RFR: 8210064: ZGC: Introduce ZConcurrentRootsIterator for scanning a subset of strong IN_NATIVE roots concurrently
Per Liden
per.liden at oracle.com
Fri Aug 31 07:57:44 UTC 2018
Hi Erik,
On 08/30/2018 10:46 AM, Erik Österlund wrote:
> Hi,
>
> We now have enough load barriers to support scanning of CLDs and JNI
> handles concurrently. I propose to do that and move these root sets out
> from ZRootsIterator, and hence the GC pause. They will be scanned during
> concurrent marking (and heap iteration), but no longer during relocation.
>
> I still perform ClassLoaderDataGraph::clear_claimed_marks() in the pause
> because it seems cheap. But it can be moved out of the pause when Coleen
> gets her new cool CLDG lock in.
>
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8210064/webrev.00/
I have some minor requests. Instead of listing them all, I attached a
patch which addresses those.
The main thing is that I don't think ZDriver should know about
"concurrent roots", just that it's doing "mark" or "mark continue", so I
suggest we turn that into a "bool initial" argument to mark() instead of
exposing a mark_concurrent_roots() function.
The other things are minor style adjustments.
/Per
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8210064
>
> Tested through hs-tier1-3.
>
> Thanks,
> /Erik
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