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From: "Bryan O'Sullivan" <bos@serpentine.com>
To: Andi Kleen <ak@muc.de>
Cc: Mikael Pettersson <mikpe@csd.uu.se>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][3/7] perfctr-2.7.2 for 2.6.6-mm2: x86_64
Date: Fri, 14 May 2004 22:37:36 -0700	[thread overview]
Message-ID: <1084599456.4895.103.camel@obsidian.pathscale.com> (raw)
In-Reply-To: <m3oeorvy58.fsf@averell.firstfloor.org>

On Fri, 2004-05-14 at 08:14, Andi Kleen wrote:

> Before merging all that I would definitely recommend some generic
> module to allocate performance counters. IBM had a patch for this
> long ago, and it is even more needed now.

That's currently handled in user space, by PAPI (which sits on top of
perfctr).  One reason *not* to do it in the kernel is the bloat it would
entail; just look at the horrendous mess that is the P4 performance
counter event selector.

> Why do you check for K8 C stepping? I don't see any code that
> does anything special with that.

The reason it's interesting at all is that it's the first K8 stepping
that introduces new performance counter unit masks.  The kernel driver
already passes its notion of what the CPU type is up to userspace. 
(Clearly, userspace could figure this out, since it's just parsing the
cpuid instruction.)

It also checks the CPU type in a few places internally; it just doesn't
happen to care internally about K8 stepping C.  Thoroughness?

	<b


  reply	other threads:[~2004-05-15  5:39 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1VLRr-38z-19@gated-at.bofh.it>
2004-05-14 15:14 ` Andi Kleen
2004-05-15  5:37   ` Bryan O'Sullivan [this message]
2004-05-15  9:09     ` Andi Kleen
2004-05-16  4:15       ` Bryan O'Sullivan
2004-05-16  9:58 Mikael Pettersson
  -- strict thread matches above, loose matches on Subject: below --
2004-05-15 14:44 Mikael Pettersson
2004-05-15 19:26 ` Andi Kleen
2004-05-15 14:42 Mikael Pettersson
2004-05-15 19:16 ` Andi Kleen
2004-05-15 20:40   ` John Reiser
2004-05-15 20:49     ` Andi Kleen
2004-05-14 14:11 Mikael Pettersson

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