linux-kernel - Re: [Questions] perf c2c: What's the current status of perf c2c?

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Message-ID: <CABPqkBSR+haJr-uzn3xjbP5aZ_x70FDi7ufgJi3wW7PitfqBwA@mail.gmail.com>
Date:	Wed, 9 Dec 2015 09:15:04 -0800
From:	Stephane Eranian <eranian@...gle.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Yunlong Song <yunlong.song@...wei.com>,
	Don Zickus <dzickus@...hat.com>,
	David Ahern <dsahern@...il.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Joe Mario <jmario@...hat.com>, Mike Galbraith <efault@....de>,
	Paul Mackerras <paulus@...ba.org>,
	Richard Fowles <rfowles@...hat.com>,
	"acme@...nel.org >> Arnaldo Carvalho de Melo" <acme@...nel.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...nel.org>,
	"wangnan0@...wei.com >> Wang Nan" <wangnan0@...wei.com>,
	Richard Fowles <fowles@...each.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [Questions] perf c2c: What's the current status of perf c2c?

Hi,

On Wed, Dec 9, 2015 at 8:58 AM, Andi Kleen <andi@...stfloor.org> wrote:
>> > the plan for me is to to use it some more to prove it's useful
>> > and kick it to be merged with perf at some point
>>
>> So I never really liked the c2c tool because it was so narrowly
>> focussed, it only works on NUMA thingies IIRC.
>
> It should work on all systems with an Intel Core (not Atom)
>
> However it was never clear to me if the tool was any better
> than simply sampling for
>
> mem_load_uops_l3_hit_retired.xsnp_hitm:pp    (local socket)
> mem_load_uops_l3_miss_retired.remote_hitm:pp (remote socket)
>
> which gives you instructions that reference bouncing cache lines.
>
If I recall the c2c tool is giving you more than the bouncing line. It shows you
the offset inside the line and the participating CPUs.
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