Why is my workload not behaving better with gen-zgc?

[Ragnar Rova]

Hello!

Unsure if this is the right place to ask, but the gen-zgc page did ask
for feedback, so here goes:

I have a workload that is performing worse latency-wise when measuring
actual service response times compared to G1, both P99 all the way
down to P50 as measured in a short 5-minute load test. Benchmark was
run on aarch64 on MacOS using 21-genzgc+1-8.

I have benchmarked this workload before on OpenJDK 19 using stock ZGC
and also here G1 performs better. My speculation was that ZGC
performed worse due to the generational nature of the allocations my
workload has. But, when recently testing 21-genzgc+1-8, G1 still
outperforms in terms of both throughput (that was expected) and
latency profile (less so).

What kind of measurements would be needed to discuss this?

Attaching gc logs for a 5-minute benchmark run if that is helpful for
genzgc and G1 from the same JDK build.
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