[master] Integrated: Trim identity-hashcode to 25bit
rkennke at openjdk.java.net
Tue May 11 17:16:48 UTC 2021
On Mon, 10 May 2021 17:08:02 GMT, Roman Kennke <rkennke at openjdk.org> wrote:
> I'd like to trim the identity hashcode to 25 bits to make room in the upper 32bits for the compressed class-pointer.
> This could in theory regress performance on workloads that make heavy use of i-hashes, but I could not show this in practice (by specjvm workloads like compiler which uses lots of ihashes).
> Next step would be to move the Klass* into the upper 32bit part. (If you look closely, this would be the exact header layout of 32bit JVMs.) And then get rid of the dedicated Klass* field. :-D Eventually I'd make ihash-bits and klass* bits configurable to trade one for the other.
> - [x] some manual benchmarks
> - [x] tier1
> - [ ] tier2
This pull request has now been integrated.
Author: Roman Kennke <rkennke at openjdk.org>
Stats: 16 lines in 3 files changed: 6 ins; 2 del; 8 mod
Trim identity-hashcode to 25bit
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