"Pandruvada, Srinivas" writes: > On Wed, 2020-03-18 at 12:51 -0700, Francisco Jerez wrote: >> "Pandruvada, Srinivas" writes: >> >> > On Tue, 2020-03-10 at 14:42 -0700, Francisco Jerez wrote: >> > > This implements a simple variably low-pass-filtering governor in >> > > control of the HWP MIN/MAX PERF range based on the previously >> > > introduced get_vlp_target_range(). See "cpufreq: intel_pstate: >> > > Implement VLP controller target P-state range estimation." for >> > > the >> > > rationale. >> > >> > I just gave a try on a pretty idle system with just systemd >> > processes >> > and usual background tasks with nomodset. >> > >> > I see that there HWP min is getting changed between 4-8. Why are >> > changing HWP dynamic range even on an idle system running no where >> > close to TDP? >> > >> >> The HWP request range is clamped to the frequency range specified by >> the >> CPUFREQ policy and to the cpu->pstate.min_pstate bound. >> >> If you see the HWP minimum fluctuating above that it's likely a sign >> of >> your system not being completely idle -- If that's the case it's >> likely >> to go away after you do: >> >> echo 0 > /sys/kernel/debug/pstate_snb/vlp_realtime_gain_pml >> > The objective which I though was to improve performance of GPU > workloads limited by TDP because of P-states ramping up and resulting > in less power to GPU to complete a task. > > HWP takes decision not on just load on a CPU but several other factors > like total SoC power and scalability. We don't want to disturb HWP > algorithms when there is no TDP limitations. If writing 0, causes this > behavior then that should be the default. > The heuristic disabled by that debugfs file is there to avoid regressions in latency-sensitive workloads as you can probably get from the ecomments. However ISTR those regressions were specific to non-HWP systems, so I wouldn't mind disabling it for the moment (or punting it to the non-HWP series if you like)j. But first I need to verify that there are no performance regressions on HWP systems after changing that. Can you confirm that the debugfs write above prevents the behavior you'd like to avoid? > Thanks, > Srinivas > > > > > >> > Thanks, >> > Srinivas >> > >> > >> > > Signed-off-by: Francisco Jerez >> > > --- >> > > drivers/cpufreq/intel_pstate.c | 79 >> > > +++++++++++++++++++++++++++++++++- >> > > 1 file changed, 77 insertions(+), 2 deletions(-) >> > > >> > > diff --git a/drivers/cpufreq/intel_pstate.c >> > > b/drivers/cpufreq/intel_pstate.c >> > > index cecadfec8bc1..a01eed40d897 100644 >> > > --- a/drivers/cpufreq/intel_pstate.c >> > > +++ b/drivers/cpufreq/intel_pstate.c >> > > @@ -1905,6 +1905,20 @@ static void intel_pstate_reset_vlp(struct >> > > cpudata *cpu) >> > > vlp->gain = max(1, div_fp(1000, vlp_params.setpoint_0_pml)); >> > > vlp->target.p_base = 0; >> > > vlp->stats.last_response_frequency_hz = vlp_params.avg_hz; >> > > + >> > > + if (hwp_active) { >> > > + const uint32_t p0 = max(cpu->pstate.min_pstate, >> > > + cpu->min_perf_ratio); >> > > + const uint32_t p1 = max_t(uint32_t, p0, cpu- >> > > > max_perf_ratio); >> > > + const uint64_t hwp_req = (READ_ONCE(cpu- >> > > > hwp_req_cached) & >> > > + ~(HWP_MAX_PERF(~0L) | >> > > + HWP_MIN_PERF(~0L) | >> > > + HWP_DESIRED_PERF(~0L))) | >> > > + HWP_MIN_PERF(p0) | >> > > HWP_MAX_PERF(p1); >> > > + >> > > + wrmsrl_on_cpu(cpu->cpu, MSR_HWP_REQUEST, hwp_req); >> > > + cpu->hwp_req_cached = hwp_req; >> > > + } >> > > } >> > > >> > > /** >> > > @@ -2222,6 +2236,46 @@ static void >> > > intel_pstate_adjust_pstate(struct >> > > cpudata *cpu) >> > > fp_toint(cpu->iowait_boost * 100)); >> > > } >> > > >> > > +static void