RFR (round 1), JDK-8214259: Implementation: JEP 189: Shenandoah: A Low-Pause Garbage Collector

Roman Kennke rkennke at redhat.com
Wed Nov 28 14:00:21 UTC 2018


Hi Per,

> Hi Roman,
> 
> On 11/26/18 10:39 PM, Roman Kennke wrote:
> [...]
>>   *) shared-serviceability
>> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shared-serviceability/>
>>
>>      - The usual code to support another GC
> 
> Just had a quick look at the SA part. I was thinking you'd have the same
> problem as ZGC here, with regards to parsing the heap and potentially
> reading garbage when you step on a Klass* which had been unloaded?

Possible. I am myself not very familiar with SA. I guess it depends on
how SA does it: if it iterates objects via CH::object_iterate() (e.g.
same entry point as, e.g., heap-dumping code), then we should be fine.
We're kicking off a traversal rather than straight scan there. If
however SA somehow makes a raw scan itself, then we'd have the problem
you describe.

Roman




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