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Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migrat
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration |
Date: |
Fri, 10 May 2013 15:17:59 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, May 10, 2013 at 08:07:51AM -0500, Anthony Liguori wrote:
> Chegu Vinod <address@hidden> writes:
>
> > If a user chooses to turn on the auto-converge migration capability
> > these changes detect the lack of convergence and throttle down the
> > guest. i.e. force the VCPUs out of the guest for some duration
> > and let the migration thread catchup and help converge.
> >
> > Verified the convergence using the following :
> > - SpecJbb2005 workload running on a 20VCPU/256G guest(~80% busy)
> > - OLTP like workload running on a 80VCPU/512G guest (~80% busy)
> >
> > Sample results with SpecJbb2005 workload : (migrate speed set to 20Gb and
> > migrate downtime set to 4seconds).
>
> Would it make sense to separate out the "slow the VCPU down" part of
> this?
>
> That would give a management tool more flexibility to create policies
> around slowing the VCPU down to encourage migration.
>
> In fact, I wonder if we need anything in the migration path if we just
> expose the "slow the VCPU down" bit as a feature.
>
> Slow the VCPU down is not quite the same as setting priority of the VCPU
> thread largely because of the QBL so I recognize the need to have
> something for this in QEMU.
Rather than the priority, could you perhaps do the VCPU slow down
using cfs_quota_us + cfs_period_us settings though ? These let you
place hard caps on schedular time afforded to vCPUs and we can already
control those via libvirt + cgroups.
Daniel
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- Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration, (continued)
- Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration, Paolo Bonzini, 2013/05/10
- Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration,
Daniel P. Berrange <=
- Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration, Anthony Liguori, 2013/05/10
- Re: [Qemu-devel] [RFC PATCH v5 3/3] Force auto-convegence of live migration, Daniel P. Berrange, 2013/05/13
[Qemu-devel] [RFC PATCH v5 1/3] Introduce async_run_on_cpu(), Chegu Vinod, 2013/05/09