From: Peter Zijlstra <peterz@infradead.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Andy Lutomirski <luto@amacapital.net>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
Stephane Eranian <eranian@google.com>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH V2] perf: x86: Improve accuracy of perf/sched clock
Date: Mon, 17 Aug 2015 11:56:17 +0200 [thread overview]
Message-ID: <20150817095617.GA20948@worktop> (raw)
In-Reply-To: <55D18E6B.1040402@intel.com>
On Mon, Aug 17, 2015 at 10:34:03AM +0300, Adrian Hunter wrote:
> On 29/07/15 00:14, Adrian Hunter wrote:
> > When TSC is stable perf/sched clock is based on it.
> > However the conversion from cycles to nanoseconds
> > is not as accurate as it could be. Because
> > CYC2NS_SCALE_FACTOR is 10, the accuracy is +/- 1/2048
> >
> > The change is to calculate the maximum shift that
> > results in a multiplier that is still a 32-bit number.
> > For example all frequencies over 1 GHz will have
> > a shift of 32, making the accuracy of the conversion
> > +/- 1/(2^33)
> >
> > Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>
> Is this OK?
Yes I think so, sorry I got backlogged with preparation for Seattle.
Thomas, if you see this, could you merge with my ACK on, otherwise I'll
queue it the normal route once I'm back.
next prev parent reply other threads:[~2015-08-17 9:56 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-28 21:14 [PATCH V2] perf: x86: Improve accuracy of perf/sched clock Adrian Hunter
2015-08-17 7:34 ` Adrian Hunter
2015-08-17 9:56 ` Peter Zijlstra [this message]
2015-08-20 19:31 ` Thomas Gleixner
2015-08-21 6:46 ` Adrian Hunter
2015-08-21 9:05 ` [PATCH V3] " Adrian Hunter
2015-09-01 8:36 ` Adrian Hunter
2015-09-01 8:57 ` Peter Zijlstra
2015-09-13 11:08 ` [tip:perf/core] perf/x86: " tip-bot for Adrian Hunter
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