Messages in this thread | | | Date | Mon, 1 Aug 2011 00:17:49 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH 6/8] mm: vmscan: Throttle reclaim if encountering too many dirty pages under writeback |
| |
On Thu, Jul 21, 2011 at 05:28:48PM +0100, Mel Gorman wrote: > Workloads that are allocating frequently and writing files place a > large number of dirty pages on the LRU. With use-once logic, it is > possible for them to reach the end of the LRU quickly requiring the > reclaimer to scan more to find clean pages. Ordinarily, processes that > are dirtying memory will get throttled by dirty balancing but this > is a global heuristic and does not take into account that LRUs are > maintained on a per-zone basis. This can lead to a situation whereby > reclaim is scanning heavily, skipping over a large number of pages > under writeback and recycling them around the LRU consuming CPU. > > This patch checks how many of the number of pages isolated from the > LRU were dirty. If a percentage of them are dirty, the process will be > throttled if a blocking device is congested or the zone being scanned > is marked congested. The percentage that must be dirty depends on > the priority. At default priority, all of them must be dirty. At > DEF_PRIORITY-1, 50% of them must be dirty, DEF_PRIORITY-2, 25% > etc. i.e. as pressure increases the greater the likelihood the process > will get throttled to allow the flusher threads to make some progress. > > Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
-- Kind regards, Minchan Kim
| |