intel_pstate_adjust_pstate_range(struct cpudata >> > > *cpu, >> > > + const unsigned int >> > > range[]) >> > > +{ >> > > + const int from = cpu->hwp_req_cached; >> > > + unsigned int p0, p1, p_min, p_max; >> > > + struct sample *sample; >> > > + uint64_t hwp_req; >> > > + >> > > + update_turbo_state(); >> > > + >> > > + p0 = max(cpu->pstate.min_pstate, cpu->min_perf_ratio); >> > > + p1 = max_t(unsigned int, p0, cpu->max_perf_ratio); >> > > + p_min = clamp_t(unsigned int, range[0], p0, p1); >> > > + p_max = clamp_t(unsigned int, range[1], p0, p1); >> > > + >> > > + trace_cpu_frequency(p_max * cpu->pstate.scaling, cpu->cpu); >> > > + >> > > + hwp_req = (READ_ONCE(cpu->hwp_req_cached) & >> > > + ~(HWP_MAX_PERF(~0L) | HWP_MIN_PERF(~0L) | >> > > + HWP_DESIRED_PERF(~0L))) | >> > > + HWP_MIN_PERF(vlp_params.debug & 2 ? p0 : p_min) | >> > > + HWP_MAX_PERF(vlp_params.debug & 4 ? p1 : p_max); >> > > + >> > > + if (hwp_req != cpu->hwp_req_cached) { >> > > + wrmsrl(MSR_HWP_REQUEST, hwp_req); >> > > + cpu->hwp_req_cached = hwp_req; >> > > + } >> > > + >> > > + sample = &cpu->sample; >> > > + trace_pstate_sample(mul_ext_fp(100, sample->core_avg_perf), >> > > + fp_toint(sample->busy_scaled), >> > > + from, >> > > + hwp_req, >> > > + sample->mperf, >> > > + sample->aperf, >> > > + sample->tsc, >> > > + get_avg_frequency(cpu), >> > > + fp_toint(cpu->iowait_boost * 100)); >> > > +} >> > > + >> > > static void intel_pstate_update_util(struct update_util_data >> > > *data, >> > > u64 time, >> > > unsigned int flags) >> > > { >> > > @@ -2260,6 +2314,22 @@ static void >> > > intel_pstate_update_util(struct >> > > update_util_data *data, u64 time, >> > > intel_pstate_adjust_pstate(cpu); >> > > } >> > > >> > > +/** >> > > + * Implementation of the cpufreq update_util hook based on the >> > > VLP >> > > + * controller (see get_vlp_target_range()). >> > > + */ >> > > +static void intel_pstate_update_util_hwp_vlp(struct >> > > update_util_data >> > > *data, >> > > + u64 time, unsigned int >> > > flags) >> > > +{ >> > > + struct cpudata *cpu = container_of(data, struct cpudata, >> > > update_util); >> > > + >> > > + if (update_vlp_sample(cpu, time, flags)) { >> > > + const struct vlp_target_range *target = >> > > + get_vlp_target_range(cpu); >> > > + intel_pstate_adjust_pstate_range(cpu, target->value); >> > > + } >> > > +} >> > > + >> > > static struct pstate_funcs core_funcs = { >> > > .get_max = core_get_max_pstate, >> > > .get_max_physical = core_get_max_pstate_physical, >> > > @@ -2389,6 +2459,9 @@ static int intel_pstate_init_cpu(unsigned >> > > int >> > > cpunum) >> > > >> > > intel_pstate_get_cpu_pstates(cpu); >> > > >> > > + if (pstate_funcs.update_util == >> > > intel_pstate_update_util_hwp_vlp) >> > > + intel_pstate_reset_vlp(cpu); >> > > + >> > > pr_debug("controlling: cpu %d\n", cpunum); >> > > >> > > return 0; >> > > @@ -2398,7 +2471,8 @@ static void >> > > intel_pstate_set_update_util_hook(unsigned int cpu_num) >> > > { >> > > struct cpudata *cpu = all_cpu_data[cpu_num]; >> > > >> > > - if (hwp_active && !hwp_boost) >> > > + if (hwp_active && !hwp_boost && >> > > + pstate_funcs.update_util != >> > > intel_pstate_update_util_hwp_vlp) >> > > return; >> > > >> > > if (cpu->update_util_set) >> > > @@ -2526,7 +2600,8 @@ static int intel_pstate_set_policy(struct >> > > cpufreq_policy *policy) >> > > * was turned off, in that case we need to clear the >> > > * update util hook. >> > > */ >> > > - if (!hwp_boost) >> > > + if (!hwp_boost && pstate_funcs.update_util != >> > > + intel_pstate_update_util_hwp_vlp) >> > > intel_pstate_clear_update_util_hook(policy- >> > > > cpu); >> > > intel_pstate_hwp_set(policy->cpu); >> > > }