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From: Mel Gorman on 5 Aug 2010 11:10
On Thu, Aug 05, 2010 at 03:13:03PM +0900, KOSAKI Motohiro wrote:
> congestion_wait() mean "waiting quueue congestion is cleared".
> That said, if the system have plenty dirty pages and flusher thread push
> new request to IO queue conteniously, IO queue are not cleared
> congestion status for long time. thus, congestion_wait(HZ/10) become
> almostly equivalent schedule_timeout(HZ/10).
>
> However, synchronous lumpy reclaim donesn't need this
> congestion_wait() at all. shrink_page_list(PAGEOUT_IO_SYNC) are
> using wait_on_page_writeback() and it provide sufficient waiting.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com>

Needs rebasing for mmotm but otherwise;

Acked-by: Mel Gorman <mel(a)csn.ul.ie>

> ---
> mm/vmscan.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index cf51d62..1cdc3db 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1341,7 +1341,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
>
> /* Check if we should syncronously wait for writeback */
> if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
> - congestion_wait(BLK_RW_ASYNC, HZ/10);
> /*
> * The attempt at page out may have made some
> * of the pages active, mark them inactive again.
> --
> 1.6.5.2
>
>
>

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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