On 09/26/2013 08:24 AM, Viresh Kumar wrote:
On 26 September 2013 04:08, Daniel Lezcano daniel.lezcano@linaro.org wrote:
On 09/22/2013 03:21 AM, Viresh Kumar wrote:
If entered_state == 0, we don't need to set dev->last_residency to 'diff' as we will be setting it to zero without using its new value.
I don't get it, can you elaborate.
Sure.. We have following code in cpuidle_enter_state():
diff = ktime_to_us(ktime_sub(time_end, time_start)); if (diff > INT_MAX) diff = INT_MAX; dev->last_residency = (int) diff; if (entered_state >= 0) { /* Update cpuidle counters */ /* This can be moved to within driver enter routine * but that results in multiple copies of same code. */ dev->states_usage[entered_state].time += dev->last_residency; dev->states_usage[entered_state].usage++; } else { dev->last_residency = 0; }
We are setting last_residency to 0 when (entered_state < 0) and aren't using the value of "diff". So, we can actually skip calculations of time_end, diff and last_residency when (entered_state < 0).. Makes sense?
Yes I agree, but why are you saying "If entered_state == 0, we don't need to ..." ?
We can be a long time in this state (eg. if the prediction is false).
Okay.. I didn't get it :)