The Fair Share Scheduler was introduced in Solaris 9 but if it is used to run a JVM with thread priorities enabled, the JVM's attempts to manage thread priorities fail. This is because the JVM uses low-level scheduler interfaces (priocntl(2)) without catering for FSS.

----------
$ priocntl -e -c TS java -XX:+UnlockDiagnosticVMOptions -XX:+UseThreadPriorities -XX:+ThreadPriorityVerbose -version

lwp_priocntl_init: Class=1(TS)...
Thread priority Range: [-60..0]

In create_os_thread, Thread 0x0000000000000002, LWP is 0x0000000000000002

In create_thread, creating a pgc thread

In create_thread, creating a pgc thread

Starting Thread 0x0000000000000003, LWP is 0x0000000000000003, setting priority: 5

set_lwp_class_and_priority(0x0000000000000003@0x0000000000000003 5)
TS: [-60...5] 5->-58
----------

----------
priocntl -e -c FSS java -XX:+UnlockDiagnosticVMOptions -XX:+UseThreadPriorities -XX:+ThreadPriorityVerbose -version
lwp_priocntl_init: Class=3(FSS)...
Unknown scheduling class: FSS ...

In create_os_thread, Thread 0x0000000000000002, LWP is 0x0000000000000002

In create_thread, creating a pgc thread

In create_thread, creating a pgc thread

Starting Thread 0x0000000000000003, LWP is 0x0000000000000003, setting priority: 5

Trying to set priority but init failed, ignoring
Starting Thread 0x0000000000000004, LWP is 0x0000000000000004, setting priority: 5

Trying to set priority but init failed, ignoring
In create_thread, creating a pgc thread
----------