[master] RFR: Trim identity-hashcode to 25bit
rkennke at openjdk.java.net
Mon May 10 17:15:16 UTC 2021
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
- Trim identity-hashcode to 25bit
Stats: 15 lines in 2 files changed: 6 ins; 2 del; 7 mod
Fetch: git fetch https://git.openjdk.java.net/lilliput pull/3/head:pull/3
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