[aarch64-port-dev ] [RFC] ZGC proposal for aarch64 jdk11u

[Stuart Monteith]

Hello Felix,
     I'm pleased that there is interest in ZGC on aarch64, that the
performance is at expected levels and is apparently trouble free.
However, I'd like to understand why this backporting is being done. If
it is for running in production, then I'd expect Per, etc, to not be
upset or disagree when I that ZGC on aarch64 in JDK 13 isn't
production ready. I understand it would be easier to test with an
existing software stack on top of JDK 11 rather than moving onto JDK
13, etc. However, ZGC is an experimental VM feature, and the model
OpenJDK has moved to is for 6 monthly releases. Per and his team have
made lots of improvements, and fixes, in ZGC since 11, so I would
expect people to run and test on current release to avoid hitting
already known issues, whether that be on x86 or aarch64.

There might be a possibility of backporting some features, if there is
no effect when they are disabled. However, it is probably better to
track ZGC development through the released versions as a single
backport will not be enough, I wouldn't want to burden Per's team with
maintaining something that is in as much development as ZGC at this
point.

BR,
   Stuart

On Wed, 15 Jan 2020 at 06:59, Yangfei (Felix) <felix.yang at huawei.com> wrote:
>
> Hi,
>
> Currently, we only have zgc for the jdk11 x86 platform.  Zgc for aarch64 platform was later added in jdk13 by Stuart from Linaro.
> So it’s an interesting question whether zgc for aarch64 platform should be backported to jdk11.
>
>     Dozens of our arm-based cloud customers are switching to jdk11 and some of them have a strong demand for the zgc feature for their business.
> To satisfy that requirement, we took the action to backport this feature in our jdk11 release.
> But we think this work should not be kept private.  Other jdk11 vendors may come to the same problem.
> It’s appreciated if this work could be incorporated in the upstream jdk11 repo and further improved.
>
>     We have backported the following zgc related patches to jdk11u:
> https://bugs.openjdk.java.net/browse/JDK-8217745
> https://bugs.openjdk.java.net/browse/JDK-8224187
> https://bugs.openjdk.java.net/browse/JDK-8214527
> https://bugs.openjdk.java.net/browse/JDK-8224675<javascript:;>
>
>    Basic test such as jtreg, jcstress looks good.  Specjbb2015 test with zgc gives us anticipated max & critical score.
>     I can provide more details and propose a webrev for the backport.  But before that I would like to hear your comments & suggestions.
>
> Thanks,
> Felix