RFR: 8276796: gc/TestSystemGC.java large pages subtest fails with ZGC

[Stefan Karlsson]

On Tue, 9 Nov 2021 12:09:00 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> ZGC would not start when it cannot allocate the heap with `-XX:+UseLargePages`. This makes the `UseLargePages` subtest fail on systems with (default) `nr_hugepages = 0`. It was exposed after [JDK-8269077](https://bugs.openjdk.java.net/browse/JDK-8269077) moved that test config from G1-specific to generic one.
> 
> While fixing this bug, I decided to massage a test a bit: make it consistently choosing the configuration based on GC availability, doing `UseLargePages` tests only for GCs that fall back to non-large pages if not available, added test IDs. This basically goes the other way JDK-8269077 went: put in the GC-specific configs.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug, `gc/TestSystemGC.java` (runs all 5 configs)
>  - [x] Linux x86_64 fastdebug, `gc/TestSystemGC.java`, `TEST_VM_OPTS=-XX:+UseSerialGC` (runs 1 config)
>  - [x] Linux x86_64 fastdebug, `gc/TestSystemGC.java`, `TEST_VM_OPTS=-XX:+UseParallelGC` (runs 1 config)
>  - [x] Linux x86_64 fastdebug, `gc/TestSystemGC.java`, `TEST_VM_OPTS=-XX:+UseG1GC` (runs 1 config)
>  - [x] Linux x86_64 fastdebug, `gc/TestSystemGC.java`, `TEST_VM_OPTS=-XX:+UseShenandoahGC` (runs 1 config)
>  - [x] Linux x86_64 fastdebug, `gc/TestSystemGC.java`, `TEST_VM_OPTS=-XX:+UseZGC` (runs 1 config)

Looks like a sensible fix.

test/hotspot/jtreg/gc/TestSystemGC.java line 27:

> 25: 
> 26: /*
> 27:  * @test id=serial

In recent changes we used upper-case for the id labels. I think it would be good to be consistent and do the same here.

test/hotspot/jtreg/gc/TestSystemGC.java line 63:

> 61:  * @test id=z
> 62:  * @requires vm.gc.Z
> 63:  * @comment ZGC would not start when LargePages cannot be allocated, therefore

Maybe replace "ZGC would not" to "ZGC will not"?

-------------

Changes requested by stefank (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6310