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

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Message-ID: <CABPqkBROriDQa5-b-w45zV+2gS94oEW1c_bYwGmYAeYcqPoUog@mail.gmail.com>
Date:	Tue, 11 Feb 2014 11:58:45 +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 11:52 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Feb 11, 2014 at 11:35:45AM +0100, Stephane Eranian wrote:
>> On Tue, Feb 11, 2014 at 8:14 AM, Peter Zijlstra <peterz@...radead.org> wrote:
>> >
>> > That blows; how much is missing?
>>
>> They need to annotate load and stores. I asked for that feature a while ago.
>> It will come.
>
> And there is no way to deduce the information? We have type information
> for all arguments and local variables, right? So we can follow that.
>
> struct foo {
>         int ponies;
>         int moar_ponies;
> };
>
> struct bar {
>         int my_ponies;
>         struct foo *foo;
> };
>
> int moo(struct bar *bar)
> {
>         return bar->foo->moar_ponies;
> }
>
> Since we have the argument type, we can find the type for both loads,
> the first load:
>
>   *bar+8, we know is: struct foo * bar::foo
>   *foo+4, we know is: int foo::moar_ponies
>
> Or am I missing something?

How do you know that load at addr 0x1000 is accessing variable bar?
The IP gives you line number, and then what?
I think dwarf has the mapping regs -> variable and yes, the type info.
But I am not sure that's enough.
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