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

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Date:	Fri, 7 Aug 2009 11:57:33 +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 2/6] tracing, page-allocator: Add trace events for
	anti-fragmentation falling back to other migratetypes

On Fri, Aug 07, 2009 at 10:02:49AM +0200, Ingo Molnar wrote:
> 
> * 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.
> 

I think what you're saying that it's better to handle additional information
like this in TP_printk always. That's what I've changed both of these into
at least. I didn't even need to pass down pageblock_order because it should
be available in the post-processing context from a header.

The additional parameters are not being passed down any more and the
TP_printk looks like

        TP_printk("page=%p pfn=%lu alloc_order=%d fallback_order=%d pageblock_order=%d alloc_migratetype=%d fallback_migratetype=%d fragmenting=%d change_ownership=%d",
                __entry->page,
                page_to_pfn(__entry->page),
                __entry->alloc_order,
                __entry->fallback_order,
                pageblock_order,
                __entry->alloc_migratetype,
                __entry->fallback_migratetype,
                __entry->fallback_order < pageblock_order,
                __entry->alloc_migratetype == __entry->fallback_migratetype)

Is that what you meant?


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