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

[Ghannam, Yazen]

> -----Original Message-----
> From: linux-kernel-owner@xxxxxxxxxxxxxxx <linux-kernel-owner@xxxxxxxxxxxxxxx> On Behalf Of Ghannam, Yazen
> Sent: Monday, March 25, 2019 12:33 PM
> To: linux-pm@xxxxxxxxxxxxxxx
> Cc: Ghannam, Yazen <Yazen.Ghannam@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; lenb@xxxxxxxxxx
> Subject: [PATCH] tools/power turbostat: Make interval calculation per thread to reduce jitter
> 
> From: Yazen Ghannam <yazen.ghannam@xxxxxxx>
> 
> 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@xxxxxxx>
> ---

Hi Len,

Any comments on this patch?

Thanks,
Yazen