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From: Ingo Molnar <mingo@elte.hu>
To: Andi Kleen <andi@firstfloor.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Lin Ming <ming.m.lin@intel.com>,
	Stephane Eranian <eranian@google.com>,
	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] perf, x86: Add Intel Nehalem/Westmere uncore pmu
Date: Wed, 6 Jul 2011 11:35:01 +0200	[thread overview]
Message-ID: <20110706093501.GA11969@elte.hu> (raw)
In-Reply-To: <cf54fbb6e05ab86a5c6029eda70012e4.squirrel@www.firstfloor.org>


* Andi Kleen <andi@firstfloor.org> wrote:

> 
> >
> >>   But it's not strictly required I would say,
> >> 44(?) bits are probably enough for near all use cases.
> >
> > 44bits is in the hours range for pure cycle counts, which is 
> > so-so. I bet you're going to be very annoyed when you find your 
> > counters are wrecked after your 5 hour test run finishes.
> 
> For these kinds of long running measurements you usually care about 
> ratios, not absolutes. Some infrequent wrapping should not 
> substantially change. those.

That's just empty blathering - those who *do* take a look at 
long-running absolute values obviously care.

There's absolutely no reason to be sloppy here - this needs to be 
implemented correctly.

Thanks,

	Ingo

  reply	other threads:[~2011-07-06  9:35 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-30  8:09 [PATCH 0/4] perf: Intel uncore pmu counting support Lin Ming
2011-06-30  8:09 ` [PATCH 1/4] perf, x86: Add Intel Nehalem/Westmere uncore pmu Lin Ming
2011-06-30 14:08   ` Peter Zijlstra
2011-07-01  6:05     ` Lin Ming
2011-06-30 16:58   ` Andi Kleen
2011-07-04  6:39     ` Lin Ming
2011-07-04  8:38       ` Peter Zijlstra
2011-07-04 21:57       ` Andi Kleen
2011-07-05 11:22         ` Peter Zijlstra
2011-07-05 12:48           ` Lin Ming
2011-07-05 12:56             ` Peter Zijlstra
2011-07-05 13:13               ` Lin Ming
2011-07-05 16:01           ` Andi Kleen
2011-07-06  9:35             ` Ingo Molnar [this message]
2011-06-30  8:09 ` [PATCH 2/4] perf, x86: Add Intel SandyBridge " Lin Ming
2011-06-30 22:09   ` Peter Zijlstra
2011-06-30  8:09 ` [PATCH 3/4] perf: Remove perf_event_attr::type check Lin Ming
2011-07-21 19:31   ` [tip:perf/core] " tip-bot for Lin Ming
2011-06-30  8:09 ` [PATCH 4/4] perf tool: Get PMU type id from sysfs Lin Ming
2011-06-30 12:10 ` [PATCH 0/4] perf: Intel uncore pmu counting support Stephane Eranian
2011-06-30 14:10   ` Peter Zijlstra
2011-06-30 16:27   ` Stephane Eranian
2011-07-01  3:17     ` Lin Ming
2011-07-01 10:49       ` Stephane Eranian
2011-07-01 12:23         ` Stephane Eranian
2011-07-01 12:28           ` Stephane Eranian
2011-07-04  6:03         ` Lin Ming
2011-07-01  5:49   ` Lin Ming
2011-07-01 11:08 ` Ingo Molnar

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