Re: [PATCH] stopmachine: add stopmachine_timeout

[Christian Borntraeger <borntraeger@de.ibm.com>]

Am Dienstag, 15. Juli 2008 schrieb Rusty Russell:
> > btw Rusty, I just had this "why didn't I think of that" moments. This is
> > actually another way of handling my workload. I mean it certainly does not
> > fix the root case of the problems and we still need other things that we
> > talked about (non-blocking module delete, lock-free module insertion, etc)
> > but at least in the mean time it avoids wedging the machines for good.
> > btw I'd like that timeout in milliseconds. I think 5 seconds is way tooooo
> > long :).
> 
> We can make it ms, sure.  200ms should be plenty of time: worst I ever saw 
was 
> 150ms, and that was some weird Power box doing crazy stuff.  I wouldn't be 
> surprised if you'd never see 1ms on your hardware.

I disagree that 5 seconds is to long :-). I even think having it default to 0 
is the safest option for virtualized environments. What if the host is paging 
like hell and the vcpu cannot run due to a missing page? In that case 200ms 
can be an incredible short amount of time. If the timeout triggers, 
stop_machine_run fails, but everything would work fine - it just takes 
longer.