[jira] [Created] (SOLR-15562) Offer an MMapDirectoryFactory that writes with DirectIODirectory rather than FSDirectory.

["Mark Robert Miller (Jira)" <ji...@apache.org>]

Mark Robert Miller created SOLR-15562:
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             Summary: Offer an MMapDirectoryFactory that writes with DirectIODirectory rather than FSDirectory.
                 Key: SOLR-15562
                 URL: https://issues.apache.org/jira/browse/SOLR-15562
             Project: Solr
          Issue Type: Sub-task
      Security Level: Public (Default Security Level. Issues are Public)
            Reporter: Mark Robert Miller


DirectIODirectory uses a Java 10 feature to enable directio for merging so as to prevent merges from flooding the IO cache and replacing high value data with low value data.

MMapDirectory is the top read side Directory, you should allow using it with a better write side Directory.

Additionally, it might even be worth exploring how directio behaves in other read side spots.

Word on the street is that it can reduce kernel memory management resources and improve the poor unmap performance and that with a random read heavy load on SSDs, it *can* be a win, especially in combination with other available application caches.

Not wildly optimistic on the general read side, but perhaps worth taking a peak at.



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