Messages in this thread | | | Date | Fri, 25 Feb 2005 05:25:18 +0100 | From | Mike Galbraith <> | Subject | Re: Xterm Hangs - Possible scheduler defect? |
| |
At 12:53 PM 2/24/2005 -0500, Chad N. Tindel wrote: > > > Hmmm... Are you suggesting it is OK for a kernel to get nearly completely > > > hosed and for not fully utilize all the processors in the system because > > > of one SCHED_FIFO thread? > > > > Sure. You specifically directed the scheduler to run your thread at a > > higher priority than anything else. The way I see it, you used root's > > perogative to shoot himself in the foot. You could also have used root's > > perogative to don steel toed shoes(set important kernel threads to a higher > > priority) before pulling the trigger. > >No, I specifically directed the scheduler to run my thread at a higher >priority than any other userspace application. The fact that I wrote it >in userspace and not in kernel space implies that I am OK with the kernel >stopping me sometimes when _it_ has work to do. If I wanted something >higher priority than the kernel I would have written something in kernel >space instead.
Nope. You may have _thought_ you told it that, but the reality is as I described it.
> > SCHED_FIFO thread are supposed to preempt > > > all other userspace threads... not the kernel itself. > > > > Not so. The scheduler makes do distinction between user and kernel threads > > of execution. > >That is SOOOO broken it isn't even funny.
I heartily disagree. I call it flexible/powerful.
> > If you think that's broken, you'll _love_ Ingo's IRQ threads... > >Yeah, thats broken too.
(You're not noticing the added power it gives you.)
>Perhaps I don't understand this philosophy you have where the kernel >isn't more important than everything else. It seems to me like there needs >to be a rigid hierarchy for scheduling, lest you get into deadlock problems:
Some kernel thread flushing buffers should be more important than my userland trigger-pacemaker thread?
>Under no circumstances should any single CPU-bound userspace thread >completely >hose a 64-way SMP box.
I can certainly agree that any service which is required across processor borders wants to be very high priority indeed, and I can further agree that this crossing of borders would not exist in a perfect world.
-Mike
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |