Messages in this thread | | | Date | Thu, 29 Nov 2007 12:50:11 +0100 | From | Ingo Molnar <> | Subject | Re: scheduling anomaly on uml (was: -rt doesn't compile for UML) |
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* Miklos Szeredi <miklos@szeredi.hu> wrote:
> > how come UML idled for 30 msecs here, while the workload was > > supposed to be CPU-bound? It's not IO bound anywhere, right? No SMP > > artifacts either, right? > > Yes. The UML kernel is UP, and I don't think 'date' or 'bash' want to > do any disk I/O. > > Could disk I/O be blocking the tty? I think UML uses separate threads > for these, but I don't know the details.
even if the workload is fully CPU bound externally - internally a request to the external (CPU-bound) thread will look like an asynchonous request - so small amounts of idle time can be within UML, legitimately. (for the amount of time it takes for the external thread to service the request)
30 msecs already sounds a bit excessive (this is on your T60 with Core2Duo, right?), and 1-2 seconds noticeable latency is definitely excessive.
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