Messages in this thread | | | Date | Thu, 4 Nov 2004 16:16:31 +0100 | From | Ingo Molnar <> | Subject | Re: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm2-V0.7.1 |
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* Mark_H_Johnson@raytheon.com <Mark_H_Johnson@raytheon.com> wrote:
> Let me follow up briefly on the regression I noticed yesterday on ping > responses from an SMP system with one real time task running. [...]
icmp/ping replies are handled by ksoftirqd. Once a networking request has been handed to ksoftirqd it cannot be redirected to another CPU, because softirq processing is fundamentally per-CPU. So if the network interrupt hits the CPU where the RT-task is running then the RT task will starve that ksoftirq instance (and hence the reply) even if another CPU in the system is idle.
i agree that this is an SMP/RT artifact that should be fixed. hardirq workload can be redirected to other CPUs because it's single-threaded, but it's not that easy for softirq workload.
i suspect the same phenomenon causes some of the other scheduling artifacts ('frozen' X) you've noticed.
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