RFR: 8221732: Introduce CollectedHeap::hash_oop()
Stefan Karlsson
stefan.karlsson at oracle.com
Mon Apr 1 11:04:01 UTC 2019
Looks good.
StefanK
On 2019-04-01 09:39, Per Liden wrote:
> The JVMTITagMap hashes oops by casts them to 32-bit unsigned integers.
> For ZGC, which has colored oop, this happens to work because all
> metadata bits are above 32-bit. In theory, ZGC could store its metadata
> bits in the lower 32-bit part of the address, in which case this hash
> scheme would break. Today we have an ugly assert in
> JvmtiTagHashmap::hash() to make sure this doesn't happen. However, the
> JVMITagMap should not make assumptions on what an oop looks like, and
> should instead delegate this hashing to CollectedHeap.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8221732
> Webrev: http://cr.openjdk.java.net/~pliden/8221732/webrev.0
>
> /Per
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