Messages in this thread | | | Date | Thu, 11 Jul 2013 16:44:15 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks |
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On 07/11/2013 04:26 PM, Gleb Natapov wrote: > On Thu, Jul 11, 2013 at 04:23:58PM +0530, Raghavendra K T wrote: >> 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. > Ah, I think "per VM" is what confuses me. Why do you want to have "per > VM" ple_windows and not "per vcpu" one? With per vcpu one ple_windows > cannot change while vcpu is running. >
Okay. Got that. My initial feeling was vcpu does not "feel" the global load. But I think that should be of no problem. instead we will not need atomic operations to update ple_window, which is better.
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