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SubjectRe: [PATCH 1/4] vmscan: delegate pageout io to flusher thread if current is kswapd
Date
> Now, vmscan pageout() is one of IO throuput degression source.
> Some IO workload makes very much order-0 allocation and reclaim
> and pageout's 4K IOs are making annoying lots seeks.
>
> At least, kswapd can avoid such pageout() because kswapd don't
> need to consider OOM-Killer situation. that's no risk.

I've found one bug in this patch myself. flusher thread don't
pageout anon pages. then, we need PageAnon() check ;)



>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> ---
> mm/vmscan.c | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 3ff3311..d392a50 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -614,6 +614,13 @@ static enum page_references page_check_references(struct page *page,
> if (referenced_page)
> return PAGEREF_RECLAIM_CLEAN;
>
> + /*
> + * Delegate pageout IO to flusher thread. They can make more
> + * effective IO pattern.
> + */
> + if (current_is_kswapd())
> + return PAGEREF_RECLAIM_CLEAN;
> +
> return PAGEREF_RECLAIM;
> }
>
> --
> 1.6.5.2
>
>
>





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