linux-kernel - Re: [RFC PATCH 2/9] perf: Add ability to dump user regs

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Message-ID: <AANLkTi=Ja1Yem9Nkdz06_ZxtvxGZUPbGYqusfcf3iN-G@mail.gmail.com>
Date:	Mon, 18 Oct 2010 12:01:18 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Tom Zanussi <tzanussi@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Robert Richter <robert.richter@....com>,
	David Miller <davem@...emloft.net>
Subject: Re: [RFC PATCH 2/9] perf: Add ability to dump user regs

On Sun, Oct 17, 2010 at 12:07 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Sat, 2010-10-16 at 00:58 +0200, Frederic Weisbecker wrote:
>> > Yes, PEBS does not capture the entire state.
>> >
>> > Here is what you get on Intel Core:
>> >         u64 flags, ip;
>> >         u64 ax, bx, cx, dx;
>> >         u64 si, di, bp, sp;
>> >         u64 r8,  r9,  r10, r11;
>> >         u64 r12, r13, r14, r15;
>
>> Ok, that seems to cover most of the state. I guess few people care
>> about cs, ds, es, fs, gs, most of the time.
>
> Yeah, except if you want to profile wine or something like that ;-)
>
That means that if you want the segment registers, then you cannot
use PEBS. I think you could catch that when the event is created.

The other problem here is how to name registers at the API level.
You would be introducing architecture-specific register names
in perf_event.h. There is no such a thing today.
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