When the SCHED_DEADLINE scheduling class increases the CPU utilization, we should not wait for the rate limit, otherwise we may miss some deadline.
Tests using rt-app on Exynos5422 with up to 10 SCHED_DEADLINE tasks have shown reductions of even 10% of deadline misses with a negligible increase of energy consumption (measured through Baylibre Cape). Signed-off-by: Claudio Scordino <[email protected]> CC: Ingo Molnar <[email protected]> CC: Patrick Bellasi <[email protected]> CC: Dietmar Eggemann <[email protected]> CC: Morten Rasmussen <[email protected]> CC: Juri Lelli <[email protected]> CC: Viresh Kumar <[email protected]> CC: Vincent Guittot <[email protected]> CC: Todd Kjos <[email protected]> CC: Joel Fernandes <[email protected]> CC: [email protected] CC: [email protected] --- Changes from v2: - Rate limit ignored also in case of "fast switch" - Specific routine added --- Changes from v1: - Logic moved from sugov_should_update_freq() to sugov_update_single()/_shared() to not duplicate data structures - Rate limit not ignored in case of "fast switch" --- kernel/sched/cpufreq_schedutil.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 7936f54..13f9cce 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -260,6 +260,17 @@ static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) static inline bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) { return false; } #endif /* CONFIG_NO_HZ_COMMON */ +/* + * Make sugov_should_update_freq() ignore the rate limit when DL + * has increased the utilization. + */ +static inline +void set_dl_rate_limit(struct sugov_cpu *sg_cpu, struct sugov_policy *sg_policy) +{ + if (cpu_util_dl(cpu_rq(sg_cpu->cpu)) > sg_cpu->util_dl) + sg_policy->need_freq_update = true; +} + static void sugov_update_single(struct update_util_data *hook, u64 time, unsigned int flags) { @@ -273,6 +284,8 @@ static void sugov_update_single(struct update_util_data *hook, u64 time, sugov_set_iowait_boost(sg_cpu, time); sg_cpu->last_update = time; + set_dl_rate_limit(sg_cpu, sg_policy); + if (!sugov_should_update_freq(sg_policy, time)) return; @@ -354,6 +367,8 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time, raw_spin_lock(&sg_policy->update_lock); + set_dl_rate_limit(sg_cpu, sg_policy); + sugov_get_util(sg_cpu); sg_cpu->flags = flags; -- 2.7.4
