franz1981 edited a comment on issue #2832: ARTEMIS-2482 Large messages could leak native ByteBuffers URL: https://github.com/apache/activemq-artemis/pull/2832#issuecomment-530319911 @wy96f I've taken a second look to the way Netty handle thread local `ByteBuf`pools and I can confirm that `-Dio.netty.allocator.useCacheForAllThreads=false` should save non-netty threads from creating such thread local regions for tiny/small/medium sized buffers. While related to > but they just contain wrappers to direct memory that cannot be released (is part of the pool and they have no cleaner). The impact should be way less then IOUtil that pool native ByteBuffers holding exclusively native memory that won't be reused anymore... 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, but their size is quite small by default and the size I've chosen as `LARGE_MESSAGE_CHUNK_SIZE` (ie 100 * 1024) is `medium` but doesn't fall in any of those caches, so no real leak will happen until we allocate something smaller (could happen but is rare). IMO we should consider 2 separate improvements for a separate PR: - allow threads to stay alive forever and in a fixed number, but just idle (and maybe using the FJ thread pool executor instead of the AMQ thread pool executor in that case): in that case we can consider such caches to be ok to be used by *all* threads (including non-netty ones), because the leak is just to cope with future load - for the AMQ thread pool executor as it is, make the presence of such caches configurable and off by default wdyt? Thanks for the comment, good catch!
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