2.6.30-stable review patch. If anyone has any objections, please let us know. ------------------ From: Mel Gorman commit 24cf72518c79cdcda486ed26074ff8151291cf65 upstream. 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. [akpm@linux-foundation.org: name things consistently] Signed-off-by: Mel Gorman Reviewed-by: Rik van Riel Cc: Christoph Lameter Reviewed-by: KOSAKI Motohiro Cc: Wu Fengguang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/vmstat.h | 3 +++ mm/vmscan.c | 3 +++ mm/vmstat.c | 3 +++ 3 files changed, 9 insertions(+) --- a/include/linux/vmstat.h +++ b/include/linux/vmstat.h @@ -36,6 +36,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS FOR_ALL_ZONES(PGSTEAL), FOR_ALL_ZONES(PGSCAN_KSWAPD), FOR_ALL_ZONES(PGSCAN_DIRECT), +#ifdef CONFIG_NUMA + PGSCAN_ZONE_RECLAIM_FAILED, +#endif PGINODESTEAL, SLABS_SCANNED, KSWAPD_STEAL, KSWAPD_INODESTEAL, PAGEOUTRUN, ALLOCSTALL, PGROTATED, #ifdef CONFIG_HUGETLB_PAGE --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2452,6 +2452,9 @@ int zone_reclaim(struct zone *zone, gfp_ ret = __zone_reclaim(zone, gfp_mask, order); zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); + if (!ret) + count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); + return ret; } #endif --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -675,6 +675,9 @@ static const char * const vmstat_text[] TEXTS_FOR_ZONES("pgscan_kswapd") TEXTS_FOR_ZONES("pgscan_direct") +#ifdef CONFIG_NUMA + "zone_reclaim_failed", +#endif "pginodesteal", "slabs_scanned", "kswapd_steal", -- 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/