Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state selection algorithm for Core

From	Wanpeng Li <kernellwp@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state selection algorithm for Core
Date	2016-08-23 05:50 +0200
Message-ID	<s9aSR-6Y5-1@gated-at.bofh.it> (permalink)
References	<s18Ex-6NS-1@gated-at.bofh.it> <s18Ex-6NS-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

Hi Rafael,
2016-08-01 7:38 GMT+08:00 Rafael J. Wysocki <rjw@rjwysocki.net>:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> The PID-base P-state selection algorithm used by intel_pstate for
> Core processors is based on very weak foundations.  Namely, its
> decisions are mostly based on the values of the APERF and MPERF
> feedback registers and it only estimates the actual utilization to
> check if it is not extremely low (in order to avoid getting stuck
> in the highest P-state in that case).
>
> Since it generally causes the CPU P-state to ramp up quickly, it
> leads to satisfactory performance, but the metric used by it is only
> really valid when the CPU changes P-states by itself (ie. in the turbo
> range) and if the P-state value set by the driver is treated by the
> CPU as the upper limit on turbo P-states selected by it.

Do you mean CPU will ignore the request value which is submitted by
intel_pstate driver in the turbo range, but respect the upper limit on
the turbo P-states which is submitted by intel_pstate driver?

Regards,
Wanpeng Li

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state selection  algorithm for Core Wanpeng Li <kernellwp@gmail.com> - 2016-08-23 05:50 +0200
  Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state  selection algorithm for Core Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> - 2016-08-23 06:10 +0200
    Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state selection  algorithm for Core Wanpeng Li <kernellwp@gmail.com> - 2016-08-23 07:00 +0200
      Re: [RFC][PATCH 7/7] cpufreq: intel_pstate: Change P-state selection algorithm for Core "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-08-23 19:30 +0200

csiph-web