From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757831AbZFIRCa (ORCPT ); Tue, 9 Jun 2009 13:02:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755315AbZFIRBr (ORCPT ); Tue, 9 Jun 2009 13:01:47 -0400 Received: from gir.skynet.ie ([193.1.99.77]:59495 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753979AbZFIRBp (ORCPT ); Tue, 9 Jun 2009 13:01:45 -0400 From: Mel Gorman To: Mel Gorman , KOSAKI Motohiro , Rik van Riel , Christoph Lameter , yanmin.zhang@intel.com, Wu Fengguang , linuxram@us.ibm.com Cc: linux-mm , LKML Subject: [PATCH 3/4] Count the number of times zone_reclaim() scans and fails Date: Tue, 9 Jun 2009 18:01:43 +0100 Message-Id: <1244566904-31470-4-git-send-email-mel@csn.ul.ie> X-Mailer: git-send-email 1.5.6.5 In-Reply-To: <1244566904-31470-1-git-send-email-mel@csn.ul.ie> References: <1244566904-31470-1-git-send-email-mel@csn.ul.ie> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On NUMA machines, the administrator can configure zone_reclaim_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 it is possible that the heuristic will fail and the CPU gets tied up scanning uselessly. Detecting the situation requires some guesswork and experimentation so this patch adds a counter "zreclaim_failed" to /proc/vmstat. If during high CPU utilisation this counter is increasing rapidly, then the resolution to the problem may be to set /proc/sys/vm/zone_reclaim_mode to 0. Signed-off-by: Mel Gorman --- include/linux/vmstat.h | 3 +++ mm/vmscan.c | 4 ++++ mm/vmstat.c | 3 +++ 3 files changed, 10 insertions(+), 0 deletions(-) diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h index ff4696c..416f748 100644 --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -36,6 +36,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, FOR_ALL_ZONES(PGSTEAL), FOR_ALL_ZONES(PGSCAN_KSWAPD), FOR_ALL_ZONES(PGSCAN_DIRECT), +#ifdef CONFIG_NUMA + PGSCAN_ZONERECLAIM_FAILED, +#endif PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL, PAGEOUTRUN, ALLOCSTALL, PGROTATED, #ifdef CONFIG_HUGETLB_PAGE diff --git a/mm/vmscan.c b/mm/vmscan.c index e862fc9..8be4582 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2489,6 +2489,10 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) ret = __zone_reclaim(zone, gfp_mask, order); zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); + if (!ret) { + count_vm_events(PGSCAN_ZONERECLAIM_FAILED, 1); + } + return ret; } #endif diff --git a/mm/vmstat.c b/mm/vmstat.c index 1e3aa81..02677d1 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -673,6 +673,9 @@ static const char * const vmstat_text[] = { TEXTS_FOR_ZONES("pgscan_kswapd") TEXTS_FOR_ZONES("pgscan_direct") +#ifdef CONFIG_NUMA + "zreclaim_failed", +#endif "pginodesteal", "slabs_scanned", "kswapd_steal", -- 1.5.6.5