[External] : Re: : Re: JEP 475 is now open for porting

Tue Jun 18 09:05:03 UTC 2024

> Sure, actually this was followed in past as well; But I got confused by seeing different JBS issues for each port;

Ah, I see how that could lead to confusion. I just added a note to the porting JBS issues clarifying their purpose.

Thanks,

Roberto

________________________________________
From: Amit Kumar <Amit.Kumar220 at ibm.com>
Sent: Tuesday, June 18, 2024 3:00 AM
To: Roberto Castaneda Lozano
Cc: Amit Kumar; porters-dev at openjdk.org; boris.ulasevich at bell-sw.com; snazarkin at azul.com; Martin Doerr; yangfei at iscas.ac.cn; shipilev at amazon.de
Subject: [External] : Re:  : Re:  JEP 475 is now open for porting

Our suggested way forward is to gather all platform ports into the PR and integrate the whole JEP implementation (that is, including support for all platforms) atomically into mainline, within the JDK 24 development phase. We understand that porting the JEP is a non-trivial task and are happy to wait for the ports before integrating into mainline, as long as there is a commitment to contribute them within JDK 24.

Sure, actually this was followed in past as well; But I got confused by seeing different JBS issues for each port;

Thanks for the explanation,
Amit Kumar

On 18 Jun 2024, at 1:33 AM, Roberto Castaneda Lozano <roberto.castaneda.lozano at oracle.com> wrote:

Hi Amit, see my replies inlined below.

The build is broken with these changes.

Yes, the build is broken in the current PR for platforms missing late barrier support for G1. This is the expected initial state of the PR.

Are you gonna wait until We all finish the Ports ? Are we gonna integrate our changes before this change merges so that we don’t face a build break ?

Our suggested way forward is to gather all platform ports into the PR and integrate the whole JEP implementation (that is, including support for all platforms) atomically into mainline, within the JDK 24 development phase. We understand that porting the JEP is a non-trivial task and are happy to wait for the ports before integrating into mainline, as long as there is a commitment to contribute them within JDK 24.

Is there a flag to turn it off completely? I tried to look into src/hotspot/share/gc/g1/g1_globals.hpp and surprisingly it didn’t work.

The PR includes a *temporary* JVM flag (G1UseLateBarrierExpansion) to choose between early (the current model) and late barrier expansion, as an aid to develop the port. To use it, you need to enable the preprocessor flag G1_LATE_BARRIER_MIGRATION_SUPPORT first, and possibly fix some trivial build errors. Please let me know if you face further issues. Note that this flag (and all code conditionally compiled under G1_LATE_BARRIER_MIGRATION_SUPPORT) is temporary support for the task of porting the JEP, and will be excluded from the final PR. To quote the JEP description: "it is not a goal to retain G1's current early barrier expansion as a legacy mode".

Hope this clarifies your questions!

Thanks,

Roberto

________________________________________
From: Amit Kumar <Amit.Kumar220 at ibm.com<mailto:Amit.Kumar220 at ibm.com>>
Sent: Monday, June 17, 2024 6:58 PM
To: Roberto Castaneda Lozano
Cc: Amit Kumar; porters-dev at openjdk.org<mailto:porters-dev at openjdk.org>; boris.ulasevich at bell-sw.com<mailto:boris.ulasevich at bell-sw.com>; snazarkin at azul.com<mailto:snazarkin at azul.com>; Martin Doerr; yangfei at iscas.ac.cn<mailto:yangfei at iscas.ac.cn>; shipilev at amazon.de<mailto:shipilev at amazon.de>
Subject: [External] : Re:  JEP 475 is now open for porting

Hi Roberto,

I just want to understand how this is gonna move forward. The build is broken with these changes.

Are you gonna wait until We all finish the Ports ?
Are we gonna integrate our changes before this change merges so that we don’t face a build break ?
Is there a flag to turn it off completely? I tried to look into src/hotspot/share/gc/g1/g1_globals.hpp and surprisingly it didn’t work.

Thanks,
Amit Kumar

On 17 Jun 2024, at 6:03 PM, Roberto Castaneda Lozano <roberto.castaneda.lozano at oracle.com> wrote:

Hi all,

The implementation of JEP 475 (platform-independent changes and x64 and aarch64 support) is now available for reviews and porting to the remaining platforms:

https://github.com/openjdk/jdk/pull/19746<https://urldefense.com/v3/__https://github.com/openjdk/jdk/pull/19746__;!!ACWV5N9M2RV99hQ!KavqzF_KaNHEb6RXpBij5lez1P8moqpShz_zNLE_3KAVuKmmTstHzQsEFk4jTnPZ9Xv-QHBMZC29kAcX5jrhMc9lJVjgeSiTNg$>

I have created the following JBS tasks to track the progress of each individual port:

- arm (32-bit): https://bugs.openjdk.org/browse/JDK-8334110
- ppc: https://bugs.openjdk.org/browse/JDK-8334111
- riscv: https://bugs.openjdk.org/browse/JDK-8334112
- s390: https://bugs.openjdk.org/browse/JDK-8334113
- x86 (32-bit): https://bugs.openjdk.org/browse/JDK-8334115

I am happy to answer questions about porting the JEP and offer further guidance if necessary. Thank you all in advance for your collaboration!

Roberto Castañeda Lozano (HotSpot compiler team at Oracle)