Re: performance of credit2 on hybrid workload

[George Dunlap <george.dunlap@citrix.com>]

On Mon, 2011-05-23 at 09:15 +0100, David Xu wrote:
> Hi,
> 
> 
> Xen4.1 datasheet tells that credit2 scheduler is designed for latency
> sensitive workloads. Does it have some improvement on the hybrid
> workload including both the cpu-bound and latency-sensitive i/o work?
> For example, if a VM runs a cpu-bound task burning the cpu and a
> i/o-bound (latency-sensitive) task simultaneously, will the latency be
> guaranteed? And how?

At the moment, the "mixed workload" problem, where a single VM does both
cpu-intensive and latency-sensitive* workloads, has not been addressed
yet.  I have some ideas, but I haven't implemented them yet.

* i/o-bound is not the same as latency sensitive.  They obviously go
together frequently, but I would make a distinction between them.  For
example, an scp (copy over ssh) can easily become cpu-bound if there is
competition for the cpu -- but it is nonetheless latency sensitive.  (I
guess to put it another way, a workload which is latency-sensitive may
become i/o-bound if its scheduling latency is too high.)

 -George