Messages in this thread Patch in this message | | | From | Pierre.Gondois@arm ... | Subject | [PATCH v2 1/2] sched/fair: Only compute base_energy_pd if necessary | Date | Thu, 29 Apr 2021 11:19:47 +0100 |
| |
From: Pierre Gondois <Pierre.Gondois@arm.com>
find_energy_efficient_cpu() searches the best energy CPU to place a task on. To do so, the energy of each performance domain (pd) is computed w/ and w/o the task placed in each pd.
The energy of a pd w/o the task (base_energy_pd) is computed prior knowing whether a CPU is available in the pd.
Move the base_energy_pd computation after looping through the CPUs of a pd and only computes it if at least one CPU is available.
Suggested-by: Xuewen Yan <xuewen.yan@unisoc.com> Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com> --- kernel/sched/fair.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0dba0ebc3657..c5351366fb93 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6620,13 +6620,10 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) for (; pd; pd = pd->next) { unsigned long cur_delta, spare_cap, max_spare_cap = 0; + bool compute_prev_delta = false; unsigned long base_energy_pd; int max_spare_cap_cpu = -1; - /* Compute the 'base' energy of the pd, without @p */ - base_energy_pd = compute_energy(p, -1, pd); - base_energy += base_energy_pd; - for_each_cpu_and(cpu, perf_domain_span(pd), sched_domain_span(sd)) { if (!cpumask_test_cpu(cpu, p->cpus_ptr)) continue; @@ -6647,25 +6644,34 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) if (!fits_capacity(util, cpu_cap)) continue; - /* Always use prev_cpu as a candidate. */ if (cpu == prev_cpu) { - prev_delta = compute_energy(p, prev_cpu, pd); - prev_delta -= base_energy_pd; - best_delta = min(best_delta, prev_delta); - } - - /* - * Find the CPU with the maximum spare capacity in - * the performance domain - */ - if (spare_cap > max_spare_cap) { + /* Always use prev_cpu as a candidate. */ + compute_prev_delta = true; + } else if (spare_cap > max_spare_cap) { + /* + * Find the CPU with the maximum spare capacity + * in the performance domain. + */ max_spare_cap = spare_cap; max_spare_cap_cpu = cpu; } } + if (max_spare_cap_cpu < 0 && !compute_prev_delta) + continue; + + /* Compute the 'base' energy of the pd, without @p */ + base_energy_pd = compute_energy(p, -1, pd); + base_energy += base_energy_pd; + + if (compute_prev_delta) { + prev_delta = compute_energy(p, prev_cpu, pd); + prev_delta -= base_energy_pd; + best_delta = min(best_delta, prev_delta); + } + /* Evaluate the energy impact of using this CPU. */ - if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) { + if (max_spare_cap_cpu >= 0) { cur_delta = compute_energy(p, max_spare_cap_cpu, pd); cur_delta -= base_energy_pd; if (cur_delta < best_delta) { -- 2.17.1
| |