Messages in this thread | | | From | "David Schwartz" <> | Subject | RE: Two questions about scheduling and threading. | Date | Thu, 8 May 2008 12:44:17 -0700 |
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> When I start my system for the first time, I start one thread for each > processor/core in the machine (is this the correct thing to do)? These > threads set a busy flag, go to work and then go to sleep. I put > everything > to sleep as opposed to killing the threads because it saves me on > average of > about 400ms each time around.
That's not unreasonable. However, you may wish to create a few extra threads. Otherwise, if one thread is blocked on I/O, you can't use all the CPUs.
> My problem is, and, it is very reproducable, that if CPU0 is at 100%, none > of my threads see the wakeup! It doesn't matter what the other CPU's are > doing, if they're all at 0 or 100%, but if CPU0 is 100, I'm > toast. Is there > anyway around this?
Sounds like a bug. What does your wakeup code look like? Do you put your threads to sleep blocked on a condition variable? Is the c.v. code correctly using a predicate, that's something easy to screw up. It's like 'select', there's a dozen classic mistakes and someone often makes one or two of them and their code still soemtimes works.
> Also, I know that we're supposed to sit back and let the scheduler do all > the work for us; but, in the 2.6.16.16 kernel, is there a way to assign a > specific thread and/or process to a designated processor??? I really need > to be able to do this because even with the preemptive > scheduling, I'm still > real-time and it's not quite real-time enough!
Big mistake. If you bind threads to CPUs and the thread that gets a wakeup is assigned to a CPU that's busy, the job that thread was going to do will have to wait, while other CPUs sit idle.
DS
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