Re: dynamic-hz

Zwane Mwaikambo
2004-12-13T14:50:19Z

On Mon, 13 Dec 2004, Andrea Arcangeli wrote:

> You were the one making the case of the NMI, the NMI will screw
> completely any attempt of rearming the TSC accurately (though I don't
> mind too much, like for the sti; hlt, since NMI is pratically impossible
> to trigger in production, if a NMI is fired we've more troubles than the
> 1/HZ latency on a pending wakeup or on the system time taking the
> tangent ;)

I wouldn't say that NMI isn't used in production, if we didn't cater for
NMI it'd be hard to do high sample rate profiling with Oprofile and
dynamic-hz. I consider (non)kernel developers profiling code on systems as
production use.

> (btw, my firewall systemtime will get fixed too by dyanmic-hz HZ=100,
> it's pure waste to keep my firewall at HZ=1000 even if I didn't have
> constant irq-latency of 3/4msec [measured with rdtsc], though I didn't
> mention this yet because dynamic-hz in my firewall case would be a pure
> band-aid, even fixing the tick-lost adjustment would be a band-aid, the
> only thing to fix is the usb irq that runs for 3/4msec without returning).

I have a few personal systems which really would benefit too ;)

Thanks,
Zwane