RFR: Add support for CollectedHeap::get_safepoint_workers()

[Per Liden]

Thanks Erik!

/Per

On 05/08/2018 05:08 PM, Erik Österlund wrote:
> Hi Per,
> 
> Looks good.
> 
> Thanks,
> /Erik
> 
> On 2018-05-08 16:49, Per Liden wrote:
>> Added support for CollectedHeap::get_safepoint_workers(), to reduce 
>> safepoint cleanup times.
>>
>> http://cr.openjdk.java.net/~pliden/zgc/get_safepoint_workers/webrev.0
>>
>> Here are some numbers on from SPECjbb2015, which look encouraging.
>>
>> Before:
>>
>> Safepoint cleanup tasks (secs):
>>                 avg: 0.00286622 (+/-0.00189263)
>>     95th percentile: 0.0059704
>>     99th percentile: 0.006819
>>   99.9th percentile: 0.0089186
>>  99.99th percentile: 0.0117573
>>                 max: 0.0117573
>>
>> After:
>>
>> Safepoint cleanup tasks (secs):
>>                 avg: 0.000676487 (+/-0.000212009)
>>     95th percentile: 0.0010262
>>     99th percentile: 0.0011429
>>   99.9th percentile: 0.0012933
>>  99.99th percentile: 0.0013363
>>                 max: 0.0013363
>>
>> /Per
>