[master] RFR: Smaller class pointers [v2]

[Thomas Stuefe]

On Tue, 7 Dec 2021 07:38:07 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> > @iklam already had an off-list look at the changes with his CDS eyes.
> 
> I looked at the CDS code and it looks fine to me. Just a small nit.
> 
> BTW, do you have size comparison of the CDS archive before/after?
> 
> Thanks
> 
> * Ioi

Sure, here you go:


-- Archive file --

before:

classes.jsa		13434880
classes_nocoops.jsa 	12279808

after:

classes.jsa		13783040  (+348k, +2.5%)
classes_nocoops.jsa 	12623872  (+344k, +2.8%)

-- Runtime costs --

before:

-        Shared class space (reserved=12582912, committed=12247040)
                            (mmap: reserved=12582912, committed=12247040)

after:

-        Shared class space (reserved=16777216, committed=12591104)
                            (mmap: reserved=16777216, committed=12591104)
                            
committed runtime costs: +344k

Reserved cost higher since, I assume, the size estimation to prepare mapping the archive is higher since we always add the full alignment cost when estimating the size before mapping.

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PR: https://git.openjdk.java.net/lilliput/pull/13