RFR (S): 7117303: VM uses non-monotonic time source and complains that it is non-monotonic

[Srinivas Ramakrishna]

Hi John -- Looks fine. Two minor comments:

(1) by defining an os::javaTimeNanosInMillis() you may be able to
consolidate the divide by NANOS_IN_MILLISEC to one place instead of it
appearing at each use.
(2) you might consolidate the commentary about monotonicity into
os::javaTimeNanosInMillis(), then at each client simly say "Protect against
possible nonmonotonicity"

That will reduce the number of repeated lines while still providing all of
the commentary in all the relevant places. (By the way, you might want to
check if there;s another CR with the same content which might be closed as
a dup of this... just a very vague recollection.)

reviewed.
-- ramki (opendjk: ysr)

On Fri, Dec 9, 2011 at 11:30 AM, John Cuthbertson <
john.cuthbertson at oracle.com> wrote:

> Hi Everyone,
>
> I have updated the comments based upon feedback from David Holmes. A new
> webrev can be found at: http://cr.openjdk.java.net/~**
> johnc/7117303/webrev.1/<http://cr.openjdk.java.net/%7Ejohnc/7117303/webrev.1/>
>
> Thanks,
>
> JohnC
>
>
> On 12/7/2011 9:59 AM, John Cuthbertson wrote:
>
>> Hi Everyone,
>>
>> Can I have a couple of volunteers review the changes for this CR? The
>> webrev can be found at: http://cr.openjdk.java.net/~**
>> johnc/7117303/webrev.0/<http://cr.openjdk.java.net/%7Ejohnc/7117303/webrev.0/>
>> .
>>
>> Summary:
>> I replaced the calls to os::javaTimeMillis() in the GC where we expect
>> monotonicity with calls os::javaTimeNanos(), converting the result to
>> milliseconds. os::javaTimeNanos(), at least on some configurations, does
>> guarantee monotonicity and so is a better alternative. The changes in the
>> os_<*> files are to make use of the named conversion constants I
>> added/moved to globalDefinitions.hpp - we seemed to have multiple names for
>> the same two constants.
>>
>> Testing: GC test suite on solaris and Linux, NSK tests on solaris, and
>> jprt.
>>
>> Thanks,
>>
>> JohnC
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/hotspot-gc-dev/attachments/20111211/ccb883bd/attachment.htm>