Re: [Adeos-main] 260 uSec latency and no idea why

[Dirk Roloff <roloff@domain.hid>]

Am Donnerstag, 11. März 2004 20:04 schrieb Paolo Mantegazza:

Hi Paolo,

> Dirk Roloff wrote:
> Have you tried using rt_get_cpu_time_ns to avoid mixing up with Linux
> stuff? 


No i don't because i am not using rtai. I "just" use an adeos patched kernel.
But i changed the do_gettimeofday() by a rdtsc call. I dont want to know the time,
just the time elapsed. So i dont need the time calculation done by do_gettimeofday()
and i avoid mixing stuff. But the results are the same. :-(

>Have you checkd the interrupt level acknolwdge jitter/latency using
> the calibration tool available in RTAI?

again - no rtai

> Can you change your code so that it can be used anywhere? In such a case
> it would be simple to run it on a safe machine (e.g. mine) and see if it
> can be repeated, or is machine specific (yours).

Yes but it will not help a lot. I can't see such a latency on other machines.
f.e. on my Box here at home 7-17 MicroSec in the adeos domain.
And i try stressing the Box- but its a complete different h/ware.

So it must be the celeron box or some kernel/compiler settings on it.

But what is able to delay the delivery of an interrupt if there is no one 
calling cli or masking irq's (Both is prohibited by adeos isn't it ?)

One thing would be waking a suspended cpu - but i disabled APM.
Someone told me Intel SpeedStep switching the mode will take hundrets of MicroSecs
but i didn't find what this is yet. Have to google some more.

Dirk.