Spin Loop Hint support: Draft JEP proposal

Andrew Haley aph at redhat.com
Thu Oct 8 09:28:15 UTC 2015

On 10/07/2015 09:21 PM, Gil Tene wrote:
> Interesting. I was going off of the 32 bit ARM documentation. Looks like
> ARMv8 improved on that, and did it implicitly (without requiring different
> instructions).
> You can see the differences on the unlock path between the 32 bit and 64 bit implementations here:
> http://lxr.free-electrons.com/source/arch/arm/include/asm/spinlock.h
> http://lxr.free-electrons.com/source/arch/arm64/include/asm/spinlock.h

Yeah, that's right.  SEV is very broadcasty and not at all suited to
large systems, which is obviously what v8 is aimed at.

There are also local timer queues, BTW, and one of the things a timer
can do is a local SEV.  So we have just the right things, if we can
ever figure out how to use them in Java!

BTW, I apologize for hijacking your thread.  Your JEP looks good, and
I can't see any good reason that such a simple and non-intrusive API
shouldn't go in.


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