added > noting the problem. > > Signed-off-by: Mel Gorman > --- > mm/vmscan.c | 18 ++++++++++++++++-- > 1 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index ba211c1..ffe2f32 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2380,6 +2380,21 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) > { > int node_id; > int ret; > + int pagecache_reclaimable; > + > + /* > + * Work out how many page cache pages we can reclaim in this mode. > + * > + * NOTE: Ideally, tmpfs pages would be accounted as if they were > + * NR_FILE_MAPPED as swap is required to discard those > + * pages even when they are clean. However, there is no > + * way of quickly identifying the number of tmpfs pages > + */ > + pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); > + if (!(zone_reclaim_mode & RECLAIM_WRITE)) > + pagecache_reclaimable -= zone_page_state(zone, NR_FILE_DIRTY); > + if (!(zone_reclaim_mode & RECLAIM_SWAP)) > + pagecache_reclaimable -= zone_page_state(zone, NR_FILE_MAPPED); Your patch seems to conflict with KOSAKI's earlier patch "vmscan: change the number of the unmapped files in zone reclaim", where he offers a better way for getting rid of the tmpfs pages: + nr_file_pages = zone_page_state(zone, NR_INACTIVE_FILE) + + zone_page_state(zone, NR_ACTIVE_FILE); + nr_mapped = zone_page_state(zone, NR_FILE_MAPPED); + if (likely(nr_file_pages >= nr_mapped)) + nr_unmapped_file_pages = nr_file_pages - nr_mapped; if (nr_unmapped_file_pages > zone->min_unmapped_pages) { Thanks, Fengguang > /* > * Zone reclaim reclaims unmapped file backed pages and > @@ -2391,8 +2406,7 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) > * if less than a specified percentage of the zone is used by > * unmapped file backed pages. > */ > - if (zone_page_state(zone, NR_FILE_PAGES) - > - zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages > + if (pagecache_reclaimable <= zone->min_unmapped_pages > && zone_page_state(zone, NR_SLAB_RECLAIMABLE) > <= zone->min_slab_pages) > return 0; > -- > 1.5.6.5 -- 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/