Re: [Qemu-devel] [PATCH v8 3/4] block: add block timer and throttling algorithm

[Marcelo Tosatti <mtosatti@redhat.com>]

On Mon, Sep 19, 2011 at 05:55:41PM +0800, Zhi Yong Wu wrote:
> On Wed, Sep 14, 2011 at 6:50 PM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
> > On Tue, Sep 13, 2011 at 11:09:46AM +0800, Zhi Yong Wu wrote:
> >> On Fri, Sep 9, 2011 at 10:44 PM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
> >> > On Thu, Sep 08, 2011 at 06:11:07PM +0800, Zhi Yong Wu wrote:
> >> >> Note:
> >> >>      1.) When bps/iops limits are specified to a small value such as 511 bytes/s, this VM will hang up. We are considering how to handle this senario.
> >> >
> >> > You can increase the length of the slice, if the request is larger than
> >> > slice_time * bps_limit.
> >> Yeah, but it is a challenge for how to increase it. Do you have some nice idea?
> >
> > If the queue is empty, and the request being processed does not fit the
> > queue, increase the slice so that the request fits.
> Sorry for late reply. actually, do you think that this scenario is
> meaningful for the user?
> Since we implement this, if the user limits the bps below 512
> bytes/second, the VM can also not run every task.
> Can you let us know why we need to make such effort?

It would be good to handle request larger than the slice.

It is not strictly necessary, but in case its not handled, a minimum
should be in place, to reflect maximum request size known. Being able to
specify something which crashes is not acceptable.