On Mon, Sep 25, 2017 at 02:55:07PM +0100, Patrick Bellasi wrote: > On 23-Sep 07:04, Leo Yan wrote: > > Scheduler CFS class has variable 'capacity_margin' to calculate the > > capacity margin, and schedutil governor also needs to compensate the > > same margin for frequency tipping point. Below are formulas used in > > CFS class and schedutil governor separately: > > > > CFS: U` = U * capacity_margin / 1024 = U * 1.25 > > Schedutil: U` = U + U >> 2 = U + U * 0.25 = U * 1.25 > > > > This patch consolidates the capacity margin calculation so let > > schedutil to use same formula with CFS class. As result this can avoid > > the mismatch issue between schedutil and CFS class after change > > 'capacity_margin' to other values. > > > > Cc: Dietmar Eggemann <dietmar.eggem...@arm.com> > > Cc: Morten Rasmussen <morten.rasmus...@arm.com> > > Cc: Chris Redpath <chris.redp...@arm.com> > > Cc: Joel Fernandes <joe...@google.com> > > Cc: Vincent Guittot <vincent.guit...@linaro.org> > > Signed-off-by: Leo Yan <leo....@linaro.org> > > --- > > kernel/sched/cpufreq_schedutil.c | 5 +++-- > > kernel/sched/sched.h | 1 + > > 2 files changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/sched/cpufreq_schedutil.c > > b/kernel/sched/cpufreq_schedutil.c > > index 9209d83..067abbe 100644 > > --- a/kernel/sched/cpufreq_schedutil.c > > +++ b/kernel/sched/cpufreq_schedutil.c > > @@ -155,7 +155,8 @@ static void sugov_update_commit(struct sugov_policy > > *sg_policy, u64 time, > > * > > * next_freq = C * curr_freq * util_raw / max > > * > > - * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8. > > + * Take C = capacity_margin / 1024 = 1.25, so it's for the frequency > > tipping > > + * point at (util / max) = 0.8. > > * > > * The lowest driver-supported frequency which is equal or greater than > > the raw > > * next_freq (as calculated above) is returned, subject to policy min/max > > and > > @@ -168,7 +169,7 @@ static unsigned int get_next_freq(struct sugov_policy > > *sg_policy, > > unsigned int freq = arch_scale_freq_invariant() ? > > policy->cpuinfo.max_freq : policy->cur; > > > > - freq = (freq + (freq >> 2)) * util / max; > > + freq = (freq * capacity_margin / 1024) * util / max; > > The compiler should be smart enough but perhaps you can better use: > > freq *= (capacity_margin >> SCHED_CAPACITY_SHIFT)); > freq *= util / max;
Thanks for the suggestion. The '*=' has low precedence than other operators, will fix as below: freq = freq * capacity_margin >> SCHED_CAPACITY_SHIFT; freq = freq * util / max; > > if (freq == sg_policy->cached_raw_freq && sg_policy->next_freq != > > UINT_MAX) > > return sg_policy->next_freq; > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > > index 14db76c..cf75bdc 100644 > > --- a/kernel/sched/sched.h > > +++ b/kernel/sched/sched.h > > @@ -52,6 +52,7 @@ struct cpuidle_state; > > #define TASK_ON_RQ_MIGRATING 2 > > > > extern __read_mostly int scheduler_running; > > +extern unsigned int capacity_margin __read_mostly; > > > > extern unsigned long calc_load_update; > > extern atomic_long_t calc_load_tasks; > > -- > > 2.7.4 > > > > -- > #include <best/regards.h> > > Patrick Bellasi
