Could we get rid of the UseCompressedClasses switch altogether, defaulting to const true?

[Thomas Stüfe]

Greetings,

Are there any realistic scenarios that would require
UseCompressedClassPointers=false? Or could we make it constant at some
point or remove the switch altogether?

The only reason I can see for UseCompressedClassPointers=off would be if
the maximum class space size of 3GB is not enough. But how realistic is
this really? Some numbers:

On average, a Klass is ~600-700 bytes. Therefore, 3GB of class space would
be enough for ~5 million classes. Note that the typical size ratio of
Klass-to-non-class-metadata is 1:6 .. 1:10, which means that 3 GB class
space come with ~18..30 GB of non-class metaspace (see [1]). I think these
are outlandish numbers. Do we need to support these scenarios? Some weird
class generator scenarios maybe?

Other than class space max size not being enough, are there any reasons for
-UseCompressedClassPointers?

Thank you,

Thomas

[1]
https://github.com/tstuefe/metaspace-statistics/blob/master/Histogram.svg
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