Nate McCall created CASSANDRA-10702:
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Summary: Statement concerning default ParallelGCThreads in
jvm.options is not correct
Key: CASSANDRA-10702
URL: https://issues.apache.org/jira/browse/CASSANDRA-10702
Project: Cassandra
Issue Type: Bug
Components: Configuration
Reporter: Nate McCall
Priority: Trivial
from {{jvm.options}}:
bq. The JVM maximum is 8 PGC threads and 1/4 of that for ConcGC.
This is not correct. If there are more than eight CPUs, the default becomes 5/8
of the number of CPUs rounded up to the nearest even number (it seems - see
below). See {{-XX:ParallelGCThreads=n}} secion of
http://www.oracle.com/technetwork/articles/java/g1gc-1984535.html
Pretty easy to test with > 16 cores (as 5/8 of such is 10): turn on GC logging,
leave the defaults, and the G1GC output will show something like:
{noformat}
[Parallel Time: 342.6 ms, GC Workers: 16]
{noformat}
on a 24 core system in this case.
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