diff options
Diffstat (limited to 'drivers/cpufreq')
| -rw-r--r-- | drivers/cpufreq/cpufreq_governor.c | 58 | ||||
| -rw-r--r-- | drivers/cpufreq/cpufreq_governor.h | 6 |
2 files changed, 61 insertions, 3 deletions
diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c index e1c6433b16e0..9004450863be 100644 --- a/drivers/cpufreq/cpufreq_governor.c +++ b/drivers/cpufreq/cpufreq_governor.c @@ -36,14 +36,29 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu) struct od_dbs_tuners *od_tuners = dbs_data->tuners; struct cs_dbs_tuners *cs_tuners = dbs_data->tuners; struct cpufreq_policy *policy; + unsigned int sampling_rate; unsigned int max_load = 0; unsigned int ignore_nice; unsigned int j; - if (dbs_data->cdata->governor == GOV_ONDEMAND) + if (dbs_data->cdata->governor == GOV_ONDEMAND) { + struct od_cpu_dbs_info_s *od_dbs_info = + dbs_data->cdata->get_cpu_dbs_info_s(cpu); + + /* + * Sometimes, the ondemand governor uses an additional + * multiplier to give long delays. So apply this multiplier to + * the 'sampling_rate', so as to keep the wake-up-from-idle + * detection logic a bit conservative. + */ + sampling_rate = od_tuners->sampling_rate; + sampling_rate *= od_dbs_info->rate_mult; + ignore_nice = od_tuners->ignore_nice_load; - else + } else { + sampling_rate = cs_tuners->sampling_rate; ignore_nice = cs_tuners->ignore_nice_load; + } policy = cdbs->cur_policy; @@ -96,7 +111,36 @@ void dbs_check_cpu(struct dbs_data *dbs_data, int cpu) if (unlikely(!wall_time || wall_time < idle_time)) continue; - load = 100 * (wall_time - idle_time) / wall_time; + /* + * If the CPU had gone completely idle, and a task just woke up + * on this CPU now, it would be unfair to calculate 'load' the + * usual way for this elapsed time-window, because it will show + * near-zero load, irrespective of how CPU intensive that task + * actually is. This is undesirable for latency-sensitive bursty + * workloads. + * + * To avoid this, we reuse the 'load' from the previous + * time-window and give this task a chance to start with a + * reasonably high CPU frequency. (However, we shouldn't over-do + * this copy, lest we get stuck at a high load (high frequency) + * for too long, even when the current system load has actually + * dropped down. So we perform the copy only once, upon the + * first wake-up from idle.) + * + * Detecting this situation is easy: the governor's deferrable + * timer would not have fired during CPU-idle periods. Hence + * an unusually large 'wall_time' (as compared to the sampling + * rate) indicates this scenario. + */ + if (unlikely(wall_time > (2 * sampling_rate)) && + j_cdbs->copy_prev_load) { + load = j_cdbs->prev_load; + j_cdbs->copy_prev_load = false; + } else { + load = 100 * (wall_time - idle_time) / wall_time; + j_cdbs->prev_load = load; + j_cdbs->copy_prev_load = true; + } if (load > max_load) max_load = load; @@ -318,11 +362,19 @@ int cpufreq_governor_dbs(struct cpufreq_policy *policy, for_each_cpu(j, policy->cpus) { struct cpu_dbs_common_info *j_cdbs = dbs_data->cdata->get_cpu_cdbs(j); + unsigned int prev_load; j_cdbs->cpu = j; j_cdbs->cur_policy = policy; j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy); + + prev_load = (unsigned int) + (j_cdbs->prev_cpu_wall - j_cdbs->prev_cpu_idle); + j_cdbs->prev_load = 100 * prev_load / + (unsigned int) j_cdbs->prev_cpu_wall; + j_cdbs->copy_prev_load = true; + if (ignore_nice) j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h index bfb9ae14142c..c2a5b7e8070a 100644 --- a/drivers/cpufreq/cpufreq_governor.h +++ b/drivers/cpufreq/cpufreq_governor.h @@ -134,6 +134,12 @@ struct cpu_dbs_common_info { u64 prev_cpu_idle; u64 prev_cpu_wall; u64 prev_cpu_nice; + unsigned int prev_load; + /* + * Flag to ensure that we copy the previous load only once, upon the + * first wake-up from idle. + */ + bool copy_prev_load; struct cpufreq_policy *cur_policy; struct delayed_work work; /* |