Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932365AbVLHUhq (ORCPT ); Thu, 8 Dec 2005 15:37:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932363AbVLHUhp (ORCPT ); Thu, 8 Dec 2005 15:37:45 -0500 Received: from omx1-ext.sgi.com ([192.48.179.11]:42634 "EHLO omx1.americas.sgi.com") by vger.kernel.org with ESMTP id S932350AbVLHUho (ORCPT ); Thu, 8 Dec 2005 15:37:44 -0500 Date: Thu, 8 Dec 2005 12:37:17 -0800 (PST) From: Christoph Lameter To: akpm@osdl.org Cc: Christoph Hellwig , linux-ia64@vger.kernel.org, steiner@sgi.com, linux-kernel@vger.kernel.org, ak@suse.de, Wu Fengguang , Christoph Lameter Message-Id: <20051208203717.30456.17434.sendpatchset@schroedinger.engr.sgi.com> In-Reply-To: <20051208203707.30456.57439.sendpatchset@schroedinger.engr.sgi.com> References: <20051208203707.30456.57439.sendpatchset@schroedinger.engr.sgi.com> Subject: [PATCH 3/3] Zone reclaim V3: Frequency of failed reclaim attempts Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2831 Lines: 66 Reduce frequency of unsuccessful zone reclaim attempts It is unlikely that zone reclaim is successful once it has failed. The performance of the page allocator will sink signficantly for off-node allocation if every page allocation attempt first requires a zone reclaim scan to establish that no local memory is availale. This patch limits the number of unsuccessful zone reclaim attempts to one per tick by remembering the last time a zone reclaim failed on a zone. Note that this approach may be avoided once we have per zone statistics on the number of unmapped (==easily reclaimable) pages. I am working on a statistics patch that may allow keeping track of unmapped pages per zone. A check of that number may then allow an easy determination if it makes sense to run zone reclaim. Signed-off-by: Christoph Lameter Index: linux-2.6.15-rc4/mm/vmscan.c =================================================================== --- linux-2.6.15-rc4.orig/mm/vmscan.c 2005-12-08 11:10:14.000000000 -0800 +++ linux-2.6.15-rc4/mm/vmscan.c 2005-12-08 12:04:38.000000000 -0800 @@ -1379,6 +1379,16 @@ int zone_reclaim(struct zone *zone, gfp_ atomic_read(&zone->reclaim_in_progress) > 0) return 0; + /* + * If an unsuccessful zone reclaim occurred in this tick then we + * already needed to go off before. Our local purity is already + * tainted and its likely that the scan for easily reclaimable pages + * will be a waste of time. Continue off node allocations for the + * duration of this tick. + */ + if (zone->last_unsuccessful_zone_reclaim == get_jiffies_64()) + return 0; + sc.gfp_mask = gfp_mask; sc.may_writepage = 0; sc.may_swap = 0; @@ -1397,6 +1407,8 @@ int zone_reclaim(struct zone *zone, gfp_ shrink_zone(zone, &sc); p->reclaim_state = NULL; current->flags &= ~PF_MEMALLOC; + if (sc.nr_reclaimed == 0) + zone->last_unsuccessful_zone_reclaim = get_jiffies_64(); cond_resched(); return sc.nr_reclaimed >= (1 << order); } Index: linux-2.6.15-rc4/include/linux/mmzone.h =================================================================== --- linux-2.6.15-rc4.orig/include/linux/mmzone.h 2005-12-08 11:10:14.000000000 -0800 +++ linux-2.6.15-rc4/include/linux/mmzone.h 2005-12-08 12:00:43.000000000 -0800 @@ -153,6 +153,8 @@ struct zone { /* A count of how many reclaimers are scanning this zone */ atomic_t reclaim_in_progress; + unsigned long last_unsuccessful_zone_reclaim; + /* * prev_priority holds the scanning priority for this zone. It is * defined as the scanning priority at which we achieved our reclaim - 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/