From: Suren Baghdasaryan <surenb@google.com> To: Patrick Bellasi <patrick.bellasi@arm.com> Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Viresh Kumar <viresh.kumar@linaro.org>, Vincent Guittot <vincent.guittot@linaro.org>, Paul Turner <pjt@google.com>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Morten Rasmussen <morten.rasmussen@arm.com>, Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>, Joel Fernandes <joelaf@google.com>, Steve Muckle <smuckle@google.com> Subject: Re: [PATCH v2 12/12] sched/core: uclamp: use percentage clamp values Date: Tue, 24 Jul 2018 10:11:54 -0700 [thread overview] Message-ID: <CAJuCfpHddNKXNVBs21sCADcHjW7zxxue8jg1B4KbPh-QLNe46g@mail.gmail.com> (raw) In-Reply-To: <20180724164303.GB3162@e110439-lin> On Tue, Jul 24, 2018 at 9:43 AM, Patrick Bellasi <patrick.bellasi@arm.com> wrote: > On 21-Jul 21:04, Suren Baghdasaryan wrote: >> On Mon, Jul 16, 2018 at 1:29 AM, Patrick Bellasi >> <patrick.bellasi@arm.com> wrote: > > [...] > >> > +static inline unsigned int scale_from_percent(unsigned int pct) >> > +{ >> > + WARN_ON(pct > 100); >> > + >> > + return ((SCHED_FIXEDPOINT_SCALE * pct) / 100); >> > +} >> > + >> > +static inline unsigned int scale_to_percent(unsigned int value) >> > +{ >> > + unsigned int rounding = 0; >> > + >> > + WARN_ON(value > SCHED_FIXEDPOINT_SCALE); >> > + >> > + /* Compensate rounding errors for: 0, 256, 512, 768, 1024 */ >> > + if (likely((value & 0xFF) && ~(value & 0x700))) >> > + rounding = 1; >> >> Hmm. I don't think ~(value & 0x700) will ever yield FALSE... What am I missing? > > So, 0x700 is the topmost 3 bits sets (111 0000 0000) which different > configuration corresponds to: > > 001 0000 0000 => 256 > 010 0000 0000 => 512 > 011 0000 0000 => 768 > 100 0000 0000 => 1024 > > Thus, if 0x700 matches then we have one of these values in input and > for these cases we have to add a unit to the percentage value. > > For the case (value == 0) we translate it into 0% thanks to the check > on (value & 0xFF) to ensure rounding = 0. > I think just (value & 0xFF) is enough to get you the right behavior. ~(value & 0x700) is not needed, it's effectively a NoOp which always yields TRUE. For any *value* (value & 0x700) == 0x...00 and ~(value & 0x700) == 0x...FF == TRUE. > Here is a small python snippet I've used to check the conversion of > all the possible percentage values: > > ---8<--- > values = range(0, 101) > for pct in xrange(0, 101): > util = int((1024 * pct) / 100) > rounding = 1 > if not ((util & 0xFF) and ~(util & 0x700)): > print "Fixing util_to_perc({:3d} => {:4d})".format(pct, util) > rounding = 0 > pct2 = (rounding + ((100 * util) / 1024)) > if pct2 in values: > values.remove(pct2) > if pct != pct2: > print "Convertion failed for: {:3d} => {:4d} => {:3d}".format(pct, util, pct2) > if values: > print "ERROR: not all percentage values converted" > ---8<--- > > -- > #include <best/regards.h> > > Patrick Bellasi
next prev parent reply other threads:[~2018-07-24 17:11 UTC|newest] Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-07-16 8:28 [PATCH v2 00/12] Add utilization clamping support Patrick Bellasi 2018-07-16 8:28 ` [PATCH v2 01/12] sched/core: uclamp: extend sched_setattr to support utilization clamping Patrick Bellasi 2018-07-17 17:50 ` Joel Fernandes 2018-07-18 8:42 ` Patrick Bellasi 2018-07-18 17:02 ` Joel Fernandes 2018-07-17 18:04 ` Joel Fernandes 2018-07-16 8:28 ` [PATCH v2 02/12] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Patrick Bellasi 2018-07-19 23:51 ` Suren Baghdasaryan 2018-07-20 15:11 ` Patrick Bellasi 2018-07-21 0:25 ` Suren Baghdasaryan 2018-07-23 13:36 ` Patrick Bellasi 2018-07-16 8:28 ` [PATCH v2 03/12] sched/core: uclamp: add CPU's clamp groups accounting Patrick Bellasi 2018-07-20 20:25 ` Suren Baghdasaryan 2018-07-16 8:28 ` [PATCH v2 04/12] sched/core: uclamp: update CPU's refcount on clamp changes Patrick Bellasi 2018-07-16 8:28 ` [PATCH v2 05/12] sched/cpufreq: uclamp: add utilization clamping for FAIR tasks Patrick Bellasi 2018-07-16 8:29 ` [PATCH v2 06/12] sched/cpufreq: uclamp: add utilization clamping for RT tasks Patrick Bellasi 2018-07-16 8:29 ` [PATCH v2 07/12] sched/core: uclamp: enforce last task UCLAMP_MAX Patrick Bellasi 2018-07-21 1:23 ` Suren Baghdasaryan 2018-07-23 15:02 ` Patrick Bellasi 2018-07-23 16:40 ` Suren Baghdasaryan 2018-07-16 8:29 ` [PATCH v2 08/12] sched/core: uclamp: extend cpu's cgroup controller Patrick Bellasi 2018-07-21 2:37 ` Suren Baghdasaryan 2018-07-21 3:16 ` Suren Baghdasaryan 2018-07-23 15:17 ` Patrick Bellasi 2018-07-23 15:30 ` Tejun Heo 2018-07-23 17:22 ` Patrick Bellasi 2018-07-24 13:29 ` Tejun Heo 2018-07-24 15:39 ` Patrick Bellasi 2018-07-27 0:39 ` Joel Fernandes 2018-07-27 8:09 ` Quentin Perret 2018-07-16 8:29 ` [PATCH v2 09/12] sched/core: uclamp: map TG's clamp values into CPU's clamp groups Patrick Bellasi 2018-07-16 8:29 ` [PATCH v2 10/12] sched/core: uclamp: use TG's clamps to restrict Task's clamps Patrick Bellasi 2018-07-22 3:05 ` Suren Baghdasaryan 2018-07-23 15:40 ` Patrick Bellasi 2018-07-23 17:11 ` Suren Baghdasaryan 2018-07-24 9:56 ` Patrick Bellasi 2018-07-24 15:28 ` Suren Baghdasaryan 2018-07-24 15:49 ` Patrick Bellasi 2018-07-16 8:29 ` [PATCH v2 11/12] sched/core: uclamp: update CPU's refcount on TG's clamp changes Patrick Bellasi 2018-07-22 3:17 ` Suren Baghdasaryan 2018-07-16 8:29 ` [PATCH v2 12/12] sched/core: uclamp: use percentage clamp values Patrick Bellasi 2018-07-22 4:04 ` Suren Baghdasaryan 2018-07-24 16:43 ` Patrick Bellasi 2018-07-24 17:11 ` Suren Baghdasaryan [this message] 2018-07-24 17:17 ` Patrick Bellasi 2018-07-17 13:03 ` [PATCH v2 00/12] Add utilization clamping support Joel Fernandes 2018-07-17 13:41 ` Patrick Bellasi
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