| Message ID | 20230802132925.686745535@infradead.org (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | cpuidle,teo: Improve TEO vs NOHZ | expand |
On Wed, Aug 02, 2023 at 03:24:34PM +0200, Peter Zijlstra wrote: > Remove some of the early exit cases that rely on state_count, since we > have the additional tick state. Declutters some of the next patches, can > possibly be re-instated later if desired. How does having that added tick state compensate for not checking the amount of states that the governor can choose from in the first place? [...] > - /* Check if there is any choice in the first place. */ > - if (drv->state_count < 2) { > - idx = 0; > - goto end; > - } > - if (!dev->states_usage[0].disable) { > - idx = 0; > - if (drv->states[1].target_residency_ns > duration_ns) > - goto end; > - } > - > - cpu_data->utilized = teo_cpu_is_utilized(dev->cpu, cpu_data); > - /* > - * If the CPU is being utilized over the threshold and there are only 2 > - * states to choose from, the metrics need not be considered, so choose > - * the shallowest non-polling state and exit. > - */ > - if (drv->state_count < 3 && cpu_data->utilized) { > - for (i = 0; i < drv->state_count; ++i) { > - if (!dev->states_usage[i].disable && > - !(drv->states[i].flags & CPUIDLE_FLAG_POLLING)) { > - idx = i; > - goto end; > - } > - } > - } What exactly is the benefit of removing this part? On systems with 2 idle states this will just make the governor pointlessly execute the metrics code when the result is already known regardless. Seems like pure added overhead. > - > /* > * Find the deepest idle state whose target residency does not exceed > * the current sleep length and the deepest idle state not deeper than > @@ -541,7 +512,7 @@ static int teo_select(struct cpuidle_dri > * If the CPU is being utilized over the threshold, choose a shallower > * non-polling state to improve latency > */ > - if (cpu_data->utilized) > + if (teo_cpu_is_utilized(dev->cpu, cpu_data)) > idx = teo_find_shallower_state(drv, dev, idx, duration_ns, true); > > end: > >
--- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -187,7 +187,6 @@ struct teo_bin { * @next_recent_idx: Index of the next @recent_idx entry to update. * @recent_idx: Indices of bins corresponding to recent "intercepts". * @util_threshold: Threshold above which the CPU is considered utilized - * @utilized: Whether the last sleep on the CPU happened while utilized */ struct teo_cpu { s64 time_span_ns; @@ -197,7 +196,6 @@ struct teo_cpu { int next_recent_idx; int recent_idx[NR_RECENT]; unsigned long util_threshold; - bool utilized; }; static DEFINE_PER_CPU(struct teo_cpu, teo_cpus); @@ -379,33 +377,6 @@ static int teo_select(struct cpuidle_dri duration_ns = tick_nohz_get_sleep_length(&delta_tick); cpu_data->sleep_length_ns = duration_ns; - /* Check if there is any choice in the first place. */ - if (drv->state_count < 2) { - idx = 0; - goto end; - } - if (!dev->states_usage[0].disable) { - idx = 0; - if (drv->states[1].target_residency_ns > duration_ns) - goto end; - } - - cpu_data->utilized = teo_cpu_is_utilized(dev->cpu, cpu_data); - /* - * If the CPU is being utilized over the threshold and there are only 2 - * states to choose from, the metrics need not be considered, so choose - * the shallowest non-polling state and exit. - */ - if (drv->state_count < 3 && cpu_data->utilized) { - for (i = 0; i < drv->state_count; ++i) { - if (!dev->states_usage[i].disable && - !(drv->states[i].flags & CPUIDLE_FLAG_POLLING)) { - idx = i; - goto end; - } - } - } - /* * Find the deepest idle state whose target residency does not exceed * the current sleep length and the deepest idle state not deeper than @@ -541,7 +512,7 @@ static int teo_select(struct cpuidle_dri * If the CPU is being utilized over the threshold, choose a shallower * non-polling state to improve latency */ - if (cpu_data->utilized) + if (teo_cpu_is_utilized(dev->cpu, cpu_data)) idx = teo_find_shallower_state(drv, dev, idx, duration_ns, true); end:
Remove some of the early exit cases that rely on state_count, since we have the additional tick state. Declutters some of the next patches, can possibly be re-instated later if desired. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- drivers/cpuidle/governors/teo.c | 31 +------------------------------ 1 file changed, 1 insertion(+), 30 deletions(-)