diff options
| author | Andrea Arcangeli <aarcange@redhat.com> | 2011-03-23 00:30:38 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-03-23 01:44:00 +0100 |
| commit | d527caf22e48480b102c7c6ee5b9ba12170148f7 (patch) | |
| tree | 7d53a2c430f8c020b6fa8390396dd2d1ce480b9a /include | |
| parent | mm: vmap area cache (diff) | |
| download | linux-d527caf22e48480b102c7c6ee5b9ba12170148f7.tar.xz linux-d527caf22e48480b102c7c6ee5b9ba12170148f7.zip | |
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/compaction.h | 9 |
1 files changed, 2 insertions, 7 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; } |