RFR: JDK-8199620: Support for JNI object pinning (original) (raw)

White, Derek Derek.White at cavium.com
Wed Mar 14 22:22:07 UTC 2018

Hi Roman,

Interesting idea.

Is the intention to NOT call GCLocker::lock_critical() in the case when the object can be pinned?

I can see how this allows pinning a region, but I don't see in this webrev where we’re getting any benefit.

Thanks!

-----Original Message----- From: hotspot-gc-dev [mailto:hotspot-gc-dev-bounces at openjdk.java.net] On Behalf Of Roman Kennke Sent: Wednesday, March 14, 2018 2:51 PM To: hotspot-gc-dev at openjdk.java.net Subject: Re: RFR: JDK-8199620: Support for JNI object pinning

Am 14.03.2018 um 19:13 schrieb Roman Kennke: > Currently, the Get/Release*Critical() family of functions use the > GCLocker protocol to ensure that no JNI critical arrays are in use > when a GC pause is entered. > > Some GCs may instead want to use object pinning and guarantee that the > object does not move. For example, this is easy to do with > region-based GCs (G1, Shenandoah, ZGC) by simply not including regions > with pinned objects in the collection set. > > The implementation/API that I'm proposing is fairly simple: add two > methods oop pinobject(oop) and void unpinobject(oop) to > CollectedHeap, and call them from JNI's Get/Release*Critical methods. > > This approach has been working perfectly fine since a long time in > Shenandoah. > > Bug: > https://bugs.openjdk.java.net/browse/JDK-8199620 > Webrev: > http://cr.openjdk.java.net/~rkennke/8199620/webrev.00/ And here is the correct patch: http://cr.openjdk.java.net/~rkennke/8199620/webrev.01/ Roman

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