Backport cgroups v2 to 8u

[Jonathan Dowland]

Hi Poonam,

On Tue, Oct 04, 2022 at 08:52:14PM +0000, Poonam Parhar wrote:
>We, Oracle, are in the process of backporting a bunch of cgroups v2 fixes to Oracle jdk8u.

Great to hear!

> We have started with backporting the following 6 issues first.
>
>1. JDK-8230305: Cgroups v2: Container awareness
>2. JDK-8231111: Cgroups v2: Rework Metrics in java.base so as to recognize unified hierarchy
>3. JDK-8253714: [cgroups v2] Soft memory limit incorrectly using memory.high
>4. JDK-8237479: 8230305 causes slowdebug build failure
>5. JDK-8253727: [cgroups v2] Memory and swap limits reported incorrectly
>6. JDK-8278951: containers/cgroup/PlainRead.java fails on Ubuntu 21.10

>I see that Jonathan Dowland has already submitted PRs to jdk8u-dev for the first 2 issues.

I've only just seen your mail. I've so far done 1, 2, 3, 4, but not 5
and 6.

>I think we can collaborate our efforts here. In a few days, we will be
>completing our work on backporting the above fixes to Oracle jdk8u.
>After that, we can contribute the changes for the remaining four issues
>to jdk8u-dev. Please let me know your thoughts.

Severin has shared the "hit list" of things we think should be
backported, which is largely in the order they need to happen. Please
point out if there's anything missing, or out of order.

Where possible, I've been using Skara's "dependent PR" support to chain
the PRs together: so for example pr/128 (8237479) depends upon pr/127
(8230305).

I've had to make some of the PRs artificially depend on others, in order
to flatten out multiple-dependencies: so pr/127 (8230305) depends upon
pr/121 (8231111) even though the patches do not, but that's to support
pr/130 (8253714) depending on both.

To avoid us repeating each other's work, how about we use the jdk8u
convention of labelling bugs in progress with jdk8u-<name>? E.g.
jdk8u-jdowland in my case.

I don't think any review work has started, and I haven't done heavy test
runs for any of the existing PRs yet.


Best wishes,

-- 
👱🏻 Jonathan Dowland <jdowland at redhat.com>
Senior Software Engineer, OpenJDK, Red Hat