Odd decrease of benchmark throughput

[Aleksey Shipilev]

On 09/06/2016 01:05 PM, Dávid Karnok wrote:
> # Run progress: 16,67% complete, ETA 00:01:47
> # Fork: 1 of 1
> # Warmup Iteration   1: 622,250 ops/s
> # Warmup Iteration   2: 646,154 ops/s
> # Warmup Iteration   3: 637,035 ops/s
> # Warmup Iteration   4: 639,014 ops/s
> # Warmup Iteration   5: 645,212 ops/s
> Iteration   1: 648,120 ops/s
> Iteration   2: 647,042 ops/s
> Iteration   3: 650,176 ops/s
> Iteration   4: 335,979 ops/s
> Iteration   5: 195,415 ops/s
> 
> (Running Windows 7 x64, Java 8u102, i7 4790)
> 
> Please advise.

We have seen the behavior like that before.

The way to further diagnose this: prepare two runs where measurement
phase a) has only 650 ops/s iterations; b) has only 195 ops/s iterations
-- vary warmup/measurement durations to fit. After that, -prof perfasm
both runs and see where the difference in profiles is. perfasm takes
only the measurement phase in the consideration.

99% bet is on different compilation, and it is important to know what
exactly compiled differently in 195 ops/sec iterations.

Thanks,
-Aleksey