linux-kernel - Re: [PATCH 1/6] tracing, page-allocator: Add trace events for page allocation and page freeing

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Message-ID: <20090807104905.GA18134@csn.ul.ie>
Date:	Fri, 7 Aug 2009 11:49:06 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Ingo Molnar <mingo@...e.hu>
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 1/6] tracing, page-allocator: Add trace events for page
	allocation and page freeing

On Fri, Aug 07, 2009 at 09:50:30AM +0200, Ingo Molnar wrote:
> 
> * Mel Gorman <mel@....ul.ie> wrote:
> 
> > +TRACE_EVENT(mm_pagevec_free,
> 
> > +	TP_fast_assign(
> > +		__entry->page		= page;
> > +		__entry->order		= order;
> > +		__entry->cold		= cold;
> > +	),
> 
> > -	while (--i >= 0)
> > +	while (--i >= 0) {
> > +		trace_mm_pagevec_free(pvec->pages[i], 0, pvec->cold);
> >  		free_hot_cold_page(pvec->pages[i], pvec->cold);
> > +	}
> 
> Pagevec freeing has order 0 implicit, so you can further optimize 
> this by leaving out the 'order' field and using this format string:
> 
> +	TP_printk("page=%p pfn=%lu order=0 cold=%d",
> +                       __entry->page,
> +                       page_to_pfn(__entry->page),
> +                       __entry->cold)
> 
> the trace record becomes smaller by 4 bytes and the tracepoint 
> fastpath becomes shorter as well.
> 

Good point. It's fixed now.

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