e55e18e57928b5c8331a0f0fa parent 273f047e36d83179573dc7e3a8af6aceaa8c599e author Mel Gorman 1260842333 -0800 committer Linus Torvalds 1260895996 -0800 vmscan: have kswapd sleep for a short interval and double check it should be asleep After kswapd balances all zones in a pgdat, it goes to sleep. In the event of no IO congestion, kswapd can go to sleep very shortly after the high watermark was reached. If there are a constant stream of allocations from parallel processes, it can mean that kswapd went to sleep too quickly and the high watermark is not being maintained for sufficient length time. This patch makes kswapd go to sleep as a two-stage process. It first tries to sleep for HZ/10. If it is woken up by another process or the high watermark is no longer met, it's considered a premature sleep and kswapd continues work. Otherwise it goes fully to sleep. This adds more counters to distinguish between fast and slow breaches of watermarks. A "fast" premature sleep is one where the low watermark was hit in a very short time after kswapd going to sleep. A "slow" premature sleep indicates that the high watermark was breached after a very short interval. Signed-off-by: Mel Gorman Cc: Frans Pop Cc: KOSAKI Motohiro Cc: Rik van Riel Cc: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds ¦G'³”$x