device polling and weird timer interrupt count from vmstat
Artem Kuchin
matrix at itlegion.ru
Mon Sep 24 10:58:26 PDT 2007
Anyone any clue on this issue:
Artem Kuchin wrote:
> I enabled device polling in the kernel, in nics and
> set HZ=1000.
>
> How, when i do
>
> omni2# vmstat -i
>
> i see
>
> interrupt total rate
> irq14: ata0 47 0
> irq15: ata1 41 0
> irq28: em0 2268 4
> irq72: twe0 58380 120
> cpu0: timer 965994 1995
> cpu3: timer 1 0
> cpu1: timer 1 0
> cpu2: timer 965857 1995
> Total 1992589 4116
>
>
> (it is dual xeon with HT, HT disabled, that why cpu3 and cpu1 are
> zero).
>
> What i don't understand is why timer rate on each cpu is 1995? I have
> set it to 1000, not 1995 or 2000. I have seen it showing 2000 on
> another box.
> So
> 1) why not 1000?
> 2) if it is supposed to be doubled (why?) when why not 2000?
> 3) Is timer int really generated on each cpu? Am i really wasting cpu
> time on ~4000 ints per second?
> 4) does twe driver use polling? whay about twa? how to check it in
> the sources?
More information about the freebsd-stable
mailing list