| Message ID | 2781262.mvXUDI8C0e@rjwysocki.net |
|---|---|
| State | New |
| Headers | show |
| Series | [v1] cpufreq: intel_pstate: Make it possible to avoid enabling CAS | expand |
On Mon, Jan 27, 2025 at 3:07 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Capacity-aware scheduling (CAS) is enabled by default by intel_pstate on > hybrid systems without SMT, but in some usage scenarios it may be more > attractive to place tasks for maximum CPU performance regardless of the > extra cost in terms of energy, which is the case on such systems when > CAS is not enabled, so introduce a command line option to forbid > intel_pstate to enable CAS. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Srinivas, Any concerns or comments? > --- > Documentation/admin-guide/kernel-parameters.txt | 3 +++ > Documentation/admin-guide/pm/intel_pstate.rst | 3 +++ > drivers/cpufreq/intel_pstate.c | 9 +++++++++ > 3 files changed, 15 insertions(+) > > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -2295,6 +2295,9 @@ > per_cpu_perf_limits > Allow per-logical-CPU P-State performance control limits using > cpufreq sysfs interface > + no_cas > + Do not enable capacity-aware scheduling (CAS) on > + hybrid systems > > intremap= [X86-64,Intel-IOMMU,EARLY] > on enable Interrupt Remapping (default) > --- a/Documentation/admin-guide/pm/intel_pstate.rst > +++ b/Documentation/admin-guide/pm/intel_pstate.rst > @@ -696,6 +696,9 @@ > Use per-logical-CPU P-State limits (see `Coordination of P-state > Limits`_ for details). > > +``no_cas`` > + Do not enable capacity-aware scheduling (CAS) which is enabled by > + default on hybrid systems. > > Diagnostics and Tuning > ====================== > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -936,6 +936,8 @@ > NULL, > }; > > +static bool no_cas __ro_after_init; > + > static struct cpudata *hybrid_max_perf_cpu __read_mostly; > /* > * Protects hybrid_max_perf_cpu, the capacity_perf fields in struct cpudata, > @@ -1041,6 +1043,10 @@ > > static void hybrid_init_cpu_capacity_scaling(bool refresh) > { > + /* Bail out if enabling capacity-aware scheduling is prohibited. */ > + if (no_cas) > + return; > + > /* > * If hybrid_max_perf_cpu is set at this point, the hybrid CPU capacity > * scaling has been enabled already and the driver is just changing the > @@ -3835,6 +3841,9 @@ > if (!strcmp(str, "no_hwp")) > no_hwp = 1; > > + if (!strcmp(str, "no_cas")) > + no_cas = true; > + > if (!strcmp(str, "force")) > force_load = 1; > if (!strcmp(str, "hwp_only")) > > > >
On Fri, 2025-02-07 at 13:55 +0100, Rafael J. Wysocki wrote: > On Mon, Jan 27, 2025 at 3:07 PM Rafael J. Wysocki <rjw@rjwysocki.net> > wrote: > > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > Capacity-aware scheduling (CAS) is enabled by default by > > intel_pstate on > > hybrid systems without SMT, but in some usage scenarios it may be > > more > > attractive to place tasks for maximum CPU performance regardless of > > the > > extra cost in terms of energy, which is the case on such systems > > when > > CAS is not enabled, so introduce a command line option to forbid > > intel_pstate to enable CAS. > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Srinivas, > > Any concerns or comments? > No. Acked-by:Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> > > --- > > Documentation/admin-guide/kernel-parameters.txt | 3 +++ > > Documentation/admin-guide/pm/intel_pstate.rst | 3 +++ > > drivers/cpufreq/intel_pstate.c | 9 +++++++++ > > 3 files changed, 15 insertions(+) > > > > --- a/Documentation/admin-guide/kernel-parameters.txt > > +++ b/Documentation/admin-guide/kernel-parameters.txt > > @@ -2295,6 +2295,9 @@ > > per_cpu_perf_limits > > Allow per-logical-CPU P-State performance > > control limits using > > cpufreq sysfs interface > > + no_cas > > + Do not enable capacity-aware scheduling > > (CAS) on > > + hybrid systems > > > > intremap= [X86-64,Intel-IOMMU,EARLY] > > on enable Interrupt Remapping > > (default) > > --- a/Documentation/admin-guide/pm/intel_pstate.rst > > +++ b/Documentation/admin-guide/pm/intel_pstate.rst > > @@ -696,6 +696,9 @@ > > Use per-logical-CPU P-State limits (see `Coordination of P- > > state > > Limits`_ for details). > > > > +``no_cas`` > > + Do not enable capacity-aware scheduling (CAS) which is > > enabled by > > + default on hybrid systems. > > > > Diagnostics and Tuning > > ====================== > > --- a/drivers/cpufreq/intel_pstate.c > > +++ b/drivers/cpufreq/intel_pstate.c > > @@ -936,6 +936,8 @@ > > NULL, > > }; > > > > +static bool no_cas __ro_after_init; > > + > > static struct cpudata *hybrid_max_perf_cpu __read_mostly; > > /* > > * Protects hybrid_max_perf_cpu, the capacity_perf fields in > > struct cpudata, > > @@ -1041,6 +1043,10 @@ > > > > static void hybrid_init_cpu_capacity_scaling(bool refresh) > > { > > + /* Bail out if enabling capacity-aware scheduling is > > prohibited. */ > > + if (no_cas) > > + return; > > + > > /* > > * If hybrid_max_perf_cpu is set at this point, the hybrid > > CPU capacity > > * scaling has been enabled already and the driver is just > > changing the > > @@ -3835,6 +3841,9 @@ > > if (!strcmp(str, "no_hwp")) > > no_hwp = 1; > > > > + if (!strcmp(str, "no_cas")) > > + no_cas = true; > > + > > if (!strcmp(str, "force")) > > force_load = 1; > > if (!strcmp(str, "hwp_only")) > > > > > > > > >
--- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2295,6 +2295,9 @@ per_cpu_perf_limits Allow per-logical-CPU P-State performance control limits using cpufreq sysfs interface + no_cas + Do not enable capacity-aware scheduling (CAS) on + hybrid systems intremap= [X86-64,Intel-IOMMU,EARLY] on enable Interrupt Remapping (default) --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -696,6 +696,9 @@ Use per-logical-CPU P-State limits (see `Coordination of P-state Limits`_ for details). +``no_cas`` + Do not enable capacity-aware scheduling (CAS) which is enabled by + default on hybrid systems. Diagnostics and Tuning ====================== --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -936,6 +936,8 @@ NULL, }; +static bool no_cas __ro_after_init; + static struct cpudata *hybrid_max_perf_cpu __read_mostly; /* * Protects hybrid_max_perf_cpu, the capacity_perf fields in struct cpudata, @@ -1041,6 +1043,10 @@ static void hybrid_init_cpu_capacity_scaling(bool refresh) { + /* Bail out if enabling capacity-aware scheduling is prohibited. */ + if (no_cas) + return; + /* * If hybrid_max_perf_cpu is set at this point, the hybrid CPU capacity * scaling has been enabled already and the driver is just changing the @@ -3835,6 +3841,9 @@ if (!strcmp(str, "no_hwp")) no_hwp = 1; + if (!strcmp(str, "no_cas")) + no_cas = true; + if (!strcmp(str, "force")) force_load = 1; if (!strcmp(str, "hwp_only"))