Hi Joel, On Sun, Oct 01, 2017 at 06:02:24PM -0700, Joel Fernandes wrote: > Hi Leo, > > On Sun, Oct 1, 2017 at 5:30 PM, Leo Yan <leo....@linaro.org> wrote: > > Scheduler CFS class has variable 'capacity_margin' to calculate the > > s/calculate/represent/ ? > > > 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 > > You should mention in the commit message, at the moment > capacity_margin is 1280 which makes 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 > > As a result. > > > the mismatch issue between schedutil and CFS class after change > > 'capacity_margin' to other values. > > This didn't make sense to me. May be you meant: > > This patch consolidates the usage of the capacity margin value and > lets schedutil use the same formula as the CFS class. Thus we can > avoid the mismatch between schedutil and CFS class if > 'capacity_margin' is changed to other values in the future.
Yeah, thanks for the suggestion. And accept all upper comment. Will refine for new patch. Thanks, Leo Yan > > 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> > > Cc: Patrick Bellasi <patrick.bell...@arm.com> > > Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com> > > Signed-off-by: Leo Yan <leo....@linaro.org> > > --- > > kernel/sched/cpufreq_schedutil.c | 6 ++++-- > > kernel/sched/sched.h | 1 + > > 2 files changed, 5 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/sched/cpufreq_schedutil.c > > b/kernel/sched/cpufreq_schedutil.c > > index 9209d83..13cc243 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 above comment assumes capacity_margin is 1280. If for any reason > the capacity_margin is changed to something else, then the comment > wont make sense anymore. > > thanks, > > - Joel
