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authorMel Gorman <mel@csn.ul.ie>2010-05-24 17:32:31 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-25 11:06:59 -0400
commit5e7719058079a1423ccce56148b0aaa56b2df821 (patch)
tree3666cb3d5540dcaa3d8e7df8c293a0ad603a181c /mm
parent56de7263fcf3eb10c8dcdf8d59a9cec831795f3f (diff)
mm: compaction: add a tunable that decides when memory should be compacted and when it should be reclaimed
The kernel applies some heuristics when deciding if memory should be compacted or reclaimed to satisfy a high-order allocation. One of these is based on the fragmentation. If the index is below 500, memory will not be compacted. This choice is arbitrary and not based on data. To help optimise the system and set a sensible default for this value, this patch adds a sysctl extfrag_threshold. The kernel will only compact memory if the fragmentation index is above the extfrag_threshold. [randy.dunlap@oracle.com: Fix build errors when proc fs is not configured] Signed-off-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Rik van Riel <riel@redhat.com> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/compaction.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index 9583e193dc4..94cce51b0b3 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -433,6 +433,8 @@ static unsigned long compact_zone_order(struct zone *zone,
433 return compact_zone(zone, &cc); 433 return compact_zone(zone, &cc);
434} 434}
435 435
436int sysctl_extfrag_threshold = 500;
437
436/** 438/**
437 * try_to_compact_pages - Direct compact to satisfy a high-order allocation 439 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
438 * @zonelist: The zonelist used for the current allocation 440 * @zonelist: The zonelist used for the current allocation
@@ -491,7 +493,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
491 * Only compact if a failure would be due to fragmentation. 493 * Only compact if a failure would be due to fragmentation.
492 */ 494 */
493 fragindex = fragmentation_index(zone, order); 495 fragindex = fragmentation_index(zone, order);
494 if (fragindex >= 0 && fragindex <= 500) 496 if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
495 continue; 497 continue;
496 498
497 if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) { 499 if (fragindex == -1 && zone_watermark_ok(zone, order, watermark, 0, 0)) {
@@ -572,6 +574,14 @@ int sysctl_compaction_handler(struct ctl_table *table, int write,
572 return 0; 574 return 0;
573} 575}
574 576
577int sysctl_extfrag_handler(struct ctl_table *table, int write,
578 void __user *buffer, size_t *length, loff_t *ppos)
579{
580 proc_dointvec_minmax(table, write, buffer, length, ppos);
581
582 return 0;
583}
584
575#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) 585#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
576ssize_t sysfs_compact_node(struct sys_device *dev, 586ssize_t sysfs_compact_node(struct sys_device *dev,
577 struct sysdev_attribute *attr, 587 struct sysdev_attribute *attr,