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https://issues.apache.org/jira/browse/HBASE-23794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17030018#comment-17030018
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Mark Robert Miller commented on HBASE-23794:
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I'm still working out what a good suggestion for a value might be. Very few of
the tests need even more than 1g of the 2g of heap given, so I'm looking into
some numbers between the two things.
Largely, it is just nice to be explicit so that all devs and CI envs get the
same value. Older hotspot might default to lower explicit values depending on
arch/client/server, more recent hotspot defaults to Xmx, hotspot can change
again, other JVM's could do whatever. So a lot of the improvement I imagine
here is just consistency of the build and knowing the value has been set high
enough for the tests.
I've run into fails due to this while playing around with giving tests less
resources - so I'd like to set it high enough to avoid any fails, but also
remove this confusion around messing with Xmx and running into off heap
allocation failures and that type of thing.
> Consider setting -XX:MaxDirectMemorySize in the root Maven pom.xml file.
> ------------------------------------------------------------------------
>
> Key: HBASE-23794
> URL: https://issues.apache.org/jira/browse/HBASE-23794
> Project: HBase
> Issue Type: Test
> Reporter: Mark Robert Miller
> Priority: Minor
>
> -XX:MaxDirectMemorySize is an artificial governor on how much off heap memory
> can be allocated.
> It would be nice to specify explicitly because:
> # The default can vary by platform / jvm impl - some devs may see random
> fails
> # It's just a limiter, it won't pre allocate or anything
> # A test env should normally ensure a healthy limit as would be done in
> production
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