Hugepages and Java

As a data point, at a previous employer we played a little with the use of HugePages and memory mapped files in an attempt to get better performance.
Java’s support for the use of HugePages is on a best effort basis and our experimentation found that java was initially using the HugePages, but over time (a few hours), the HugePages were no longer used by the JVM—thus effectively reducing the available amount of RAM by the amount allocated for HugePages. We ended up disabling HugePages for our usage. I do not recall any concern/investigation about the Anonymous huge pages.
 
In the above case, however, we were constantly changing the memmapped files (these were large image files), since each request would access different image files, and the files were accessed over network storage.
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Filed under JVM, Linux

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