1. 14 Aug, 2020 1 commit
  2. 11 Aug, 2020 1 commit
    • Rafael J. Wysocki's avatar
      cpufreq: intel_pstate: Implement passive mode with HWP enabled · f6ebbcf0
      Rafael J. Wysocki authored
      Allow intel_pstate to work in the passive mode with HWP enabled and
      make it set the HWP minimum performance limit (HWP floor) to the
      P-state value given by the target frequency supplied by the cpufreq
      governor, so as to prevent the HWP algorithm and the CPU scheduler
      from working against each other, at least when the schedutil governor
      is in use, and update the intel_pstate documentation accordingly.
      
      Among other things, this allows utilization clamps to be taken
      into account, at least to a certain extent, when intel_pstate is
      in use and makes it more likely that sufficient capacity for
      deadline tasks will be provided.
      
      After this change, the resulting behavior of an HWP system with
      intel_pstate in the passive mode should be close to the behavior
      of the analogous non-HWP system with intel_pstate in the passive
      mode, except that the HWP algorithm is generally allowed to make the
      CPU run at a frequency above the floor P-state set by intel_pstate in
      the entire available range of P-states, while without HWP a CPU can
      run in a P-state above the requested one if the latter falls into the
      range of turbo P-states (referred to as the turbo range) or if the
      P-states of all CPUs in one package are coordinated with each other
      at the hardware level.
      
      [Note that in principle the HWP floor may not be taken into account
       by the processor if it falls into the turbo range, in which case the
       processor has a license to choose any P-state, either below or above
       the HWP floor, just like a non-HWP processor in the case when the
       target P-state falls into the turbo range.]
      
      With this change applied, intel_pstate in the passive mode assumes
      complete control over the HWP request MSR and concurrent changes of
      that MSR (eg. via the direct MSR access interface) are overridden by
      it.
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      Acked-by: default avatarSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
      Reviewed-by: default avatarFrancisco Jerez <currojerez@riseup.net>
      f6ebbcf0
  3. 07 Aug, 2020 38 commits