Removing intrinsic of Thread.isInterrupted() (original) (raw)

Karen Kinnear karen.kinnear at oracle.com
Tue Feb 25 10:23:07 PST 2014

Performance team folks -

I think it would be very helpful to identify any "real" benchmarks, rather than a small hand-rolled micro-benchmark.

Compiler folks -

Does anyone have the history of why this instrinsic was added? And what benchmark(s) that was for?

I think it would help to get current data on those benchmarks or more recent versions of them please.

thanks, Karen

On Feb 25, 2014, at 1:05 PM, Aleksey Shipilev wrote:

Hi Yumin,

On 02/25/2014 09:25 PM, Yumin Qi wrote: Thanks for the info, I modified as Ok, if you still wish to go for hand-rolled benchmarks:

final int NUM = 20000; boolean interrupts[] = new boolean[NUM]; start = System.currentTimeMillis(); for (int j = 0; j < 100; j++) { for (int i = 0; i < NUM; i++) { interrupts[i] = t.isInterrupted(); } } finish = System.currentTimeMillis(); osum = finish - start; System.out.println(NUM + " calls cost: " + osum + " ms"); So, this benchmark still suffers from: * The absence of warmup * Dead-code elimination of interrupts[] accesses, and the elimination of t.isInterrupted as the result. * System.currentTimeMillis() (high) granularity * Loop unrolling for both "i" and "j" loops, further affected by the presence of inlined code for isInterrupted, or native call stub * Possible hoisting of t.isInterrupted() from the loop (native methods should be immune, and I remember there should be the barrier in the intrinsic to prevent that) The result showed no difference (even a little better without intrinsic). ...and that begs the question, right? Why does it happen? Why the performance is similar for seemingly different code paths? Is intrinsic not working whatsoever? Is the experiment correct? Do we actually measure it right, etc? I think I can remove it from hotspot. I don't think we can, until we understand the performance implications through and through. Thanks, -Aleksey.

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