RFR: JDK-8212186: JVMTI lacks a few GC barriers/hooks
per.liden at oracle.com
Thu Oct 18 07:13:44 UTC 2018
On 10/17/2018 07:10 PM, Roman Kennke wrote:
>> Hi Roman,
>> Looks fantastic.
>> BTW, out of curiosity, how do you do the heap walk - scanning or tracing?
> Tracing. Scanning would require to carry around complete marking info
> (to be able to avoid holes of dead objects with recycled Klass*), which
> we don't.
So that makes me wonder why you needed JDK-8211955 (GC abstraction for
LAB reserve) and why you insert filler objects at all? Am I missing
>>> On 17 Oct 2018, at 11:48, Roman Kennke <rkennke at redhat.com> wrote:
>>> Erik recently pointed out that JvmtiTagHashmapEntry::equals() is
>>> lacking on obj-equals-barrier, and that JvmtiTagHashmap::hash() better
>>> does ::resolve() the object to a stable value before casting it to a raw
>>> This lead us to do some more JVMTI testing and we found that we have a
>>> little inconsistency with reporting object size too: the VMObjectAlloc
>>> callback now reports a different size that GetObjectSize(). This is also
>>> fixed by this proposed change:
>>> Testing: hotspot/tier1, nsk/jvmti with Shenandoah
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