On Mon, 14 Sep 2020 05:08:39 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> Richard Reingruber has updated the pull request incrementally with one
>> additional commit since the last revision:
>>
>> Changes based on dholmes' feedback.
>>
>> EscapeBarrier::sync_and_suspend_all():
>>
>> - Set suspend flags before handshake because then the setting will be
>> visible
>> after leaving the _thread_blocked state in
>> JavaThread::wait_for_object_deoptimization()
>>
>> JavaThread::wait_for_object_deoptimization()
>>
>> - Reuse SpinYield instead of new custom spinning code.
>>
>> - Do safepoint check after the loop. This is possible because the
>> set_obj_deopt_flag is done before the handshake.
>>
>> - Don't set_suspend_equivalent() anymore for more simplicity. It's just
>> an
>> optimization (that won't pay off here).
>>
>> Added/updated source code comments.
>>
>> Additional smaller enhancements.
>
> src/hotspot/share/prims/whitebox.cpp line 884:
>
>> 882:
>> 883: WB_ENTRY(jboolean, WB_IsFrameDeoptimized(JNIEnv* env, jobject o, jint
>> depth))
>> 884: JavaThread* t = JavaThread::current();
>
> A WB_ENTRY is a JNI_ENTRY which means the current JavaThread is already
> available via the `thread` variable.
Done.
> src/hotspot/share/runtime/thread.cpp line 2660:
>
>> 2658: // showed 5% better performance when spinning.
>> 2659: if (should_spin_wait) {
>> 2660: // Inspired by HandshakeSpinYield
>
> Can we not reuse any existing spinning code in the VM?
Good point.
I wasn't aware of SpinYield. I use it now for the spinning.
I use 10 * SpinYield::default_spin_limit as spin limit based on
microbenchmarking:
http://cr.openjdk.java.net/~rrich/webrevs/8227745/pr116v2.microbenchmark/
-------------
PR: https://git.openjdk.java.net/jdk/pull/119
