linux-kernel - Re: ptrace API extensions for BTS

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Message-ID: <7c86c4470801300539g3c6e2cacxfafb69e81c7ffe7d@mail.gmail.com>
Date:	Wed, 30 Jan 2008 14:39:29 +0100
From:	"stephane eranian" <eranian@...glemail.com>
To:	"Metzger, Markus T" <markus.t.metzger@...el.com>
Cc:	"Roland McGrath" <roland@...hat.com>,
	"Ingo Molnar" <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	markus.t.metzger@...il.com
Subject: Re: ptrace API extensions for BTS

Markus,

On Jan 30, 2008 1:52 PM, Metzger, Markus T <markus.t.metzger@...el.com> wrote:
> >From: stephane eranian [mailto:eranian@...glemail.com]
> >Sent: Mittwoch, 30. Januar 2008 12:01
>
> >You can get information about the perfmon2 project at:
> >http://perfmon2.sf.net
>
> I downloaded your patch for 2.6.23 and cloned your git repository.
>
> From a first glance, it looks like there is indeed a lot of overlap.
>
>
> >I would like to take a look at your patches. Where can I get them?
>
> You can find the changes in the mm branch of the x86 git. Do they keep
> the patches there, somewhere, as well?

I will take a look at what you have in -mm git.

>
> You should get the best overview if you look at arch/x86/kernel/ds.c,
> include/asm-x86/ds.h, include/asm-x86/ptrace-abi.h, and
> arch/x86/kernel/ptrace.c or simply grep for BTS.
>
OK.

>
> >My understanding at this point is that we would need to coordinate
> >access to the
> >DS_AREA. It would likely have to be mutually exclusive access.
>
> From a brief look at your patch, I would say that we should rather
> combine the configuration and collection part. They are very similar.
>
That's probably fine too. I'll let you know once I know more about your code.

> We might still want to provide different interfaces on top of it.
> In particular, I think the ptrace interface is most appropriate for
> debuggers.

I agree.

> >Now, there is some preliminary perf. MSR allocator in the kernel.
> >However, it does not know
> >of all available MSRs out there. It focuses on the counters mostly.
> >Perfmon, oprofile and
> >the NMI watchdog use it. I think it could be generalized to other MSR
> >(non-contiguous).
> >
> >I would be happy to work with you in refining this MSR allocator.
>
>
> Are you planning to get the perfmon patch into the kernel? Or do you
> want it to remain a separate patch?

The former, i.e., trying to merge with mainline.

>
> In the first case, we should try to merge the features. In the second
> case, refining the MSR allocator would probably be best.
>
>
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