Bheve: Slow linux syscalls on AMD

[Willem Jan Withagen]

On 31-5-2014 2:13, Peter Grehan wrote:
> Hi Willem,
> 
>> So the question remains:
>>     Why is it taking so long on the AMD platform.
> 
>  The time difference looks a lot like a VM-exit roundtrip. My new AMD
> box is arriving shortly so I'll have a look into it.

Before running the getuid test:
vm exits due to interrupt window opening        0
vm exits due to nmi window opening              0
vm exits due to nested page fault               311094
vm exits for instruction emulation              159415683
number of vm exits for unknown reason           0
number of vm exits handled in userspace         0
number of vm exits due to exceptions            0
total number of vm exits                        353767137
vm exits due to external interrupt              177525597

Then calling getuid() 10^6 times

vm exits due to interrupt window opening        0
vm exits due to nmi window opening              0
vm exits due to nested page fault               311094
vm exits for instruction emulation              159589889
number of vm exits for unknown reason           0
number of vm exits handled in userspace         0
number of vm exits due to exceptions            0
total number of vm exits                        354157461
vm exits due to external interrupt              177730908

And that gives a difference of:
	390324

Which is not the regular amount of vm exits counted in the equal idle
time. So there seems to be some relation, but it is not 1:1...


--WjW