thread priority mapping to jstack prio

[Kevin Burton]

Can't find any documentation on this so I figured I'd post here.

I have a thread which should be in MIN_PRIORITY (1) .. and if I execute it, and read back the priority, it's correct.

However, when I run 'jstack' on the JVM I get back prio=5 which is NORM_PRIORITY...

In production, they're all being set to prio=10.. which is even weirder.  

I haven't had a problem with this before so I'm really confused as to what's happening.

[Kevin Burton]

ouch.. looks like it's just wrong on Linux!

http://mail.openjdk.java.net/pipermail/hotspot-dev/2012-September/006431.html

[Peter Booth]

Remember there's another factor to consider here: Thread.setPriority() doesn't do anything in Linux for the common case.

It only has an effect if you use the switch
-XX:ThreadPriorityPolicy and run as root. It's funny how much Java code I see that valiantly attempts to define thread priorities without using these.

Peter

[Jan Kotek]

Perhaps there is workaround to change priority of single thread (not entire JVM) from command-line.

Jan