Re: [Qemu-block] [PATCH 00/13] throttle: Allow I/O bursts for a user-defined period of time

[Stefan Hajnoczi]

On Tue, Feb 16, 2016 at 04:38:04PM +0100, Alberto Garcia wrote:
> On Mon 15 Feb 2016 05:40:29 PM CET, Stefan Hajnoczi wrote:
> > On Fri, Feb 05, 2016 at 12:59:10PM +0200, Alberto Garcia wrote:
> >>  - With this series we set "a maximum of X operations/second for a
> >>    period of T seconds". If would also be possible to make it "a
> >>    maximum of X operations/second up to a total of Y operations". It
> >>    would be equivalent (Y = X * T) but I thought the current proposal
> >>    makes a more clear API.
> >
> > I find the diagram in the blog post clear.  The QEMU code is a little
> > harder to understand, it seems like there are too many variables and
> > special cases.  There are 4 core variables:
> >
> > 1. Refill rate (aka avg), e.g. 30 IOPS
> > 2. Max bucket level (aka max * burst_length), e.g. 5.4 million IOPS
> > 3. Burst rate (aka max), e.g. 3000 IOPS
> > 4. Current bucket level
> 
> The blog post uses the token bucket algorithm but QEMU uses the leaky
> bucket. They're equivalent, but one is the reverse of the other:

Yes, I find the token bucket approach clearer :).

Stefan

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