RFR: Remove CSetThreshold handling from heuristics

[Roman Kennke]

Am 05.04.2018 um 15:50 schrieb Aleksey Shipilev:
> Ping?
> 
> On 04/04/2018 07:57 PM, Aleksey Shipilev wrote:
>> http://cr.openjdk.java.net/~shade/shenandoah/purge-cset-threshold/webrev.01
>>
>> We did this thing before separate UR phase was introduced. The role for this threshold was to avoid
>> double-cycle when heuristics thinks the free space hoarded in cset is not available. However, it is
>> not fully reliable: the fact that we "appear" to have more free space than we actually have risks to
>> run into alloc-failure during late mark. Also, since separate UR phase is enabled, we don't even
>> care about double-cycle issue anymore: CM-with-UR cycles _are_ back-to-back.
>>
>> Removing this simplifies the code.
>>
>> Testing: hotspot_gc_shenandoah, SPECjbb (where the original double-cycle was observed)
>>
>> Thanks,
>> -Aleksey
>>
> 

Have you checked that the double-cycle issue does not occur? E.g. in
visualizer?

Otherwise sounds reasonable and patch looks good. Thanks!

Roman