On 2012-03-18 11:17 AM, Johannes Berg wrote:
> On Sun, 2012-03-18 at 00:00 +0100, Felix Fietkau wrote:
>> Calling mod_timer from the rx/tx hotpath is somewhat expensive, and the
>> timeout doesn't need to be so precise.
>>
>> Switch to a different strategy: Schedule the timer initially, store jiffies
>> of all last rx/tx activity which would previously modify the timer, and
>> let the timer re-arm itself after checking the last rx/tx timestamp.
>
> I don't like this. It's not the optimisation you think it is on other
> ("embedded") systems where firing a timer is more expensive.
>
> You're trading power consumption against CPU utilisation by causing the
> timer to wake up.
I considered that was well, but didn't think one wakeup every 5 seconds
or so would be significant. Would you take the patch if I change the
timer to be deferrable, so that it doesn't cause wakeups by itself?
- Felix
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