linux-kernel - Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in direct reclaim

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Message-ID: <20110714061915.GN7529@suse.de>
Date:	Thu, 14 Jul 2011 07:19:15 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	XFS <xfs@....sgi.com>, Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>,
	Johannes Weiner <jweiner@...hat.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Rik van Riel <riel@...hat.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH 1/5] mm: vmscan: Do not writeback filesystem pages in
 direct reclaim

On Thu, Jul 14, 2011 at 10:38:01AM +0900, KAMEZAWA Hiroyuki wrote:
> > @@ -825,6 +825,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> >  		if (PageDirty(page)) {
> >  			nr_dirty++;
> >  
> > +			/*
> > +			 * Only kswapd can writeback filesystem pages to
> > +			 * avoid risk of stack overflow
> > +			 */
> > +			if (page_is_file_cache(page) && !current_is_kswapd()) {
> > +				inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
> > +				goto keep_locked;
> > +			}
> > +
> 
> 
> This will cause tons of memcg OOM kill because we have no help of kswapd (now).
> 
> Could you make this
> 
> 	if (scanning_global_lru(sc) && page_is_file_cache(page) && !current_is_kswapd())
> ...
> 

I can, but as Christoph points out, the request is already being
ignored so how will it help?

-- 
Mel Gorman
SUSE Labs
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