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;
> 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
