PING: RFR: 8250598: Hyper-V is detected in spite of running on host OS

[David Holmes]

On 13/08/2020 11:12 am, Yasumasa Suenaga wrote:
> Hi Matthias, David,
> 
> I measured startup benchmarks with `Measure-Command 
> {.\jdk\build\windows-x86_64-server-release\images\jdk\bin\java.exe 
> --version}` on PowerShell.
> 
> * PC: Ryzen 3 3300X, 16GB memory
> * OS: Windows 10 x64 (May 2020 Update)
> * Java: jdk/jdk revision 60537
>      (Compiled by VS 2019 (16.7.0))
> 
> * without patch
> TotalMilliseconds : 70.2124
> TotalMilliseconds : 64.4465
> TotalMilliseconds : 59.0854
> TotalMilliseconds : 68.0255
> TotalMilliseconds : 72.6467
> average : 66.8833
> 
> * with webrev.01
> TotalMilliseconds : 81.7185
> TotalMilliseconds : 68.539
> TotalMilliseconds : 85.7226
> TotalMilliseconds : 72.6584
> TotalMilliseconds : 75.6091
> average : 76.84952
> 
> Overhead of WMI seems to be +10ms in this case.

Which is nearly 15%! Sorry but I just know Claes will be very unhappy if 
this were to go in as-is.

David
-----

> 
> Yasumasa
> 
> 
> On 2020/08/13 0:05, Baesken, Matthias wrote:
>>> I understand that if the process runs on Xen on other hypervisor 
>>> (e.g. KVM), information for Xen would be set between 0x40000100 and 
>>> 0x40010000.
>>> Ok, I will not remove the loop in new webrev, and will add comment 
>>> about it.
>>
>> Hi Yasumasa  , thanks !
>>
>> Regarding the WMI overhead , if you could  get some more info on this 
>> it would be better to judge if it is perfectly okay or  concerning .
>>
>> (I remember that I looked into it a couple of years ago , but decided 
>> not to use it in early VM startup ;  but have to confess this was just 
>> based on a "gut feeling",
>>   No micro benchmarks  )
>>
>> Best regards, Matthias
>>
>>