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

[Kim Barrett]

On Tue, 30 Nov 2021 10:26:20 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> 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.
>
> I agree with Thomas. I think this should live in `G1ConcurrentRefine`, but if you don't agree I'm ok with leaving as is.

Moving it into the class would have required moving the referencing static
function into the class, &etc. I've given it a more informative name and
description, and moved it to file scope to make it more prominent.

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