Uploaded image for project: 'JDK'
  1. JDK
  2. JDK-8269230

C2: main loop in micro benchmark never executed

    XMLWordPrintable

    Details

    • Subcomponent:
    • Resolved In Build:
      b30

      Backports

        Description

        The attached benchmark has interesting results:

        ```
        Benchmark (size) Mode Cnt Score Error Units
        TestLoadBytes.arrayScalar 1024 avgt 10 241.256 ? 1.028 ns/op
        TestLoadBytes.arrayScalarConst 1024 avgt 10 244.251 ? 5.218 ns/op
        TestLoadBytes.bufferNativeScalar 1024 avgt 10 262.128 ? 1.251 ns/op
        TestLoadBytes.bufferNativeScalarConst 1024 avgt 10 250.552 ? 2.710 ns/op
        TestLoadBytes.segmentNativeScalar 1024 avgt 10 722.670 ? 6.427 ns/op
        TestLoadBytes.segmentNativeScalarConst 1024 avgt 10 253.419 ? 3.043 ns/op
        ```

        Access using segment is almost 4x slower than using byte buffers. When investigating the generated compiled code, it seems like all the time is spent in the post-loop, and that the main loop (which seems to unroll correctly) is never executed.

          Attachments

            Issue Links

              Activity

                People

                Assignee:
                roland Roland Westrelin
                Reporter:
                mcimadamore Maurizio Cimadamore
                Votes:
                0 Vote for this issue
                Watchers:
                5 Start watching this issue

                  Dates

                  Created:
                  Updated:
                  Resolved: