Messages in this thread | | | Date | Thu, 25 Nov 2004 18:14:30 +0100 | From | Ingo Molnar <> | Subject | Re: Priority Inheritance Test (Real-Time Preemption) |
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* Esben Nielsen <simlo@phys.au.dk> wrote:
> > On Thu, 25 Nov 2004, Ingo Molnar wrote: > > > [...] > > there's one thing i noticed, now that the blocker device is in the > > kernel, you have to be really careful to compile the userspace loop() > > code via the same gcc flags as the kernel did. Minor differences in > > compiler options can skew the timing calibration. > > > > but any such bug should at most cause a linear deviation via a constant > > factor multiplication, while the data shows a systematic nonlinear > > transformation. > > > -g -Wall -O2 was on in userspace.
you can check the gcc options the kernel used via the drivers/char/.blocker.o.cmd file. Mine has (only the performance-relevant flags):
-fno-strict-aliasing -fno-common -O2 -fomit-frame-pointer -msoft-float -mpreferred-stack-boundary=2 -fno-unit-at-a-time -march=pentium3 -mregparm=3
> > [...] > > yeah, i agree that this has to be further investigated. What type of box > > did you test it on - UP or SMP? (SMP scheduling of RT tasks only got > > fully correct in the very latest -31-7 kernel.) > > > UP, PIII 697.143 Mhz
ok - some of the fixes affect UP too, but with less likelyhood. Might be worth a try though.
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