On Fri, Oct 05, 2007 at 07:15:48PM -0700, Mike Kravetz wrote: > After applying the fix to try_to_wake_up() I was still seeing some large > latencies for realtime tasks.
I've been looking for places in the code where reschedule IPIs should be sent in the case of 'overload' to redistribute RealTime tasks based on priority. However, an even more basic question to ask might be: Are the use of reschedule IPIs reliable enough for this purpose. In the code, there is the following comment: /* * this function sends a 'reschedule' IPI to another CPU. * it goes straight through and wastes no time serializing * anything. Worst case is that we lose a reschedule ... */ After a quick read of the code, it does appear that reschedule's can be lost if the the IPI is sent at just the right time in schedule processing. Can someone confirm this is actually the case? The issue I see is that the 'rt_overload' mechanism depends on reschedule IPIs for RealTime scheduling semantics. If this is not a reliable mechanism then this can lead to breakdowns in RealTime scheduling semantics. Are these accurate statements? I'll start working on a reliable delivery mechanism for RealTime scheduling. But, I just want to make sure that is really necessary. -- Mike - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
