RFR: JDK-8240224 Allow building hotspot without the serial gc

[Aleksey Shipilev]

On 3/9/20 10:10 AM, David Holmes wrote:
> On 9/03/2020 6:30 pm, Magnus Ihse Bursie wrote:
>> When reworking the JVM feature handling, I wanted to try to compile 
>> Hotspot with various features enabled/disabled. I quickly found out that 
>> it's not really possible to build hotspot without the serial gc. While 
>> this is not a terribly important use case, I think it's good to be able 
>> to select serial freely, just as with the other collectors.
> 
> Really not sure this is a worthwhile exercise.

Me neither. I think Serial GC always-present is a good compromise for the rest of the code: it is
the very basic GC you can always count on.

Nits:

*) src/hotspot/share/gc/shared/gcConfig.cpp changes are a bit strange:
 - Epsilon should not ever be selected by ergonomics
 - Why ZGC is selected before Shenandoah? [Oh, what a can of worms that one is ;)]

*) hotspot/gtest/gc/shared/test_collectorPolicy.cpp
 - I don't think we indent nested #include, #define lines

-- 
Thanks,
-Aleksey