Increased safepoint cleanup tasks in Java 11 (vs 8)

[Vitaly Davidovich]

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.

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