Re: [Xen-devel] Re: performance of credit2 on hybrid workload

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

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@xxxxxxxxx> 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@xxxxxxxxxx>
>>
>> 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@xxxxxxxxxx>
>> >
>> >         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
>> >
>> >
>> >
>>
>>
>
>
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