Hi,
On 30/11/17 11:47, Patrick Bellasi wrote:
> The policy in use for RT/DL tasks sets the maximum frequency when a task
> in these classes calls for a cpufreq_update_util(). However, the
> current implementation is still enforcing a frequency switch rate
> limiting when these tasks are running.
> This is potentially working against the goal to switch to the maximum OPP
> when RT tasks are running. In certain unfortunate cases it can also happen
> that a RT task almost completes its activation at a lower OPP.
>
> This patch overrides on purpose the rate limiting configuration
> to better serve RT/DL tasks. As long as a frequency scaling operation
> is not in progress, a frequency switch is always authorized when
> running in "rt_mode", i.e. the current task in a CPU belongs to the
> RT/DL class.
>
> Signed-off-by: Patrick Bellasi <[email protected]>
> Reviewed-by: Dietmar Eggemann <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Rafael J. Wysocki <[email protected]>
> Cc: Viresh Kumar <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
>
> ---
> Changes from v2:
> - rebased on v4.15-rc1
>
> Change-Id: I733d47b9e265cebb2e3e5e71a3cd468e9be002d1
Luckily this gets ignored... :)
> ---
> kernel/sched/cpufreq_schedutil.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/sched/cpufreq_schedutil.c
> b/kernel/sched/cpufreq_schedutil.c
> index 40521d59630b..3eea8884e61b 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -74,7 +74,8 @@ static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
>
> /************************ Governor internals ***********************/
>
> -static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64
> time)
> +static bool sugov_should_update_freq(struct sugov_policy *sg_policy,
> + u64 time, bool rt_mode)
> {
> s64 delta_ns;
>
> @@ -111,6 +112,10 @@ static bool sugov_should_update_freq(struct sugov_policy
> *sg_policy, u64 time)
> return true;
> }
>
> + /* Always update if a RT/DL task is running */
> + if (rt_mode)
> + return true;
> +
> delta_ns = time - sg_policy->last_freq_update_time;
> return delta_ns >= sg_policy->freq_update_delay_ns;
> }
> @@ -268,11 +273,6 @@ static void sugov_update_single(struct update_util_data
> *hook, u64 time,
> sugov_set_iowait_boost(sg_cpu, time, flags);
> sg_cpu->last_update = time;
>
> - if (!sugov_should_update_freq(sg_policy, time))
> - return;
> -
> - busy = sugov_cpu_is_busy(sg_cpu);
> -
> /*
> * While RT/DL tasks are running we do not want FAIR tasks to
> * overvrite this CPU's flags, still we can update utilization and
> @@ -281,6 +281,11 @@ static void sugov_update_single(struct update_util_data
> *hook, u64 time,
> rt_mode = task_has_dl_policy(current) ||
> task_has_rt_policy(current) ||
> (flags & SCHED_CPUFREQ_RT_DL);
> + if (!sugov_should_update_freq(sg_policy, time, rt_mode))
> + return;
> +
> + busy = sugov_cpu_is_busy(sg_cpu);
> +
> if (rt_mode) {
> next_f = policy->cpuinfo.max_freq;
> } else {
> @@ -379,7 +384,7 @@ static void sugov_update_shared(struct update_util_data
> *hook, u64 time,
> sugov_set_iowait_boost(sg_cpu, time, flags);
> sg_cpu->last_update = time;
>
> - if (sugov_should_update_freq(sg_policy, time)) {
> + if (sugov_should_update_freq(sg_policy, time, rt_mode)) {
> next_f = rt_mode
> ? sg_policy->policy->cpuinfo.max_freq
> : sugov_next_freq_shared(sg_cpu, time);
Reviewed-by: Juri Lelli <[email protected]>
I wonder if we would also need some way to trigger a back to back update
as soon as a currently running one finishes and an RT/DL task asked for
an update (without waiting for the next tick).
Best,
Juri
