Messages in this thread | | | Subject | Re: [RFC][PATCH -rt] sched: fully ignore RT tasks for CFS load-balancing | From | Peter Zijlstra <> | Date | Wed, 26 Aug 2009 21:04:45 +0200 |
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On Wed, 2009-08-26 at 11:52 -0700, Darren Hart wrote: > Peter Zijlstra wrote: > > Since -rt runs IRQs and SoftIRQs as RT tasks and load-balancing is done > > from softirq context, there is always at least one RT task (and very > > likely multiple) running when we balance. > > > > The current (and totally broken) interaction between RT tasks and CFS > > load-balancing makes it so that we'll try to evacuate a significant > > amount of tasks due to RT tasks being runnable. > > > > Solve this in another broken way by not accounting RT tasks at all. > > > > This will likely break another class of cases, but until we can properly > > fix this, we might as well do this. > > Peter, > > Do we know why this became a problem lately? I don't recall seeing load > balancing issues like this way back around 2.6.21 or 22 when CFS was > released. Is the cpu_load stuff fairly recent?
The earlier problem solved by the previous patch was caused by tglx tinkering with the cpu_load computation.
This particular problem I'm not sure about, afaict it should have been present a long long time.
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