RFR(S): 8196565: AIX: Clean up os::javaTimeNanos according to AIX/PASE specification

[David Holmes]

Hi Christoph,

On 1/02/2018 10:06 PM, Langer, Christoph wrote:
> Hi David,
> 
> thanks for looking. I'll change my code to use that constant.
> 
> One question, as I'm currently looking at the os timing functions: Do you know why in os_solaris.cpp, in os::getTimesSecs(), the process_real_time value is not taken from the result of times() but from getTimeNanos()? Otherwise getTimeSecs would be a good candidate to move to os_posix.cpp ...

I can only guess that as per the comment the intent was to ensure that 
"process_real_time" was consistent with other views of time ie 
os::elapsedTime and os::elapsedCounter.

The code was added by:

https://bugs.openjdk.java.net/browse/JDK-6468292

but there are no enlightening comments in that regard. And I don't know 
if times() would be using a different timebase than gethrtime().

David
-----

> Best regards
> Christoph
> 
> -----Original Message-----
> From: David Holmes [mailto:david.holmes at oracle.com]
> Sent: Donnerstag, 1. Februar 2018 12:10
> To: Langer, Christoph <christoph.langer at sap.com>; hotspot-runtime-dev at openjdk.java.net; ppc-aix-port-dev at openjdk.java.net
> Subject: Re: RFR(S): 8196565: AIX: Clean up os::javaTimeNanos according to AIX/PASE specification
> 
> Hi Christoph,
> 
> On 1/02/2018 7:11 PM, Langer, Christoph wrote:
>> Hi,
>>
>> please review a fix for the os::javaTimeNanos method on AIX.
>>
>> It implements the information we got from the AIX documentation and from the IBM folks regarding the behavior of mread_real_time on Pase.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8196565
>> Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8196565.0/
> 
> I took a look as I was curious :) I recognized the Solaris code for
> ensuring monotonic time. :) It all seems to do as you describe.
> 
> One nit - instead of (1000 * 1000 * 1000) you can use:
> 
> const jlong NANOSECS_PER_SEC      = CONST64(1000000000);
> 
> from ./hotspot/share/utilities/globalDefinitions.hpp
> 
> Cheers,
> David
> 
>> Thanks & Best regards
>> Christoph
>>