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

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Message-ID: <20100615114510.GE26788@csn.ul.ie>
Date:	Tue, 15 Jun 2010 12:45:11 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Rik van Riel <riel@...hat.com>
Cc:	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>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim

On Mon, Jun 14, 2010 at 05:55:51PM -0400, Rik van Riel wrote:
> On 06/14/2010 07:17 AM, Mel Gorman wrote:
>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 4856a2a..574e816 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -372,6 +372,12 @@ int write_reclaim_page(struct page *page, struct address_space *mapping,
>>   	return PAGE_SUCCESS;
>>   }
>>
>> +/* kswapd and memcg can writeback as they are unlikely to overflow stack */
>> +static inline bool reclaim_can_writeback(struct scan_control *sc)
>> +{
>> +	return current_is_kswapd() || sc->mem_cgroup != NULL;
>> +}
>> +
>
> I'm not entirely convinced on this bit, but am willing to
> be convinced by the data.
>

Which bit?

You're not convinced that kswapd should be allowed to write back?
You're not convinced that memcg should be allowed to write back?
You're not convinced that direct reclaim writing back pages can overflow
	the stack?

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