You cannot do that with the current code; to add such a parameter
would require major work to the scheduler.
On Wed, Jun 1, 2011 at 1:55 AM, David Xu <davidxu06@xxxxxxxxx> wrote:
> 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.
> 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.
>> 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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