Github user franz1981 commented on the issue:
https://github.com/apache/activemq-artemis/pull/1324
@michaelandrepearce
This PR aim to improve the performances (and memory footprint too) while
performing reads while Paging when NIO (not JDBC) Paging is in charge.
In addition, the proposal of @clebertsuconic is to use this enhancement as
a feature of all the SequentialFile implementations that could support it,
similar to what I've done in this branch:
https://github.com/franz1981/activemq-artemis/tree/mapped_view_seq_file.
The reason is to speed up the load phase of the journal, but as I've
pointed out (and you too), with AIO is needed some additional tests to be sure
it's worth.
Right now I'll prefer to stick to support it only with Paging.
Just thinking loud...
A different case would be if we start to use the Journal to be read (LMDB
do that and AFAIK Kafka too) and using a map (a BloomFilter would be better) to
store where the the records are stored in the journal.
In that case having AIO and exploiting the OS Page Cache could be a very
nice idea to avoid the cache to be filled of new OS pages that doesn't have the
locality required by the read load patterns.
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