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Wysocki" , Pavel Machek , Len Brown , Greg Kroah-Hartman , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider Cc: Saravana Kannan , Geert Uytterhoeven , Marek Vasut , Bird@google.com, Tim , kernel-team@android.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org As of today, the scheduler doesn't spread out all the kworker threads across all the available CPUs during suspend/resume. This causes significant resume latency during the dpm_resume*() phases. System resume latency is a very user-visible event. Reducing the latency is more important than trying to be energy aware during that period. Since there are no userspace processes running during this time and this is a very short time window, we can simply disable EAS during resume so that the parallel resume of the devices is spread across all the CPUs. On a Pixel 6, averaging over 100 suspend/resume cycles, the new logic plus disabling EAS for resume yields significant improvements: +---------------------------+-----------+------------+------------------+ | Phase | Old full sync | New full async | % change | | | | + EAS disabled | | +---------------------------+-----------+------------+------------------+ | Total dpm_suspend*() time | 107 ms | 62 ms | -42% | +---------------------------+-----------+------------+------------------+ | Total dpm_resume*() time | 75 ms | 61 ms | -19% | +---------------------------+-----------+------------+------------------+ | Sum | 182 ms | 123 ms | -32% | +---------------------------+-----------+------------+------------------+ Signed-off-by: Saravana Kannan --- kernel/power/suspend.c | 16 ++++++++++++++++ kernel/sched/topology.c | 13 +++++++++++++ 2 files changed, 29 insertions(+) diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c index 09f8397bae15..7304dc39958f 100644 --- a/kernel/power/suspend.c +++ b/kernel/power/suspend.c @@ -393,6 +393,12 @@ void __weak arch_suspend_enable_irqs(void) local_irq_enable(); } +/* + * Intentionally not part of a header file to avoid risk of abuse by other + * drivers. + */ +void sched_set_energy_aware(unsigned int enable); + /** * suspend_enter - Make the system enter the given sleep state. * @state: System sleep state to enter. @@ -468,6 +474,15 @@ static int suspend_enter(suspend_state_t state, bool *wakeup) Platform_wake: platform_resume_noirq(state); + /* + * We do this only for resume instead of suspend and resume for these + * reasons: + * - Performance is more important than power for resume. + * - Power spent entering suspend is more important for suspend. Also, + * stangely, disabling EAS was making suspent a few milliseconds + * slower in my testing. + */ + sched_set_energy_aware(0); dpm_resume_noirq(PMSG_RESUME); Platform_early_resume: @@ -520,6 +535,7 @@ int suspend_devices_and_enter(suspend_state_t state) Resume_devices: suspend_test_start(); dpm_resume_end(PMSG_RESUME); + sched_set_energy_aware(1); suspend_test_finish("resume devices"); trace_suspend_resume(TPS("resume_console"), state, true); resume_console(); diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 9748a4c8d668..c069c0b17cbf 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -284,6 +284,19 @@ void rebuild_sched_domains_energy(void) mutex_unlock(&sched_energy_mutex); } +void sched_set_energy_aware(unsigned int enable) +{ + int state; + + if (!sched_is_eas_possible(cpu_active_mask)) + return; + + sysctl_sched_energy_aware = enable; + state = static_branch_unlikely(&sched_energy_present); + if (state != sysctl_sched_energy_aware) + rebuild_sched_domains_energy(); +} + #ifdef CONFIG_PROC_SYSCTL static int sched_energy_aware_handler(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos)