Re: [RFC/RFT] [PATCH 07/10] cpufreq: intel_pstate: HWP boost performance on busy task migrate

[Rafael J. Wysocki]

On Wed, May 16, 2018 at 6:49 AM, Srinivas Pandruvada
<srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:
> When a busy task migrates to a new CPU boost HWP prformance to max. This
> helps workloads on servers with per core P-states, which saturates all
> CPUs and then they migrate frequently. But changing limits has extra over
> head of issuing new HWP Request MSR, which takes 1000+
> cycles. So this change limits setting HWP Request MSR.
> Rate control in setting HWP Requests:
> - If the current performance is around P1, simply ignore.
> - Once set wait till hold time, till remove boost. While the boost
>  is on, another flags is notified, it will prolong boost.
> - The task migrates needs to have some utilzation which is more
> than threshold utilization, which will trigger P-state above minimum.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
> ---
>  drivers/cpufreq/intel_pstate.c | 37 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index d418265..ec455af 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -227,6 +227,7 @@ struct global_params {
>   *                     defines callback and arguments
>   * @hwp_boost_active:  HWP performance is boosted on this CPU
>   * @last_io_update:    Last time when IO wake flag was set
> + * @migrate_hint:      Set when scheduler indicates thread migration
>   *
>   * This structure stores per CPU instance data for all CPUs.
>   */
> @@ -263,6 +264,7 @@ struct cpudata {
>         call_single_data_t csd;
>         bool hwp_boost_active;
>         u64 last_io_update;
> +       bool migrate_hint;

Why do you need this in the struct?

It looks like it only is used locally in intel_pstate_update_util_hwp().

>  };