[Qemu-devel] Re: [RFC] Some more io-thread optimizations

[Marcelo Tosatti]

On Mon, Feb 14, 2011 at 10:50:42AM +0100, Jan Kiszka wrote:
> Hi,
> 
> patch below further reduces the io-thread overhead in tcg mode so that
> specifically emulating smp boxes gets noticeably faster. Its essence:
> poll the file descriptors until select returns 0, keeping the global
> mutex locked. This reduces ping pong with the vcpu threads, most
> noticeably in tcg mode where we run in lock-step.
> 
> Split up in two patches, I'm planning to route those changes via the kvm
> queue (as they collide with other patches there).
> 
> Jan

Not sure this makes sense for all cases. There could be scenarios where
a single pass is more efficient (think latency to acquire mutex from
vcpu context in kvm mode, with intensive file IO in progress).