RFR(S): 8068579: Running with -XX:-UseParallelGC does not turn ParalleGC off (original) (raw)
Per Liden per.liden at oracle.com
Tue Mar 15 13:48:16 UTC 2016
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Summary: Explicitly disabling the default collector, without specifying another collector, will silently re-enable the default collector. This is a bit counter intuitive. A better approach would be for the VM to complain about the situation.
Bug: https://bugs.openjdk.java.net/browse/JDK-8068579 Webrev: http://cr.openjdk.java.net/~pliden/8068579/webrev.0/ Testing: manual, jprt
Example (assuming it's a platform/configuration with G1 as default):
$ java -XX:-UseG1GC ...
Today, the above command will happily start a VM with G1 enabled.
With this patch the VM will instead complain, like this:
$ java -XX:-UseG1GC ... Error occurred during initialization of VM Garbage collector not selected (default collector explicitly disabled)
And of course, we're good with disabling the default collector as long as you specify some other collector, e.g.:
$ java -XX:-UseG1GC -XX:+UseParallelGC ...
cheers, Per
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