Messages in this thread | | | Date | Wed, 05 Jan 2005 15:20:14 -0600 | From | "K.R. Foley" <> | Subject | Re: Real-Time Preemption, comparison to 2.6.10-mm1 |
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Mark_H_Johnson@Raytheon.com wrote: > K.R. Foley wrote: > >>Mark_H_Johnson@raytheon.com wrote: > > [snip - long explanation of how a nice application can starve a non > nice application for minutes at a time on an SMP system] > > >>>My point was that -mm definitely has the problem (though to a lesser >>>degree). The tests I ran showed it on both the disk read and disk copy >>>stress tests. I guess I should try a vanilla 2.6.10 run as well to see >>>if it is something introduced in the -mm series (it certainly is not a >>>recent change...). >> >>I'm curious if anyone is seeing this behavior on UP systems, or is it >>only happening on SMP? > > The build of 2.6.10 vanilla just completed and I reran my tests with > SMP and with MAXCPUS=1 (UP w/ SMP kernel).
Well that blows one of the theories I was looking at. :( -mm is carrying a patch that lengthens the cache_hot_time to roughly a ms instead of a usec, which could effect how fast tasks might be migrated to an idle cpu. > > The vanilla 2.6.10 kernel has the non RT starvation problem as well > for both test runs. It looks like this is not something in -mm but a > change between 2.4 and 2.6. > > I did notice the test results were a little inconsistent between the > two runs... > 2.6.10 SMP 2.6.10 UP (w/ SMP kernel) > disk write starved OK > disk copy OK starved > disk read starved starved > but in both cases, a non nice (non RT) disk application was > starved by a nice (non RT) cpu application for minutes.
Do you have a simple way of triggering and trapping the starvation? That of course is probably asking for a lot. :)
kr
> > I wonder who I should be talking to next (or submit a bug report?) > about this. > > --Mark > >
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