Re: [Qemu-devel] [Patch]KVM: enabling per domain PLE

[Avi Kivity <avi@redhat.com>]

On 10/16/2012 08:53 AM, Hu, Xuekun wrote:
> Setting the same PLE parameter arbitrarily for different
> workloads is not a good solution. 

True.

> The solution enables
> per domain PLE which gives user ability to set PLE parameter
> for different domain for better performance.

The problem with this is that it requires an administrator to understand
the workload, not only of the guest, but also of other guests on the
machine.  With low overcommit, a high PLE window reduces unneeded exits,
but with high overcommit we need those exits to reduce spinning.

In addition, most kvm hosts don't have an administrator.  They are
controlled by a management system, which means we'll need some algorithm
in userspace to control the PLE window.  Taking the two together, we
need a dynamic (for changing workloads) algorithm.

There are threads discussing this dynamic algorithm, we are making slow
progress because it's such a difficult problem, but I think this is much
more useful than anything requiring user intervention.

-- 
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