linux-kernel - Re: [PATCH 1/4] vmscan: delegate pageout io to flusher thread if current is kswapd

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Message-Id: <20100415171750.D195.A69D9226@jp.fujitsu.com>
Date:	Thu, 15 Apr 2010 17:18:56 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com, Dave Chinner <david@...morbit.com>,
	Mel Gorman <mel@....ul.ie>,
	Chris Mason <chris.mason@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 1/4] vmscan: delegate pageout io to flusher thread if current is kswapd

> 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@...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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