Messages in this thread Patch in this message | | | Subject | Re: [PATCH] cpufreq: intel_pstate: Use the latest guaranteed freq during verify | From | Srinivas Pandruvada <> | Date | Thu, 17 Dec 2020 06:19:13 -0800 |
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On Thu, 2020-12-17 at 14:58 +0100, Rafael J. Wysocki wrote: > On Thu, Dec 17, 2020 at 11:44 AM Srinivas Pandruvada > <srinivas.pandruvada@linux.intel.com> wrote: > > > > This change tries to address an issue, when BIOS disabled turbo > > but HWP_CAP guaranteed is changed later and user space wants to > > take > > advantage of this increased guaranteed performance. > > > > The HWP_CAP.GUARANTEED value is not a static value. It can be > > changed > > by some out of band agent or during Intel Speed Select performance > > level change. The HWP_CAP.MAX still shows max possible performance > > when > > BIOS disabled turbo. So guaranteed can still change as long as this > > is > > same or below HWP_CAP.MAX. > > > > When guaranteed is changed, the sysfs base_frequency attributes > > shows > > the latest guaranteed frequency. This attribute can be used by user > > space software to update scaling min/max frequency. > > > > Currently the setpolicy callback already uses the latest HWP_CAP > > values when setting HWP_REQ. But the verify callback will still > > restrict > > the user settings to the to old guaranteed value. So if the > > guaranteed > > is increased, user space can't take advantage of it. > > > > To solve this similar to setpolicy callback, read the latest > > HWP_CAP > > values and use it to restrict the maximum setting. This is done by > > calling intel_pstate_get_hwp_max(), which already accounts for user > > and BIOS turbo disable to get the current max performance. > > > > This issue is side effect of fixing the issue of scaling frequency > > limits by the > > 'commit eacc9c5a927e ("cpufreq: intel_pstate: > > Fix intel_pstate_get_hwp_max() for turbo disabled")' > > The fix resulted in correct setting of reduced scaling frequencies, > > but this resulted in capping HWP.REQ to HWP_CAP.GUARANTEED in this > > case. > > > > Cc: 5.8+ <stable@vger.kernel.org> # 5.8+ > > Signed-off-by: Srinivas Pandruvada < > > srinivas.pandruvada@linux.intel.com> > > --- > > drivers/cpufreq/intel_pstate.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/drivers/cpufreq/intel_pstate.c > > b/drivers/cpufreq/intel_pstate.c > > index 2a4db856222f..7081d1edb22b 100644 > > --- a/drivers/cpufreq/intel_pstate.c > > +++ b/drivers/cpufreq/intel_pstate.c > > @@ -2199,6 +2199,12 @@ static void > > intel_pstate_clear_update_util_hook(unsigned int cpu) > > > > static int intel_pstate_get_max_freq(struct cpudata *cpu) > > { > > + if (hwp_active) { > > + int turbo_max, max_state; > > + > > + intel_pstate_get_hwp_max(cpu->cpu, &turbo_max, > > &max_state); > > This would cause intel_pstate_get_hwp_max() to be called twice in > intel_pstate_update_perf_limits() which is not perfect.
We can optimize by using cached value.
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 7081d1edb22b..d345c9ef240c 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -2223,7 +2223,11 @@ static void intel_pstate_update_perf_limits(struct cpudata *cpu, * rather than pure ratios. */ if (hwp_active) { - intel_pstate_get_hwp_max(cpu->cpu, &turbo_max, &max_state); + if (global.no_turbo || global.turbo_disabled) + max_state = HWP_GUARANTEED_PERF(cpu- >hwp_cap_cached); + else + max_state = HWP_HIGHEST_PERF(cpu- >hwp_cap_cached); + turbo_max = HWP_HIGHEST_PERF(cpu->hwp_cached); } else { max_state = global.no_turbo || global.turbo_disabled ? cpu->pstate.max_pstate : cpu- >pstate.turbo_pstate;
Thanks, Srinivas
> > > + return max_state * cpu->pstate.scaling; > > + } > > return global.turbo_disabled || global.no_turbo ? > > cpu->pstate.max_freq : cpu- > > >pstate.turbo_freq; > > } > > --
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