On Thu, 20 Jul 2023 15:55:18 GMT, Glavo <d...@openjdk.org> wrote: >>> In this result, ByteBuffer is much slower than VarHandle. Am I doing >>> something wrong? What conditions are needed to make the performance of >>> ByteBuffer close to that of Unsafe? >> >> These are some benchmarks we have in the JDK: >> >> Off-heap access: >> >> >> Benchmark Mode Cnt Score Error Units >> LoopOverNonConstant.BB_get avgt 30 3.837 ± 0.045 ns/op >> LoopOverNonConstant.unsafe_get avgt 30 3.425 ± 0.032 ns/op >> >> >> On-heap access: >> >> >> Benchmark (polluteProfile) Mode Cnt Score >> Error Units >> LoopOverNonConstantHeap.BB_get false avgt 30 3.897 ± >> 0.055 ns/op >> LoopOverNonConstantHeap.unsafe_get false avgt 30 3.446 ± >> 0.027 ns/op >> >> >> BB is almost on par with unsafe. There's of course an extra bound check >> which you pay for. These benchmark are almost idential to the one you >> shared, so not sure what's going on. > > @mcimadamore I ran a series of experiments. When `ByteBuffer` is only used as > a local variable without escaping, it is very close to `VarHandle`(`Unsafe`). > However, any attempt to put the `ByteBuffer` into a field (even a static > final field) resulted in the throughput drop of more than 50%.
I just ran your benchmark above - which is similar as I said to the ones we already have in the JDK. Results: Benchmark Mode Cnt Score Error Units ByteArray.readByte avgt 30 3.619 ± 0.051 ns/op ByteArray.readByteFromBuffer avgt 30 3.936 ± 0.071 ns/op ByteArray.readInt avgt 30 3.653 ± 0.054 ns/op ByteArray.readIntFromBuffer avgt 30 3.798 ± 0.019 ns/op ByteArray.readLong avgt 30 3.637 ± 0.053 ns/op ByteArray.readLongFromBuffer avgt 30 3.922 ± 0.012 ns/op I don't see 2x slowdown. Which JDK are you using? Which platform? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14636#discussion_r1269675593
