Increased safepoint cleanup tasks in Java 11 (vs 8)

[Robbin Ehn]

On 6/5/19 2:58 PM, Vitaly Davidovich wrote:
> Hey Aleksey,
> 
> On Wed, Jun 5, 2019 at 8:52 AM Aleksey Shipilev <shade at redhat.com> wrote:
> 
>> On 6/5/19 2:33 PM, Vitaly Davidovich wrote:
>>> Does anyone have ideas on pinpointing this further?
>>
>> I have the educated guess:
>>    https://bugs.openjdk.java.net/browse/JDK-8181859
>>
>> Which means you can try if -XX:MonitorUsedDeflationThreshold=0 reduces the
>> number of "guaranteed"
>> safepoints.
>>
> Hmm, the application doesn't use JVM monitors (in any meaningful
> capacity).  But interesting JBS entry - I will try it out, thanks! The
> description of safepoint clean up in there is/was consistent with my
> understanding as well.  On Java 8, we'd see the "no vm operation" safepoint
> operations, and I always assumed it was IC buffer cleaning (even had a mail
> thread on that topic a few years ago, either on this list or
> hotspot-compiler).  That tended to stabilize (i.e. they went away) after
> the application reached steady state, whereas I'm seeing essentially
> non-stop safepoint cleanups on 11.

Also note that this should be done outside of safepoints in the future:
https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2019-March/033267.html

/Robbin

> 
>>
>> --
>> Thanks,
>> -Aleksey
>>
>>