From: Andi Kleen <andi@firstfloor.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>, Andi Kleen <andi@firstfloor.org>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86, perf: Use INST_RETIRED.PREC_DIST for cycles:pp on Skylake
Date: Wed, 21 Oct 2015 18:55:42 +0200 [thread overview]
Message-ID: <20151021165542.GN3533@two.firstfloor.org> (raw)
In-Reply-To: <20151021165252.GJ3604@twins.programming.kicks-ass.net>
On Wed, Oct 21, 2015 at 06:52:52PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 21, 2015 at 08:26:08AM -0700, Andi Kleen wrote:
> > So it turns out that UOPS_RETIRED.ALL+pebs only works by accident
> > on Skylake. It's not in the specification.
>
> Accident or not, it works and you've tested it. Might as well keep it.
> Specs can be updated.
No, it's better not to use it.
> Also, even with the SNB 'hickup' they still haven't got the memo that
> cycles is important for PEBS ?
INST_RETIRED.PREC_DIST is a far better cycles than UOPS_RETIRED.ALL
(see my earlier example)
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2015-10-21 16:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-19 22:58 [PATCH] x86, perf: Use INST_RETIRED.PREC_DIST for cycles:pp on Skylake Andi Kleen
2015-10-20 11:36 ` Peter Zijlstra
2015-10-20 22:28 ` Andi Kleen
2015-10-21 8:09 ` Peter Zijlstra
2015-10-21 15:26 ` Andi Kleen
2015-10-21 16:52 ` Peter Zijlstra
2015-10-21 16:55 ` Andi Kleen [this message]
2015-10-21 18:57 ` Peter Zijlstra
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