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From:   "Ghannam, Yazen" <Yazen.Ghannam@amd.com>
To:     "Ghannam, Yazen" <Yazen.Ghannam@amd.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "len.brown@intel.com" <len.brown@intel.com>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Len Brown <lenb@kernel.org>
Subject: RE: [PATCH] tools/power turbostat: Make interval calculation per
 thread to reduce jitter
Thread-Topic: [PATCH] tools/power turbostat: Make interval calculation per
 thread to reduce jitter
Thread-Index: AQHU4zDAw6kMdRt2pEeSvDZqbzvAVaZKM7PQ
Date:   Tue, 23 Apr 2019 17:53:02 +0000
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References: <20190325173232.216357-1-Yazen.Ghannam@amd.com>
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> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org <linux-kernel-owner@vger.kernel.=
org> On Behalf Of Ghannam, Yazen
> Sent: Monday, March 25, 2019 12:33 PM
> To: linux-pm@vger.kernel.org
> Cc: Ghannam, Yazen <Yazen.Ghannam@amd.com>; linux-kernel@vger.kernel.org;=
 lenb@kernel.org
> Subject: [PATCH] tools/power turbostat: Make interval calculation per thr=
ead to reduce jitter
>=20
> From: Yazen Ghannam <yazen.ghannam@amd.com>
>=20
> 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.
>=20
> 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.
>=20
> Define a per thread time value to hold the delta between samples taken
> on the thread.
>=20
> Use the timestamp taken at the beginning of sampling to calculate the
> delta.
>=20
> Move the thread's beginning timestamp to after the CPU migration to
> avoid jitter due to the migration.
>=20
> Use the global time delta for the average time delta.
>=20
> Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> ---

Hi Len,

Any comments on this patch?

Thanks,
Yazen