linux-kernel - Re: [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low

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Date:	Mon, 1 Nov 2010 16:06:12 +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>,
	Shaohua Li <shaohua.li@...el.com>,
	Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 1/2] mm: page allocator: Adjust the per-cpu counter threshold when memory is low

> To ensure that kswapd wakes up, a safe version of zone_watermark_ok()
> is introduced that takes a more accurate reading of NR_FREE_PAGES when
> called from wakeup_kswapd, when deciding whether it is really safe to go
> back to sleep in sleeping_prematurely() and when deciding if a zone is
> really balanced or not in balance_pgdat(). We are still using an expensive
> function but limiting how often it is called.
> 
> When the test case is reproduced, the time spent in the watermark functions
> is reduced. The following report is on the percentage of time spent
> cumulatively spent in the functions zone_nr_free_pages(), zone_watermark_ok(),
> __zone_watermark_ok(), zone_watermark_ok_safe(), zone_page_state_snapshot(),
> zone_page_state().
> 
> vanilla                      11.6615%
> disable-threshold            0.2584%
> 
> Reported-by: Shaohua Li <shaohua.li@...el.com>
> Signed-off-by: Mel Gorman <mel@....ul.ie>

Except kamezawa-san pointed piece

Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>


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