Re: Re: performance of credit2 on hybrid workload

[David Xu <davidxu06@gmail.com>]

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Hi George,

Could you share some ideas about how to addressed the  "mixed workload"
problem,  where a single VM does both
cpu-intensive and latency-sensitive workloads, even though you haven't
implemented it yet?  I am also working on it, maybe I can try some methods
and give you feedback. Thanks.

Regards,
Cong



2011/6/1 George Dunlap <George.Dunlap@eu.citrix.com>

> You cannot do that with the current code; to add such a parameter
> would require major work to the scheduler.
>
>  -George
>
> On Wed, Jun 1, 2011 at 1:55 AM, David Xu <davidxu06@gmail.com> wrote:
> > Hi,
> > I want to reduce the latency of a specific VM. How should I do based on
> > credit scheduler? For example, I will add another parameter latency
> besides
> > weight and cap, and schedule the vcpu whose VM holds the least latency
> > firstly each time. Thanks.
> > Regards,
> > Cong
> >
> > 2011/5/26 George Dunlap <george.dunlap@citrix.com>
> >>
> >> Please reply to the list. :-)
> >>
> >> Also, this is a question about credit1, so it should arguably be a
> >> different thread.
> >>
> >>  -George
> >>
> >> On Wed, 2011-05-25 at 19:34 +0100, David Xu wrote:
> >> > Thanks. The boost mechanism in credit can significantly reduce the
> >> > scheduling latency for pure I/O workload. Since the minimum interval
> >> > of credit scheduling is 10ms, the magnitude of latency for the target
> >> > VM should be 10ms (except the credit is not used up and vcpu remain
> >> > the head of runqueue ) as well. Why the real latency in my test (Ping
> >> > the target VM) is much shorter than 10ms? Does the vcpu of target VM
> >> > remain the head of runqueue if it was boosted?
> >> >
> >> >
> >> > David
> >> >
> >> > 2011/5/25 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
> >> >
> >> >
> >> >
> >>
> >>
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@lists.xensource.com
> > http://lists.xensource.com/xen-devel
> >
> >
>

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