Messages in this thread | | | Date | Thu, 28 Aug 2008 13:09:23 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH 6/6] sched: disabled rt-bandwidth by default |
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> Even if the system has multiple CPUs, and even if just a single CPU is > fully utilized by an RT task, without the rt-limit the system will still > lock up in practice due to various other factors: workqueues and tasks > being 'stuck' on CPUs that host an RT hog.
The load balancer will not notice that a particular CPU is busy with real time tasks?
> While there's obviously CPU > time available on other CPUs, you cannot run 'top', the desktop will > freeze, work flows of the system can be stuck, etc, etc..
I had such a situation at least once in the past (not due run away RT but due a kernel bug) and even with 2 out of 4 CPUs blocked the system was still quite usable. top/kill definitely worked. The system didn't have a desktop, but I didn't notice many problems in shell use. Ok it's just one sample.
That said I don't think having such a limit by default is a bad idea actually.
Just handling it in the scheduler anyways is also probably good because it can happen even due to other issues than just run away RT tasks.
-Andi
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