RFR: 8307958: Metaspace verification is slow causing extreme class unloading times [v2]

[Coleen Phillimore]

On Tue, 23 May 2023 08:04:23 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> Maybe it is overly defensive to add it to the split and get_chunk paths. The observed slowdown was for purge() calls, and more specifically the verification downstream of ~MetaspaceArena(), which includes return_chunk and merge() as well as freelist contains() verification.

Ok, thanks for the info.  That makes sense.

I thought there were more GC tests for class unloading but I can't find them.  If you create one test with loading/unloading a class 100 times with the SOMETIMES verification on, I think that would run fast enough and exercise the code paths that won't be exercised regularly.  You can put it in runtime/ClassUnload with some other tests.  Or if you can find tests already in metaspace that do this, that would be sufficient.

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PR Comment: https://git.openjdk.org/jdk/pull/14084#issuecomment-1559151947