Messages in this thread | | | Date | Wed, 05 Jun 2002 11:05:12 -0700 | From | george anzinger <> | Subject | Re: realtime scheduling problems with 2.4 linux kernel >= 2.4.10 |
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Andi Kleen wrote: > > On Wed, Jun 05, 2002 at 01:53:06PM +0200, Ian Collinson wrote: > > > > > Are there any potentially negative consequences of this fix, apart from > > those already mentioned? > > I don't think so. > > It could still fail when you install a prio=99, SCHED_FIFO process. > > > I certainly vote for this feature being preserved, as it is extremely useful > > for debugging realtime priority apps. FYI, we narrowed it down to breaking > > in either 2.4.10-pre11 or pre12. > > That was when the low latency console changes went in. Before that console > switches could interrupt scheduling for a long time, causing problems > for other realtime people. The change was to move the expensive parts > of the console switch to keventd.
So that means that, with the above change to prio 99, we reintroduce the latency problem, only now it is in a task (keventd) and not an interrupt? (I know, I know, the work has to be done somewhere. At least this way we can control what priority level it is done at. I.e. this is a step in the right direction. I just what folks to be aware of the latency issue and where it is.)
For what its worth, you can change the priority of keventd AFTER a system is up. Robert Love's real time tools contain a program (rt I think) that will do this for you. Just follow the URL for preemption in my sig. file and look around.
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Real time sched: http://sourceforge.net/projects/rtsched/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml - 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/
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