[GitHub] [activemq-artemis] wy96f commented on issue #2832: ARTEMIS-2482 Large messages could leak native ByteBuffers

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wy96f commented on issue #2832: ARTEMIS-2482 Large messages could leak native 
ByteBuffers
URL: https://github.com/apache/activemq-artemis/pull/2832#issuecomment-531654209
 
 
   @franz1981 
   
   > I have to add more detail and I was wrong: the tiny/small/medium thread 
local caches are actually leaking memory regions (with default 
io.netty.allocator.useCacheForAllThread) that need the holding thread to die in 
order to make them available to other threads again
   
   I assumed memory released into tiny/small/medium cache would be leaked if 
holding thread terminates until I looked at the code in PoolThreadCache:
   ```
   /// TODO: In the future when we move to Java9+ we should use 
java.lang.ref.Cleaner.
       @Override
       protected void finalize() throws Throwable {
           try {
               super.finalize();
           } finally {
               free();
           }
       }
   
       /**
        *  Should be called if the Thread that uses this cache is about to 
exist to release resources out of the cache
        */
       void free() {
           // As free() may be called either by the finalizer or by 
FastThreadLocal.onRemoval(...) we need to ensure
           // we only call this one time.
           if (freed.compareAndSet(false, true)) {
               int numFreed = free(tinySubPageDirectCaches) +
                       free(smallSubPageDirectCaches) +
                       free(normalDirectCaches) +
                       free(tinySubPageHeapCaches) +
                       free(smallSubPageHeapCaches) +
                       free(normalHeapCaches);
   
               if (numFreed > 0 && logger.isDebugEnabled()) {
                   logger.debug("Freed {} thread-local buffer(s) from thread: 
{}", numFreed,
                           Thread.currentThread().getName());
               }
   
               if (directArena != null) {
                   directArena.numThreadCaches.getAndDecrement();
               }
   
               if (heapArena != null) {
                   heapArena.numThreadCaches.getAndDecrement();
               }
           }
       }
   ```
   So the cache will be freed and used by other threads when thread dies? If 
so, it seems no any leak problems with this pr, no need with improvements?

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