Enabling use of hugepages with java
rachmato at redhat.com
Wed Feb 28 15:20:22 UTC 2018
I hope that I am directing this question to the correct mailing list.
I have a question concerning the OS setup on Linux required for correct
use of the java option -XX:+UseLargePages in JDK 8.
Official Oracle documentation
suggests that in order to make use of large memory pages, in addition to
setting the flag -XX:+UseLargePages, an OS option shmmax needs to be
tuned to be larger than the java heap size.
From looking at the java documentation, there are various ways of
enabling the use of huge pages: -XX:+UseHugeTLBFS,
-XX:+UseTransparentHugePages, -XX:+UseSHM and, if I understand
correctly, these correspond in part to making use of different OS-level
APIs for accessing huge pages (via shared memory, hugetlbfs, and other
My question is this: is setting the shmmax OS value only relevant if we
are using -XX:+UseSHM? In other words, if we are using -XX:+UseHugeTLBFS
to enable use of hugepages by the JVM, is it the case that setting the
shmmax OS setting has no effect on the use of hugepages by the JVM?
Thanks in advance
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