ath / 802.11n performance issues and timer code

[Adrian Chadd]

On 26 September 2011 22:53, John Baldwin <jhb at freebsd.org> wrote:

> I meant do the timer settings affect UDP performance?  I.e. does idletick=1
> change UDP performance at all?

I'll check that and get back to you.

But please keep in mind that the first time I tried this and saw
immediate results was with the device in hostap mode - where ethernet
and wlan0 are bridged via if_bridge.
There's no TCP or UDP state being handled at all.

>> Which should wake up a/the taskqueue thread in question and have it
>> immediately run the next task on the queue. The taskqueue doesn't have
>> any form of timer/callout; it's just a "submit this to get run." When
>> will it be run? I hope not at the next tick, not if the CPU is free.
>
> No, that scheduling is synchronous.  Anytime a thread is scheduled the
> scheduler will check if it should preempt the current thread to run the
> new thread.

I admit I don't quite understand yet the scheduler and event/timer
handling code. What about if nothing is currently scheduled and the
CPU is idle? When will the idle process get tickled? I assume it would
preempt the idle process immediately and run the taskqueue kernel
thread, right? Would there ever be a situation where it doesn't do
this?



Adrian