RFR: 8277807: Increase default initial concurrent refinement threshold [v2]

[Thomas Schatzl]

On Thu, 25 Nov 2021 04:32:32 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Please review this change to the default initial concurrent refinement
>> threshold.  The new value takes into account options that should provide a
>> starting point that is closer to the long-term range.
>> 
>> Testing:
>> mach5 tier1
>> manually verified logged initial value matched expectations.
>
> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update copyright

Lgtm.

src/hotspot/share/gc/g1/g1ConcurrentRefine.cpp line 258:

> 256:     // rate_1 is a relatively conservative guess at the rate for pause-time
> 257:     // card refinement by one thread.
> 258:     const double rate_1 = 200.0; // cards/ms/thread

I would prefer if this magic number were placed somewhere more standing out than in some static method in a cpp file. I thought at least put it into the .hpp file as part of the `G1ConcurrentRefine" class. However there are no guidelines for that for g1 code where or how to collect these magic constants I'm kind of good with that too.

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Marked as reviewed by tschatzl (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6549