Java’s new garbage collector promises low pause times on multi-terabyte heaps
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Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#2> Pointer colouring
(Is this the same as pointer tagging?)
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#3> Pointer colouring (Is this the same as pointer tagging?)
I would say that pointer colouring is a type of pointer tagging. AFAIK the colouring in ZGC represents different states. So the memory page mappings rely on the pointer having one colour (1 of the 4 bits set) whereas pointer tagging is the term for the general concept of encoding information in pointers.
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#4> GC’s SPECjbb 2015 throughput numbers are roughly comparable with the Parallel GC (which optimises for throughput) but with an average pause time of 1ms and a max of 4ms. This is in contrast to G1 and Parallel who had average pause times in excess of 200ms.
Not bad! Looking forward to seeing how this performs with a diverse range of workloads as it matures.
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#5Isn’t Java a pay-to-play runtime now? I thought Oracle changed the licensing model after Java 8?
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#6I'm glad they didn't buy into the refcount meme that's so inexplicably popular these days.
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#7The memory mapping trick they use on x86 to avoid masking only works up to the maximum 48 bits of addressable virtual memory, so there is much less than 22 free bits in that case.
It's also not quite free since it takes up TLB space.
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#8I'm glad they didn't buy into the refcount meme that's so inexplicably popular these days.
Could you elaborate? Why would refcount be a bad idea ? (genuine question)
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#9Isn’t Java a pay-to-play runtime now? I thought Oracle changed the licensing model after Java 8?
No it’s still free, they (Oracle) are just not supplying the free JVMs. There are plenty of alternatives for OpenJDK builds that are FOSS.
Re: Java’s new garbage collector promises low pause times on multi-terabyte heaps
#10Isn’t Java a pay-to-play runtime now? I thought Oracle changed the licensing model after Java 8?
No. The change was that you need to pay to get updates for older versions of the runtime.