Parallel GC and array object layout: way off the base and laid out in reverse?

Igor Veresov igor.veresov at
Tue Sep 17 11:42:10 PDT 2013

Yup, that's ok.


On Sep 17, 2013, at 4:17 AM, Aleksey Shipilev <aleksey.shipilev at> wrote:

> On 09/07/2013 11:27 AM, Tony Printezis wrote:
>> Igor made all the points I wanted to make. :-) Looking forward to the
>> performance comparisons. I'm actually curious to see how things will
>> look with the backwards array scanning.
> Ok, here is the current fix:
> I haven't tested the performance on large scale yet, because wanted to
> cross-check if this is a viable solution code-wise.
> It reliably fixes the layout problems on my test with
> -XX:ParallelGCThreads=1. With more than one GC thread I still
> occasionally get the reverse order. My hypothesis is that while original
> GC worker can process the array in forward order, *stealing* that work
> by some other worker will do the effective reverse.
> -Aleksey.

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