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

[Per Liden]

Hi,

Please note that backporting JDK-8224675 "Late GC barrier insertion for 
ZGC" is not great idea, since that patch introduced stability issues and 
the whole approach was later superseded by JDK-8230565 "ZGC: Redesign C2 
load barrier to expand on the MachNode level".

If you want to go down this path, I'd suggest that you either don't 
backport JDK-8224675 at all, or backport everything up to JDK-8224675 + 
JDK-8230565. Also note that if you include JDK-8230565 you want to be 
careful to also include any followup bug fixes, like JDK-8233506.

In general, a lot of stability and performance improvements have gone 
into ZGC since JDK 11. If at all possible, I would strongly recommend 
using JDK 14 instead, where you already have aarch64 support and all 
other goodies.

cheers,
Per

On 1/15/20 7:58 AM, Yangfei (Felix) 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
>