Messages in this thread | | | Date | Thu, 11 Jul 2013 14:43:03 +0530 | From | Raghavendra K T <> | Subject | Re: [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks |
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On 07/10/2013 04:03 PM, Gleb Natapov wrote: [...] trimmed
>>> Yes. you are right. dynamic ple window was an attempt to solve it. >>> >>> Probelm is, reducing the SPIN_THRESHOLD is resulting in excess halt >>> exits in under-commits and increasing ple_window may be sometimes >>> counter productive as it affects other busy-wait constructs such as >>> flush_tlb AFAIK. >>> So if we could have had a dynamically changing SPIN_THRESHOLD too, that >>> would be nice. >>> >> >> Gleb, Andrew, >> I tested with the global ple window change (similar to what I posted >> here https://lkml.org/lkml/2012/11/11/14 ), > This does not look global. It changes PLE per vcpu.
Okay. Got it. I was thinking it would change the global value. But IIRC It is changing global sysfs value and per vcpu ple_window. Sorry. I missed this part yesterday.
> >> But did not see good result. May be it is good to go with per VM >> ple_window. >> >> 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?
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