On Wed, 2018-05-16 at 17:19 +0200, Juri Lelli wrote: > On 15/05/18 21:49, Srinivas Pandruvada wrote: > > intel_pstate has two operating modes: active and passive. In > > "active" > > mode, the in-built scaling governor is used and in "passive" mode, > > the driver can be used with any governor like "schedutil". In > > "active" > > mode the utilization values from schedutil is not used and there is > > a requirement from high performance computing use cases, not to > > read > > any APERF/MPERF MSRs. In this case no need to use CPU cycles for > > frequency invariant accounting by reading APERF/MPERF MSRs. > > With this change frequency invariant account is only enabled in > > "passive" mode. > > > > Signed-off-by: Srinivas Pandruvada <[email protected] > > .com> > > --- > > [Note: The tick will be enabled later in the series when hwp > > dynamic > > boost is enabled] > > > > drivers/cpufreq/intel_pstate.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/drivers/cpufreq/intel_pstate.c > > b/drivers/cpufreq/intel_pstate.c > > index 17e566af..f686bbe 100644 > > --- a/drivers/cpufreq/intel_pstate.c > > +++ b/drivers/cpufreq/intel_pstate.c > > @@ -2040,6 +2040,8 @@ static int > > intel_pstate_register_driver(struct cpufreq_driver *driver) > > { > > int ret; > > > > + x86_arch_scale_freq_tick_disable(); > > + > > memset(&global, 0, sizeof(global)); > > global.max_perf_pct = 100; > > > > @@ -2052,6 +2054,9 @@ static int > > intel_pstate_register_driver(struct cpufreq_driver *driver) > > > > global.min_perf_pct = min_perf_pct_min(); > > > > + if (driver == &intel_cpufreq) > > + x86_arch_scale_freq_tick_enable(); > > This will unconditionally trigger the reading/calculation at each > tick > even though information is not actually consumed (e.g., running > performance or any other governor), right? Do we want that? Good point. I should call x86_arch_scale_freq_tick_disable() in performance mode switch for active mode.
Thanks, Srinivas > > Anyway, FWIW I started testing this on a E5-2609 v3 and I'm not > seeing > hackbench regressions so far (running with schedutil governor). > > Best, > > - Juri
