Troubles with Shenandoah

[Roman Kennke]

> On Mon, Apr 8, 2019 at 9:28 PM Aleksey Shipilev <shade at redhat.com>
> wrote:
> > Yes. Here's a taste when nothing else is happening, and only memory
> > commit is done:
> > 
> > $ time java -Xms100g -Xmx100g -XX:+AlwaysPreTouch -XX:+UseSerialGC
> > -version
> > openjdk version "13-internal" 2019-09-17
> > OpenJDK Runtime Environment (build 13-internal+0-adhoc.shade.jdk-
> > jdk)
> > OpenJDK 64-Bit Server VM (build 13-internal+0-adhoc.shade.jdk-jdk,
> > mixed mode)
> > 
> > real    0m33.461s
> > user    0m4.733s
> > sys     0m28.600s
> > 
> > ...when other things happen concurrently, the whole thing might
> > take a while to satisfy even a small
> > one-off request.
> 
> Holy cow!
> 
> > Yes. Just don't be surprised when concurrent collectors do not give
> > the latency boost there :)
> 
> I'm not expecting a median latency boost here.
> I actually had no expectations and was just curious as to what could
> have happened when running the CometD benchmark with ZGC and
> Shenandoah.
> 
> But we have people interested in reducing max latency as much as
> possible, even sacrificing some throughput and median latency, so ZGC
> and Shenandoah are worth exploring.
> We (as the Jetty team) take the hit of trying these new GCs early so
> at least we have some knowledge when people ask us about them :)
> 


Good thing: it did uncover some bugs, even though not related to your
original request:
https://bugs.openjdk.java.net/browse/JDK-8222125
https://bugs.openjdk.java.net/browse/JDK-8222129

then we see a crash in C2 compiler when running the client with
Shenandoah.

Plus the crash that you observed with jdk12.

I call that a win :-)

Roman