linux-kernel - RE: [PATCH] tools/power turbostat: Make interval calculation per thread to reduce jitter

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Date:   Fri, 7 Jun 2019 16:28:07 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "len.brown@...el.com" <len.brown@...el.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Len Brown <lenb@...nel.org>
Subject: RE: [PATCH] tools/power turbostat: Make interval calculation per
 thread to reduce jitter

> -----Original Message-----
> From: Ghannam, Yazen <Yazen.Ghannam@....com>
> Sent: Tuesday, April 23, 2019 12:53 PM
> To: Ghannam, Yazen <Yazen.Ghannam@....com>; linux-pm@...r.kernel.org; len.brown@...el.com
> Cc: linux-kernel@...r.kernel.org; Len Brown <lenb@...nel.org>
> Subject: RE: [PATCH] tools/power turbostat: Make interval calculation per thread to reduce jitter
> 
> > -----Original Message-----
> > From: linux-kernel-owner@...r.kernel.org <linux-kernel-owner@...r.kernel.org> On Behalf Of Ghannam, Yazen
> > Sent: Monday, March 25, 2019 12:33 PM
> > To: linux-pm@...r.kernel.org
> > Cc: Ghannam, Yazen <Yazen.Ghannam@....com>; linux-kernel@...r.kernel.org; lenb@...nel.org
> > Subject: [PATCH] tools/power turbostat: Make interval calculation per thread to reduce jitter
> >
> > From: Yazen Ghannam <yazen.ghannam@....com>
> >
> > Turbostat currently normalizes TSC and other values by dividing by an
> > interval. This interval is the delta between the start of one global
> > (all counters on all CPUs) sampling and the start of another. However,
> > this introduces a lot of jitter into the data.
> >
> > In order to reduce jitter, the interval calculation should be based on
> > timestamps taken per thread and close to the start of the thread's
> > sampling.
> >
> > Define a per thread time value to hold the delta between samples taken
> > on the thread.
> >
> > Use the timestamp taken at the beginning of sampling to calculate the
> > delta.
> >
> > Move the thread's beginning timestamp to after the CPU migration to
> > avoid jitter due to the migration.
> >
> > Use the global time delta for the average time delta.
> >
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
> > ---
> 
> Hi Len,
> 
> Any comments on this patch?
> 

Hi Len,

Just wanted to check in. Do you have any comments on this patch?

Thanks,
Yazen