[11u] RFC: Update Graal in OpenJDK 11 Updates?

[Andrew Dinn]

Hi Doug,

On 23/03/2020 13:36, Doug Simon wrote:
> Sorry, this thread is long and has mentioned a number of patches.
> Which ones are you referring to here?

The specific changes in question were derived from the discussion in
github/graal issue #2196. The patches are detailed in the 2 webrevs
Christoph posted:

  http://cr.openjdk.java.net/~clanger/webrevs/8208686.11u/

and

  http://cr.openjdk.java.net/~clanger/webrevs/graal13.11u/

The first webrev is the fix for JDK-8208686. The second one is
essentially the bundled update that Tom pushed to the labs version of
jkd11u after Christoph tweaked ti to make it apply and build correctly.

> I’m having trouble parsing that question. Are you asking “is there
> anything in GitHub Graal that depends on the JVMCI changes in
> labs-openjdk-11”?

I am asking two things:

1) Is there anything in the current GitHub Graal repo that critically
depends on the above changes getting into jdk11u?

2) Is there anything planned for addition to the GitHub Graal repo that
critically depends on the above changes getting into jdk11u?

In other words why do this backport instead of just use the current jdk11u?

> I believe Tom has previously provided a breakdown of the patches in
> labs-openjdk-11. Everything in labs-openjdk-11 is essential for
> supporting complete GraalVM functionality as far as I understand
> otherwise it would not be there.

First, I think all the patches mentioned in that list that involve
hotspot changes have been backported except for the ones listed above --
which is why we are currently able to build GraalVM using the latest
OpenJDK jdkd11u.

Now, I'm not suggesting that there is any /redundancy/ as regards these
remaining patches. However, what we would like to know is why we need to
backport them i.e. what problem do they resolve and what would be the
upshot if we stop further backports where we are now.

The existing jdk11u code appears to work to build Graal VM. It also
works perfectly well to build and run the in-tree Graal code. So, by
'upshot' above I mean what would it imply for the ability to continue
using jdk11u to build Graal if we don't backport the above changes? This
is one side of a benefits equation we need to assess.

> I think the high order point is that porting the changes in
> labs-openjdk-11 to jdk11u is going to be complex due the way we
> back-ported changes from JDK 13. With more time, we would have tried
> to be more principled about it but on the other hand we were keen to
> release GraalVM on JDK 11 given how much demand there was for it.

Yes, I had noticed that ;-). Also, I fully understand why a mega-patch
was chosen at the time (especially since Red Hat were responsible for a
lot of the demand you mention). I'm really trying to assess the degree
to which we can justify bringing jdk11u up to date with the jdk13u base
level.

> It might help to have a Zoom call to discuss this further. I want Tom
> to be on the call so some time between 18:00 - 21:00 CET would
> probably work. I can do any day except Tuesday.

Well, we normally try very hard to keep discussions like this in public
so that they are visible to all who might have an interest and also on
record. It's not really good open source practice to do otherwise.
However, I'd be happy to try to use the tech to help expedite resolution
of this issue -- so long as we report back ideas, suggestions and
conclusions here to all interested parties. That's also assuming that
others are happy to join in. Perhaps anyone interested in taking up your
offer could respond and then we can take arrangement of a Zoom call offline.

regards,


Andrew Dinn
-----------
Senior Principal Software Engineer
Red Hat UK Ltd
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