[master] RFR: Unconditionally preserve all marks during GC
rkennke at openjdk.java.net
Tue May 18 21:01:29 UTC 2021
When storing the Klass* in the object header, we need to preserve all marks during GC, because otherwise we'd be loosing the Klass*.
This means that the PreservedMarks structure is repurposed as a full (reverse) forwarding table. Reverse because instead of mapping object->forwardee, and leaving the mark alone, it maps object->mark and stores the forwardee in the header, which might be a better idea because it means we can have a most compact table.
Shenandoah doesn't have this problem, except during full-GC, and ZGC has its own forwarding table.
This change will likely affect performance, but I haven't checked by how much, yet. It's probably more useful to see this in the context of actually reduced header.
- [x] tier1
- [ ] tier2
- Unconditionally preserve all marks during GC
Stats: 117 lines in 15 files changed: 0 ins; 106 del; 11 mod
Fetch: git fetch https://git.openjdk.java.net/lilliput pull/6/head:pull/6
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