Re: [Qemu-devel] change the default value of timeout

[Stefan Hajnoczi]

On Mon, Mar 12, 2012 at 3:17 AM, Zhang, Yang Z <address@hidden> wrote:
>        Currently, if not using nonblocking mode, the default timeout of 
> select() in main_loop_wait is 1000ms. There has no problem if you run few 
> VMs. But when running more VMs like 32 or 64, then the problem is coming. Our 
> experience shows that when running 64 idle VMs, the pkg C6 residency is 88% 
> by default and it goes to 90% when I change timeout to 10s. And 2% means 1 
> watt in my box. Since this is only a timeout value for select, so I suggest 
> to use a more reasonable way to set it rather than using a fixed value. For 
> example, using an argument to set it by user. But I am not sure whether 
> something else is depend on the timeout.

It's not obvious to me why we have a finite select(2) timeout in
main-loop.c:main_loop_wait().  State changes should use
qemu_notify_event() to leave the blocking select(2) call.

A user-visible argument doesn't seem like a solution to me.  How
should a user choose a value?

How about testing with an infinite timeout (timeout == NULL)?  Try
both KVM and TCG to see if it has weird effects.

Stefan