diff options
author | Andrea Arcangeli <aarcange@redhat.com> | 2011-03-23 02:30:38 +0300 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-23 03:44:00 +0300 |
commit | d527caf22e48480b102c7c6ee5b9ba12170148f7 (patch) | |
tree | 7d53a2c430f8c020b6fa8390396dd2d1ce480b9a | |
parent | 89699605fe7cfd8611900346f61cb6cbf179b10a (diff) | |
download | linux-d527caf22e48480b102c7c6ee5b9ba12170148f7.tar.xz |
mm: compaction: prevent kswapd compacting memory to reduce CPU usage
This patch reverts 5a03b051 ("thp: use compaction in kswapd for GFP_ATOMIC
order > 0") due to reports stating that kswapd CPU usage was higher and
IRQs were being disabled more frequently. This was reported at
http://www.spinics.net/linux/fedora/alsa-user/msg09885.html.
Without this patch applied, CPU usage by kswapd hovers around the 20% mark
according to the tester (Arthur Marsh:
http://www.spinics.net/linux/fedora/alsa-user/msg09899.html). With this
patch applied, it's around 2%.
The problem is not related to THP which specifies __GFP_NO_KSWAPD but is
triggered by high-order allocations hitting the low watermark for their
order and waking kswapd on kernels with CONFIG_COMPACTION set. The most
common trigger for this is network cards configured for jumbo frames but
it's also possible it'll be triggered by fork-heavy workloads (order-1)
and some wireless cards which depend on order-1 allocations.
The symptoms for the user will be high CPU usage by kswapd in low-memory
situations which could be confused with another writeback problem. While
a patch like 5a03b051 may be reintroduced in the future, this patch plays
it safe for now and reverts it.
[mel@csn.ul.ie: Beefed up the changelog]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reported-by: Arthur Marsh <arthur.marsh@internode.on.net>
Tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Cc: <stable@kernel.org> [2.6.38.1]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | include/linux/compaction.h | 9 | ||||
-rw-r--r-- | mm/compaction.c | 24 | ||||
-rw-r--r-- | mm/vmscan.c | 18 |
3 files changed, 6 insertions, 45 deletions
diff --git a/include/linux/compaction.h b/include/linux/compaction.h index dfa2ed4c0d26..cc9f7a428649 100644 --- a/include/linux/compaction.h +++ b/include/linux/compaction.h @@ -11,9 +11,6 @@ /* The full zone was compacted */ #define COMPACT_COMPLETE 3 -#define COMPACT_MODE_DIRECT_RECLAIM 0 -#define COMPACT_MODE_KSWAPD 1 - #ifdef CONFIG_COMPACTION extern int sysctl_compact_memory; extern int sysctl_compaction_handler(struct ctl_table *table, int write, @@ -28,8 +25,7 @@ extern unsigned long try_to_compact_pages(struct zonelist *zonelist, bool sync); extern unsigned long compaction_suitable(struct zone *zone, int order); extern unsigned long compact_zone_order(struct zone *zone, int order, - gfp_t gfp_mask, bool sync, - int compact_mode); + gfp_t gfp_mask, bool sync); /* Do not skip compaction more than 64 times */ #define COMPACT_MAX_DEFER_SHIFT 6 @@ -74,8 +70,7 @@ static inline unsigned long compaction_suitable(struct zone *zone, int order) } static inline unsigned long compact_zone_order(struct zone *zone, int order, - gfp_t gfp_mask, bool sync, - int compact_mode) + gfp_t gfp_mask, bool sync) { return COMPACT_CONTINUE; } diff --git a/mm/compaction.c b/mm/compaction.c index 8be430b812de..dcb058bd76c4 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -42,8 +42,6 @@ struct compact_control { unsigned int order; /* order a direct compactor needs */ int migratetype; /* MOVABLE, RECLAIMABLE etc */ struct zone *zone; - - int compact_mode; }; static unsigned long release_freepages(struct list_head *freelist) @@ -397,10 +395,7 @@ static int compact_finished(struct zone *zone, return COMPACT_COMPLETE; /* Compaction run is not finished if the watermark is not met */ - if (cc->compact_mode != COMPACT_MODE_KSWAPD) - watermark = low_wmark_pages(zone); - else - watermark = high_wmark_pages(zone); + watermark = low_wmark_pages(zone); watermark += (1 << cc->order); if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) @@ -413,15 +408,6 @@ static int compact_finished(struct zone *zone, if (cc->order == -1) return COMPACT_CONTINUE; - /* - * Generating only one page of the right order is not enough - * for kswapd, we must continue until we're above the high - * watermark as a pool for high order GFP_ATOMIC allocations - * too. - */ - if (cc->compact_mode == COMPACT_MODE_KSWAPD) - return COMPACT_CONTINUE; - /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { /* Job done if page is free of the right migratetype */ @@ -543,8 +529,7 @@ static int compact_zone(struct zone *zone, struct compact_control *cc) unsigned long compact_zone_order(struct zone *zone, int order, gfp_t gfp_mask, - bool sync, - int compact_mode) + bool sync) { struct compact_control cc = { .nr_freepages = 0, @@ -553,7 +538,6 @@ unsigned long compact_zone_order(struct zone *zone, .migratetype = allocflags_to_migratetype(gfp_mask), .zone = zone, .sync = sync, - .compact_mode = compact_mode, }; INIT_LIST_HEAD(&cc.freepages); INIT_LIST_HEAD(&cc.migratepages); @@ -599,8 +583,7 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist, nodemask) { int status; - status = compact_zone_order(zone, order, gfp_mask, sync, - COMPACT_MODE_DIRECT_RECLAIM); + status = compact_zone_order(zone, order, gfp_mask, sync); rc = max(status, rc); /* If a normal allocation would succeed, stop compacting */ @@ -631,7 +614,6 @@ static int compact_node(int nid) .nr_freepages = 0, .nr_migratepages = 0, .order = -1, - .compact_mode = COMPACT_MODE_DIRECT_RECLAIM, }; zone = &pgdat->node_zones[zoneid]; diff --git a/mm/vmscan.c b/mm/vmscan.c index 6771ea70bfe7..3b4a41d72489 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2397,7 +2397,6 @@ loop_again: * cause too much scanning of the lower zones. */ for (i = 0; i <= end_zone; i++) { - int compaction; struct zone *zone = pgdat->node_zones + i; int nr_slab; @@ -2428,24 +2427,9 @@ loop_again: sc.nr_reclaimed += reclaim_state->reclaimed_slab; total_scanned += sc.nr_scanned; - compaction = 0; - if (order && - zone_watermark_ok(zone, 0, - high_wmark_pages(zone), - end_zone, 0) && - !zone_watermark_ok(zone, order, - high_wmark_pages(zone), - end_zone, 0)) { - compact_zone_order(zone, - order, - sc.gfp_mask, false, - COMPACT_MODE_KSWAPD); - compaction = 1; - } - if (zone->all_unreclaimable) continue; - if (!compaction && nr_slab == 0 && + if (nr_slab == 0 && !zone_reclaimable(zone)) zone->all_unreclaimable = 1; /* |