06/24/2008 6:26 PM
thread scheduling jitter question
I have 3 processes each running a number of threads. I have some of the threads running at a higher priority and system
scope. some of the threads (including those running at higher priorities) are communicating over ethernet. I have an
SMP x86 box with two gigabit ethernet ports. I am running the round robin scheduler.
I am using timers to block the thread to run at 250, 500, etc. milliseconds. I expected to see the intervals be very
close to the proscribed value. That is, I expected to see numbers close to 250 milliseconds, etc. but instead I see a
significant amount of jitter. In some cases a couple of hundred milliseconds, normally though about 5 milliseconds plus
/minus the timeout value.
One thread I have raised to 255 to see if that made any difference. It still has a great deal of jitter. I am very
Is this normal for QNX or am I doing something wrong?