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Re: [Xen-devel] [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks



On 07/11/2013 03:41 PM, Gleb Natapov wrote:
On Thu, Jul 11, 2013 at 03:40:38PM +0530, Raghavendra K T wrote:
Gleb,
Can you elaborate little more on what you have in mind regarding per
VM ple_window. (maintaining part of it as a per vm variable is clear
to
  me), but is it that we have to load that every time of guest entry?

Only when it changes, shouldn't be to often no?

Ok. Thinking how to do. read the register and writeback if there need
to be a change during guest entry?

Why not do it like in the patch you've linked? When value changes write it
to VMCS of the current vcpu.


Yes. can be done. So the running vcpu's ple_window gets updated only
after next pl-exit. right?
I am not sure what you mean. You cannot change vcpu's ple_window while
vcpu is in a guest mode.


I agree with that. Both of us are on the same page.
 What I meant is,
suppose the per VM ple_window changes when a vcpu x of that VM  was running,
it will get its ple_window updated during next run.


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