Promptly freeing the per-thread cached direct buffers when a thread exits

Peter Levart peter.levart at
Mon Apr 9 10:21:24 UTC 2018

On 04/09/18 10:33, David Holmes wrote:
>> After thread exits, ThreadLocal values associated with it are no 
>> longer reachable from its Thread object.
>> The problem Tony faces is that by the time this happens, direct 
>> ByteBuffer's that were cached using such ThreadLocal value, are 
>> already moved to old GC generation, waiting for full GC to release 
>> them together with direct memory they are holding.
> Right. So the suggestion was to call ThreadLocal.remove() instead (as 
> well as?) so that you could define a custom ThreadLocal class for the 
> buffers that override remove() to actually release the buffer directly.
> David 

Ah, of course. But the concern is that custom code at thread-exit is not 
desirable. Alan is propagating private internal API. Here's a prototype:

Would something like this be acceptable?

Regards, Peter

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