linux-kernel - Re: [PATCH 00/21] perf, c2c: Add new tool to analyze cacheline contention on NUMA systems

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Date:	Tue, 11 Feb 2014 11:35:45 +0100
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Don Zickus <dzickus@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>, Joe Mario <jmario@...hat.com>,
	Richard Fowles <fowles@...each.com>
Subject: Re: [PATCH 00/21] perf, c2c: Add new tool to analyze cacheline
 contention on NUMA systems

On Tue, Feb 11, 2014 at 8:14 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Feb 10, 2014 at 11:21:53PM +0100, Stephane Eranian wrote:
>> On Mon, Feb 10, 2014 at 10:29 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> > On Mon, Feb 10, 2014 at 12:28:55PM -0500, Don Zickus wrote:
>> >> The data output is verbose and there are lots of data tables that interprit the latencies
>> >> and data addresses in different ways to help see where bottlenecks might be lying.
>> >
>> > Would be good to see what the output looks like.
>> >
>> > What I haven't seen; and what I would find most useful; is using the IP
>> > + dwarf info to map it back to a data structure member.
>> >
>> > Since you're already using the PEBS data-source fields, you can also
>> > have a precise IP. For many cases its possible to reconstruct the exact
>> > data member the instruction is modifying.
>> >
>> The tool already uses precise=2 to get the precise IP.
>>
>> To get from IP to data member, you'd need some debug info which is not
>> yet emitted
>> by the compiler.
>
> That blows; how much is missing?

They need to annotate load and stores. I asked for that feature a while ago.
It will come.
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