Messages in this thread Patch in this message | | | From | "Doug Smythies" <> | Subject | RE: [PATCH v2 2/2] cpufreq: intel_pstate: Allow raw energy performance preference value | Date | Wed, 24 Jun 2020 08:37:23 -0700 |
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Hi Srinivas,
I have immediate need for this. I have been using a tool I wrote myself for this which I can now retire. (it wasn't very good anyway). Yours remembers for each governor, and is way better. Thanks.
On 2020.06.23 11:27 Srinivas Pandruvada wrote:
> Currently using attribute "energy_performance_preference", user space can > write one of the four per-defined preference string. These preference > strings gets mapped to a hard-coded Energy-Performance Preference (EPP) or > Energy-Performance Bias (EPB) knob. > > These four values supposed to cover broad spectrum of use cases, but they > are not uniformly distributed in the range.
Suggest:
These four values are supposed to cover broad spectrum of use cases, but are not uniformly distributed in the range.
> There are number of cases, > where this is not enough. For example: > > Suppose user wants more performance when connected to AC. Instead of using > default "balance performance", the "performance" setting can be used. This > changes EPP value from 0x80 to 0x00. But setting EPP to 0, results in > electrical and thermal issues on some platforms.
> This results in CPU to do > aggressive throttling, which causes drop in performance.
Suggest:
This results in aggressive throttling, which causes a drop in performance.
And:
Tough. I consider "performance mode" as sacrosanct, and have always expected these to behave identically and at max CPU freq:
intel_pstate no-hwp / performance intel_cpufreq no-hwp / performance (a.k.a. passive) acpi_cpufreq / performance intel_pstate hwp / performance intel_cpufreq hwp / performance (in future)
as was always the case on my i7-2600K (no hwp) based computer and is not the case on my i5-9600K (hwp capable) computer.
> But some value > between 0x80 and 0x00 results in better performance. But that value can't > be fixed as the power curve is not linear. In some cases just changing EPP > from 0x80 to 0x75 is enough to get significant performance gain. > > Similarly on battery EPP 0x80 can be very aggressive in power consumption. > But picking up the next choice "balance power" results in too much loss > of performance, which cause bad user experience in use case like "Google > Hangout". It was observed that some value between these two EPP is > optimal. > > This change allows fine grain EPP tuning for platform like Chromebooks. > Here based on the product and use cases, different EPP values can be set. > This change is similar to the change done for: > /sys/devices/system/cpu/cpu*/power/energy_perf_bias > where user has choice to write a predefined string or raw value. > > The change itself is trivial. When user preference doesn't match > predefined string preferences and value is an unsigned integer and in > range, use that value for EPP. When the EPP feature is not prsent ^^^^^^ s/prsent/present
> writing raw value is not supported. > > Suggested-by: Len Brown <lenb@kernel.org> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> > --- > Documentation/admin-guide/pm/intel_pstate.rst | 6 ++- > drivers/cpufreq/intel_pstate.c | 50 +++++++++++++++---- > 2 files changed, 45 insertions(+), 11 deletions(-) > > diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin- > guide/pm/intel_pstate.rst > index 939bfdc53f4f..5e209926e0ed 100644 > --- a/Documentation/admin-guide/pm/intel_pstate.rst > +++ b/Documentation/admin-guide/pm/intel_pstate.rst > @@ -561,7 +561,11 @@ somewhere between the two extremes: > Strings written to the ``energy_performance_preference`` attribute are > internally translated to integer values written to the processor's > Energy-Performance Preference (EPP) knob (if supported) or its > -Energy-Performance Bias (EPB) knob. > +Energy-Performance Bias (EPB) knob. It is also possible to write a positive > +integer value between 0 to 255, if the EPP feature is present. If the EPP > +feature is not present, writing integer value to this attribute is not > +supported. In this case, user can use > + "/sys/devices/system/cpu/cpu*/power/energy_perf_bias" interface. > > [Note that tasks may by migrated from one CPU to another by the scheduler's > load-balancing algorithm and if different energy vs performance hints are > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index 1cf6d06f2314..d8f195c7a428 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -602,11 +602,12 @@ static const unsigned int epp_values[] = { > HWP_EPP_POWERSAVE > }; > > -static int intel_pstate_get_energy_pref_index(struct cpudata *cpu_data) > +static int intel_pstate_get_energy_pref_index(struct cpudata *cpu_data, int *raw_epp) > { > s16 epp; > int index = -EINVAL; > > + *raw_epp = 0; > epp = intel_pstate_get_epp(cpu_data, 0); > if (epp < 0) > return epp; > @@ -614,12 +615,14 @@ static int intel_pstate_get_energy_pref_index(struct cpudata *cpu_data) > if (boot_cpu_has(X86_FEATURE_HWP_EPP)) { > if (epp == HWP_EPP_PERFORMANCE) > return 1; > - if (epp <= HWP_EPP_BALANCE_PERFORMANCE) > + if (epp == HWP_EPP_BALANCE_PERFORMANCE) > return 2; > - if (epp <= HWP_EPP_BALANCE_POWERSAVE) > + if (epp == HWP_EPP_BALANCE_POWERSAVE) > return 3; > - else > + if (epp == HWP_EPP_POWERSAVE) > return 4; > + *raw_epp = epp; > + return 0; > } else if (boot_cpu_has(X86_FEATURE_EPB)) { > /* > * Range: > @@ -638,7 +641,8 @@ static int intel_pstate_get_energy_pref_index(struct cpudata *cpu_data) > } > > static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data, > - int pref_index) > + int pref_index, bool use_raw, > + u32 raw_epp) > { > int epp = -EINVAL; > int ret; > @@ -657,6 +661,16 @@ static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data, > > value &= ~GENMASK_ULL(31, 24); > > + if (use_raw) { > + if (raw_epp > 255) { > + ret = -EINVAL; > + goto return_pref; > + } > + value |= (u64)raw_epp << 24; > + ret = wrmsrl_on_cpu(cpu_data->cpu, MSR_HWP_REQUEST, value); > + goto return_pref; > + } > + > if (epp == -EINVAL) > epp = epp_values[pref_index - 1]; > > @@ -694,6 +708,8 @@ static ssize_t store_energy_performance_preference( > { > struct cpudata *cpu_data = all_cpu_data[policy->cpu]; > char str_preference[21]; > + bool raw = false; > + u32 epp; > int ret; > > ret = sscanf(buf, "%20s", str_preference); > @@ -701,10 +717,21 @@ static ssize_t store_energy_performance_preference( > return -EINVAL; > > ret = match_string(energy_perf_strings, -1, str_preference); > - if (ret < 0) > + if (ret < 0) { > + if (!boot_cpu_has(X86_FEATURE_HWP_EPP)) > + return ret; > + > + ret = kstrtouint(buf, 10, &epp); > + if (ret) > + return ret; > + > + raw = true; > + } > + > + ret = intel_pstate_set_energy_pref_index(cpu_data, ret, raw, epp); > + if (ret) > return ret; > > - intel_pstate_set_energy_pref_index(cpu_data, ret); > return count; > } > > @@ -712,13 +739,16 @@ static ssize_t show_energy_performance_preference( > struct cpufreq_policy *policy, char *buf) > { > struct cpudata *cpu_data = all_cpu_data[policy->cpu]; > - int preference; > + int preference, raw_epp; > > - preference = intel_pstate_get_energy_pref_index(cpu_data); > + preference = intel_pstate_get_energy_pref_index(cpu_data, &raw_epp); > if (preference < 0) > return preference; > > - return sprintf(buf, "%s\n", energy_perf_strings[preference]); > + if (raw_epp) > + return sprintf(buf, "%d\n", raw_epp); > + else > + return sprintf(buf, "%s\n", energy_perf_strings[preference]); > } > > cpufreq_freq_attr_rw(energy_performance_preference); > -- > 2.25.4
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