On Thu, 20 Jul 2023 10:26:03 GMT, Doug Lea <d...@openjdk.org> wrote:
>> This update addresses performance issues across both LinkedTransferQueue and
>> SynchronousQueue by creating a common basis for implementation across them
>> (mainly in LinkedTransferQueue). Pasting from internal doc summary of
>> changes:
>> * * Class DualNode replaces Qnode, with fields and methods
>> * that apply to any match-based dual data structure, and now
>> * usable in other j.u.c classes. in particular, SynchronousQueue.
>> * * Blocking control (in class DualNode) accommodates
>> * VirtualThreads and (perhaps virtualized) uniprocessors.
>> * * All fields of this class (LinkedTransferQueue) are
>> * default-initializable (to null), allowing further extension
>> * (in particular, SynchronousQueue.Transferer)
>> * * Head and tail fields are lazily initialized rather than set
>> * to a dummy node, while also reducing retries under heavy
>> * contention and misorderings, and relaxing some accesses,
>> * requiring accommodation in many places (as well as
>> * adjustments in WhiteBox tests).
>
> Doug Lea has updated the pull request incrementally with one additional
> commit since the last revision:
>
> nitpicks
A backport note: This set of changes may be applied jdk19+ by removing only the
lines (currently L423-424) in LinkedTransferQueue:
if w.isVirtual()) // don't spin
spin = false;
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PR Comment: https://git.openjdk.org/jdk/pull/14317#issuecomment-1643696658
