Messages in this thread | | | Date | Thu, 3 Aug 2023 11:12:30 +0100 | From | Kajetan Puchalski <> | Subject | Re: [RFC][PATCH v2 3/5] cpuidle/teo: Simplify a little |
| |
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: > >
| |