Switch to FxHasher hash function in bitmix - 3s faster building sys image #53844
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This reverts commit 62d5814.
This reverts commit 841185a. Using bitmix is incorrect, as on 64 bit systems bitmix uses the 64 bit version of FxHasher. Also possibly a performance regression.
This reverts commit 80ee622. We have a perf regression since first commit, I've had trouble getting reliable benchmarking results so reverting this in case this caused a regression.
Co-authored-by: Stefan Karpinski <stefan@karpinski.org>
This reverts commit dd4c2f6.
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@Zentrik Should we run some benchmarks on this PR? |
| #ifdef _P64 | ||
| STATIC_INLINE uint64_t bitmix(uint64_t a, uint64_t b) JL_NOTSAFEPOINT | ||
| { | ||
| return int64hash(a^bswap_64(b)); |
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Is bswap_64 still needed after this PR, or it can be removed?
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I don't see it referenced elsewhere so I guess so
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There is a downside to this that objectid is no longer a (mostly) unique identifier for a given object type in a given session, so if it isn't faster, it might not be worth doing |
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Why is this different from whatever hash we use right now? Isn't it just switching one hash function to another? |
I'm fairly skeptical the improvement will be discernible from the noise for nanosoldier. Unfortunately, it's going to be a while before we can get instruction counts from nanosoldier. |
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So I don't forget if I ever come back to this: looks like fxhasher was made a bit faster with rust-lang/rustc-hash@177c566. |
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make cleanall; make, buildingcorecompiler.jinow takes 205-206s whilst on 4a2c593 it took 208-210s.On the allinference benchmarks in BaseBenchmarks I see a 0.5-1% improvement in instruction counts.
This is an updated version of #52496.
I recall someone sharing a profile of building Julia on the slack a while ago, if they still have it could I see which functions were calling inthash/int64hash the most.