Details
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Enhancement
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Status: Resolved
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P4
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Resolution: Fixed
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8-shenandoah, 11.0.9, 16, 17
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b10
Description
Shenandoah currently uses its own marking bitmap (added by JDK-8254315). It accesses the marking bitmap with "acquire" for reads and "conservative" for updates. Hotspot's default for atomic operations is memory_order_conservative, which emits two-way memory fences around the CASes at least on AArch64 and PPC64.
I think both are actually excessive for marking bitmap accesses: we do not piggyback object updates on it, the atomics there are only to guarantee the access atomicity and CAS updates to bits. It seems "relaxed" is enough for marking bitmap accesses.
I think both are actually excessive for marking bitmap accesses: we do not piggyback object updates on it, the atomics there are only to guarantee the access atomicity and CAS updates to bits. It seems "relaxed" is enough for marking bitmap accesses.
Attachments
Issue Links
- is blocked by
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JDK-8254315 Shenandoah: Concurrent weak reference processing
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- Resolved
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