linux-kernel - Re: [PATCH 2/6] tracing, page-allocator: Add trace events for anti-fragmentation falling back to other migratetypes

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Message-ID: <20090807080249.GA21821@elte.hu>
Date:	Fri, 7 Aug 2009 10:02:49 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Larry Woodman <lwoodman@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, riel@...hat.com,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH 2/6] tracing, page-allocator: Add trace events for
	anti-fragmentation falling back to other migratetypes


* Mel Gorman <mel@....ul.ie> wrote:

> +++ b/mm/page_alloc.c
> @@ -839,6 +839,12 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
>  							start_migratetype);
>  
>  			expand(zone, page, order, current_order, area, migratetype);
> +
> +			trace_mm_page_alloc_extfrag(page, order, current_order,
> +				start_migratetype, migratetype,
> +				current_order < pageblock_order,
> +				migratetype == start_migratetype);

This tracepoint too should be optimized some more:

 - pageblock_order can be passed down verbatim instead of the 
   'current_order < pageblock_order': it means one comparison less 
   in the fast-path, plus it gives more trace information as well.

 - migratetype == start_migratetype check is superfluous as both 
   values are already traced. This property can be added to the 
   TP_printk() post-processing stage instead, if the pretty-printing 
   is desired.

	Ingo
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