I wanted to get some clarification about the 4BSD scheduler. I am sort of confused why there are two forms of scheduling, one done between processes and another done between threads in a process. The priority calculations seem to be done only with processes and I assume that the global run queue holds processes, not threads. Also why is there only 1 run queue for 1 CPU. What happens to blocked processes and ready to be runned processes?
Part of the challenge of adding threads to a system is to make it hard for a threaded process to "flood" the system run queues so that other processes
get no cpu time.
The scheme in the current freeBSD schedulers is a "crude" method, by which
only a limitted number of threads per process are allowed to be added to
the system run queue. RUnnable hreads fo r aprocess are kept on a run queue for the process and only the highest N prioriy hreads are actually put on the
system run queue.
This is by no means the best way, but rather the easiest way. I am hoping that some PhD candidate somewhere will decide that thread scheduling is his topic and will figure out a better way of doing this.
both run queues hold threads. This is still a place wjere a lot of work can be done.
:-)
Ash _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
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