linux-kernel - Re: [PATCH 11/25] Calculate the cold parameter for allocation only once

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Message-Id: <20090421180551.F142.A69D9226@jp.fujitsu.com>
Date:	Tue, 21 Apr 2009 18:07:24 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 11/25] Calculate the cold parameter for allocation only once

> GFP mask is checked for __GFP_COLD has been specified when deciding which
> end of the PCP lists to use. However, it is happening multiple times per
> allocation, at least once per zone traversed. Calculate it once.
> 
> Signed-off-by: Mel Gorman <mel@....ul.ie>
> ---
>  mm/page_alloc.c |   35 ++++++++++++++++++-----------------
>  1 files changed, 18 insertions(+), 17 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 1506cd5..51e1ded 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1066,11 +1066,10 @@ void split_page(struct page *page, unsigned int order)
>   */
>  static struct page *buffered_rmqueue(struct zone *preferred_zone,
>  			struct zone *zone, int order, gfp_t gfp_flags,
> -			int migratetype)
> +			int migratetype, int cold)
>  {
>  	unsigned long flags;
>  	struct page *page;
> -	int cold = !!(gfp_flags & __GFP_COLD);
>  	int cpu;

Honestly, I don't like this ;-)

It seems benefit is too small. It don't win against code ugliness, I think.





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