franz1981 commented on issue #2522: ARTEMIS-2239 Zero-copy NIO/MAPPED TimedBuffer URL: https://github.com/apache/activemq-artemis/pull/2522#issuecomment-460938230 @michaelandrepearce @clebertsuconic I've manged to obtain the CPU flamgegraphs of the time spent on `TimedBuffer::flushBatch` and I see that the changes of this PR save a visible amount of CPU dependent by the accumulated written bytes into `TimedBuffer`. This is the flames of `master`:  While with this PR:  The violet part represent the CPU cycles spent zeroing the buffer and it's ~20% of the total time spent on `TimedBuffer::flushBuffer`. As a note: I've mentioned that a further (important) improvement on NIO/MAPPED would be to allow `fdatasync` and the callbacks to be called on an external thread (dedicated, like ASYNCIO on blockedPoll) and it's correct: with a very fast disk `fdatasync` is not that costy, but waking up threads while executing `OperationContextImpl::done` is one of the dominant costs (the 2 bars on the left).
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