linux-kernel - Re: [PATCH 12/14] vmscan: Do not writeback pages in direct reclaim

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Message-Id: <20100706200310.CD06.A69D9226@jp.fujitsu.com>
Date:	Tue,  6 Jul 2010 20:13:36 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>
Subject: Re: [PATCH 12/14] vmscan: Do not writeback pages in direct reclaim

> On Tue, Jul 06, 2010 at 09:36:41AM +0900, KOSAKI Motohiro wrote:
> > Hello,
> > 
> > > Ok, that's reasonable as I'm still working on that patch. For example, the
> > > patch disabled anonymous page writeback which is unnecessary as the stack
> > > usage for anon writeback is less than file writeback. 
> > 
> > How do we examine swap-on-file?
> > 
> 
> Anything in particular wrong with the following?
> 
> /*
>  * For now, only kswapd can writeback filesystem pages as otherwise
>  * there is a stack overflow risk
>  */
> static inline bool reclaim_can_writeback(struct scan_control *sc,
>                                         struct page *page)
> {
>         return !page_is_file_cache(page) || current_is_kswapd();
> }
> 
> Even if it is a swapfile, I didn't spot a case where the filesystems
> writepage would be called. Did I miss something?

Hmm...

Now, I doubt I don't understand your mention. Do you mean you intend to swtich task
stack when every writepage? It seems a bit costly. but otherwise write-page for anon
makes filesystem IO and stack-overflow.

Can you please elaborate your plan?



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