linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Update Balance performance EPP for Sapphire Rapids

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Date:   Thu, 23 Feb 2023 19:54:11 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     rafael@...nel.org, lenb@...nel.org, viresh.kumar@...aro.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: intel_pstate: Update Balance performance EPP for
 Sapphire Rapids

On Wed, Feb 22, 2023 at 7:45 AM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> While majority of server OS distributions are deployed with performance
> governor as the default, some distributions like Ubuntu uses powersave
> governor as the default.
>
> While the powersave governor has much lower power, the performance is
> lower than +25% for several workloads compared to performance governor.
>
> One report is published by www.Phoronix.com showing difference of 37%.
>
> The goal here is to keep mean performance delta of powersave governor
> from performance governor around 10% to 12% by running wide variety
> of server workloads. For some bursty workload, this delta can be still
> large, as ramp up of frequency will still lag with powersave governor
> irrespective of EPP setting. The performance governor always requests
> maximum frequency.
>
> Based on experiments, EPP of 0x00, 0x10, 0x20, the performance delta for
> powersave governor is around 12%. But the EPP 0x20 has 18% lower average
> power.
>
> Also experimets are done by raising intel_pstate sysfs min_perf_pct as
> high as 50%. This didn't bring in any additional improvements compared
> to just changing EPP.
>
> From the Alder Lake processor generation, intel_pstate driver has
> capability to update EPP for the default balance_performance based
> on the CPU model. Use the same method to update the default
> balance_performance EPP for the Sapphire Rapids processor to 0x20.
>
> Link: https://www.phoronix.com/review/centos-clear-spr/6
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index fd73d6d2b808..32a4004d155d 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -3372,6 +3372,7 @@ static const struct x86_cpu_id intel_epp_balance_perf[] = {
>          * AlderLake Mobile CPUs.
>          */
>         X86_MATCH_INTEL_FAM6_MODEL(ALDERLAKE_L, 102),
> +       X86_MATCH_INTEL_FAM6_MODEL(SAPPHIRERAPIDS_X, 32),
>         {}
>  };
>
> --

Applied as 6.3-rc material with some edits in the subject and changelog.

Thanks!