RFR (XXS): 8202829: Implement CollectedHeap::get_safepoint_workers() for G1
per.liden at oracle.com
Wed May 9 17:34:44 UTC 2018
Yep, looks good!
On 2018-05-09 18:52, Erik Osterlund wrote:
> Hi Thomas,
> A very beneficial one-liner indeed.
> Looks good!
>> On 9 May 2018, at 17:15, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
>> Hi all,
>> due to the recent RFR for ZGC I noticed that G1 would also benefit
>> from implementing CollectedHeap::get_safepoint_workers().
>> It is a pretty trivial change for G1 as we already have/use a "hot"
>> WorkGang that is always available during a safepoint.
>> Results from random specjbb2015 runs:
>> Baseline for "safepoint cleanup tasks":
>> count: 1628
>> min: 7.5e-05
>> max: 0.0072682
>> sum: 4.76701
>> avg: 0.00292814 (+/-0.0016433)
>> 95th percentile: 0.0054634
>> 99th percentile: 0.0062773
>> 99.9th percentile: 0.0072269
>> 99.99th percentile: 0.0072682
>> With changes for "safepoint cleanup tasks":
>> count: 1772
>> min: 9.24e-05
>> max: 0.0014651
>> sum: 1.33761
>> avg: 0.000754861 (+/-0.000230524)
>> 95th percentile: 0.0009985
>> 99th percentile: 0.001097
>> 99.9th percentile: 0.0012676
>> 99.99th percentile: 0.0014651
>> So, some significant improvement here, although very small in total.
>> Since it is such a simple change I guess we'll take it :)
>> I assume in the future the number of threads could be determined more
>> cleverly depending on actual work.
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