linux-kernel - Re: [PATCH 2/2] mm/page_ref: add tracepoint to track down page reference manipulation

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Date:	Thu, 10 Dec 2015 13:07:29 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Nazarewicz <mina86@...a86.com>,
	Minchan Kim <minchan@...nel.org>, Mel Gorman <mgorman@...e.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH 2/2] mm/page_ref: add tracepoint to track down page
 reference manipulation

On Wed, Dec 09, 2015 at 10:36:48PM -0500, Steven Rostedt wrote:
> On Thu, 10 Dec 2015 11:50:15 +0900
> Joonsoo Kim <iamjoonsoo.kim@....com> wrote:
> 
> > Output of cpu 3, 7 are mixed and it's not easy to analyze it.
> > 
> > I think that it'd be better not to sort stack trace. How do
> > you think about it? Could you fix it, please?
> 
> It may not be that easy to fix because of the sorting algorithm. That
> would require looking going ahead one more event each time and then
> checking if its a stacktrace. I may look at it and see if I can come up
> with something that's not too invasive in the algorithms.

Okay.

> That said, for now you can use the --cpu option. I'm not sure I ever
> documented it as it was originally added for debugging, but I use it
> enough that it may be worth while to officially support it.
> 
>  trace-cmd report --cpu 3
> 
> Will show you just cpu 3 and nothing else. Which is what I use a lot.

Thanks for the input. It works but it's not sufficient to me.
Page reference is manipulated by multiple cpus so it's better to
analyze unified output.

> 
> But doing the stack trace thing may be something to fix as well. I'll
> see what I can do, but no guarantees.

Okay. Don't be hurry. :)
trace-cmd is excellent and works well for me as it is.

Thanks.
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