On 07/11/2013 03:18 PM, Gleb Natapov wrote:
On Thu, Jul 11, 2013 at 02:43:03PM +0530, Raghavendra K T wrote:
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.
Yes, it changes sysfs value but this does not affect already created
vcpus.
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?
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?
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