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authorMel Gorman <mel@csn.ul.ie>2010-10-26 14:21:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 16:52:07 -0700
commit0e093d99763eb4cea09f8ca4f1d01f34e121d10b (patch)
treefad38f9c3651c81db298521141a79d9468f71986 /mm/page_alloc.c
parent08fc468f4eaf6683bae5bdb94743a09d8630cb80 (diff)
downloadblackbird-op-linux-0e093d99763eb4cea09f8ca4f1d01f34e121d10b.tar.gz
blackbird-op-linux-0e093d99763eb4cea09f8ca4f1d01f34e121d10b.zip
writeback: do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone
If congestion_wait() is called with no BDI congested, the caller will sleep for the full timeout and this may be an unnecessary sleep. This patch adds a wait_iff_congested() that checks congestion and only sleeps if a BDI is congested else, it calls cond_resched() to ensure the caller is not hogging the CPU longer than its quota but otherwise will not sleep. This is aimed at reducing some of the major desktop stalls reported during IO. For example, while kswapd is operating, it calls congestion_wait() but it could just have been reclaiming clean page cache pages with no congestion. Without this patch, it would sleep for a full timeout but after this patch, it'll just call schedule() if it has been on the CPU too long. Similar logic applies to direct reclaimers that are not making enough progress. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Minchan Kim <minchan.kim@gmail.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r--mm/page_alloc.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6a683f819439..b13bc5e5bd7d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1907,7 +1907,7 @@ __alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order,
preferred_zone, migratetype);
if (!page && gfp_mask & __GFP_NOFAIL)
- congestion_wait(BLK_RW_ASYNC, HZ/50);
+ wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/50);
} while (!page && (gfp_mask & __GFP_NOFAIL));
return page;
@@ -2095,7 +2095,7 @@ rebalance:
pages_reclaimed += did_some_progress;
if (should_alloc_retry(gfp_mask, order, pages_reclaimed)) {
/* Wait for some write requests to complete then retry */
- congestion_wait(BLK_RW_ASYNC, HZ/50);
+ wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/50);
goto rebalance;
}
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