On 2020-05-06 16:59, Claes Redestad wrote:
-XX:TieredStopAtLevel=1: Benchmark Mode Cnt Score Error Units 15-b19 Capture0.lambda_01 avgt 5 6.312 ± 0.919 ns/op 15-b20 Capture0.lambda_01 avgt 5 105.761 ± 7.575 ns/op jdk Capture0.lambda_01 avgt 5 105.228 ± 7.175 ns/op So outside of the direct bootstrap improvement, there's a positive effect during early warmup. Sadly this patch doesn't translate into an improvement in C1. I can see a rather large regression in C1 on this specific micro in 15-b20 (which is where the Hidden Classes integration happened).
Filed: https://bugs.openjdk.java.net/browse/JDK-8244550 Overhead is entirely in Unsafe::allocateInstance, which will be intrinsified by C2, but has ~100ns/op overhead when called from interpreter and C1 code. I've prototyped a patch to remove a few redundant VM->native transitions and gotten this overhead down to 60ns/op. /Claes
