RFR: 8253030: ZGC: Change ZMarkCompleteTimeout unit to microseconds

[Per Lidén]

On Fri, 11 Sep 2020 01:16:34 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> The ZMarkCompleteTimeout is currently specified in milliseconds, and its value is 1 (i.e. as low as it can be). In
>> preparation for using a lower time out value than 1ms we should change the ZMarkCompleteTimeout unit to be
>> microseconds, instead of milliseconds.
>
> Change looks good.  But I wonder, why choose microseconds as the units?  That seems to be almost never used in HotSpot.

@kimbarrett Thanks for reviewing. I used micros because it seems like the natural unit to use here. Using nanos seems a
bit overkill, as we will never need that precision and it would just add a bunch of zeros to the constant, which I'm
not sure would help readability. What unit did you have in mind?

-------------

PR: https://git.openjdk.java.net/jdk/pull/120