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Date: Wed, 10 Jun 2009 10:53:55 +0900 (JST) From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> To: Mel Gorman <mel@....ul.ie> Cc: kosaki.motohiro@...fujitsu.com, Rik van Riel <riel@...hat.com>, Christoph Lameter <cl@...ux-foundation.org>, yanmin.zhang@...el.com, Wu Fengguang <fengguang.wu@...el.com>, linuxram@...ibm.com, linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 4/4] Reintroduce zone_reclaim_interval for when zone_reclaim() scans and fails to avoid CPU spinning at 100% on NUMA > + > +zone_reclaim_interval: > + > +The time allowed for off-node allocations after zone reclaim > +has failed to reclaim enough pages to allow a local allocation. > + > +Time is set in seconds and set by default to 30 seconds. > + > +Reduce the interval if undesired off-node allocations occur or > +set to 0 to always try and reclaim pages for node-local memory. > +However, too frequent scans will have a negative impact on > +off-node allocation performance and manifest as high CPU usage. > + good documentaion :) Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> -kosaki > ============ End of Document ================================= > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 8895985..3a53e1c 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -335,6 +335,15 @@ struct zone { > atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS]; > > /* > + * timestamp (in jiffies) of the last zone_reclaim that scanned > + * but failed to free enough pages. This is used to avoid repeated > + * scans when zone_reclaim() is unable to detect in advance that > + * the scanning is useless. This can happen for example if a zone > + * has large numbers of clean unmapped file pages on tmpfs > + */ > + unsigned long zone_reclaim_failure; > + > + /* > * prev_priority holds the scanning priority for this zone. It is > * defined as the scanning priority at which we achieved our reclaim > * target at the previous try_to_free_pages() or balance_pgdat() > diff --git a/include/linux/swap.h b/include/linux/swap.h > index c88b366..28a01e3 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -225,6 +225,7 @@ extern long vm_total_pages; > > #ifdef CONFIG_NUMA > extern int zone_reclaim_mode; > +extern int zone_reclaim_interval; > extern int sysctl_min_unmapped_ratio; > extern int sysctl_min_slab_ratio; > extern int zone_reclaim(struct zone *, gfp_t, unsigned int); > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 0554886..2afffa5 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -1221,6 +1221,15 @@ static struct ctl_table vm_table[] = { > .extra1 = &zero, > }, > { > + .ctl_name = CTL_UNNUMBERED, > + .procname = "zone_reclaim_interval", > + .data = &zone_reclaim_interval, > + .maxlen = sizeof(zone_reclaim_interval), > + .mode = 0644, > + .proc_handler = &proc_dointvec_jiffies, > + .strategy = &sysctl_jiffies, > + }, > + { > .ctl_name = VM_MIN_UNMAPPED, > .procname = "min_unmapped_ratio", > .data = &sysctl_min_unmapped_ratio, > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 8be4582..5fa4843 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2315,6 +2315,13 @@ int zone_reclaim_mode __read_mostly; > #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ > > /* > + * Minimum time between zone_reclaim() scans that failed. Ordinarily, a > + * scan will not fail because it will be determined in advance if it can > + * succeeed but this does not always work. See mmzone.h > + */ > +int zone_reclaim_interval __read_mostly = 30*HZ; > + > +/* > * Priority for ZONE_RECLAIM. This determines the fraction of pages > * of a node considered for each zone_reclaim. 4 scans 1/16th of > * a zone. > @@ -2464,6 +2471,15 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) > zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) > return ZONE_RECLAIM_FULL; > > + /* Watch for jiffie wraparound */ > + if (unlikely(jiffies < zone->zone_reclaim_failure)) > + zone->zone_reclaim_failure = jiffies; > + > + /* Do not attempt a scan if scanning failed recently */ > + if (time_before(jiffies, > + zone->zone_reclaim_failure + zone_reclaim_interval)) > + return ZONE_RECLAIM_FULL; > + > if (zone_is_all_unreclaimable(zone)) > return ZONE_RECLAIM_FULL; > > @@ -2491,6 +2507,14 @@ int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) > > if (!ret) { > count_vm_events(PGSCAN_ZONERECLAIM_FAILED, 1); > + > + /* > + * We were unable to reclaim enough pages to stay on node and > + * unable to detect in advance that the scan would fail. Allow > + * off node accesses for zone_reclaim_inteval jiffies before > + * trying zone_reclaim() again > + */ > + zone->zone_reclaim_failure = jiffies; > } > > return ret; > -- > 1.5.6.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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