Spin Loop Hint support: Draft JEP proposal
aleksey.shipilev at oracle.com
Mon Oct 5 08:56:39 UTC 2015
Glad to see this being addressed!
On 10/04/2015 07:22 PM, Gil Tene wrote:
> We propose to add a method to the JDK which would be hint that a spin
> loop is being performed. E.g.
> jdk.util.PerformanceHints.spinLoopHint(), which will hopefully evolve
> to a Java SE API, e.g. java.util.PerformanceHints.spinLoopHint(). The
> specific name space location, class name, and method name will be
> determined as part of development of this JEP.
Yes, that would be a tough part. JDK is usually oblivious of these
low-level platform-specific hints, they go to sun.misc.* (e.g. Unsafe,
@Contended and others...). I'll let Project Leads to make that call :)
>  HotSpot WebRevs for prototype implementation which intrinsifies
* product_pd (platform-dependent) flags can be used to conditionalize
the support on a platform. This helps to avoid vm_version_* tricks.
* Does spinloophint imply membar as well? x86_64.ad suggests so.
library_call.cpp suggests so. It seems weird to conflate the two, even
though it's understandable you want to piggyback on existing machinery.
* I think spinLoopHint() misses a @HotspotIntrinsicCandidate annotation.
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