low(er) disk performance with sched_4bsd then with sched_ule
gallatin at cs.duke.edu
Mon Sep 19 11:06:27 PDT 2005
Scott Long writes:
> I don't know if it's the case here or not, but GCC now does very
> aggressive function inlining, so much so that it's nearly impossible
> to look at a backtrace and figure out what the actual call path was.
> Compiling with -O instead of the -O2 default turns off this 'feature'
> (and I use that term quite liberally), so it might be useful to
> recompile there kernel with 'CFLAGS= -O' in /etc/make.conf and see
> if it changes the profiling numbers at all.
If inlining were at fault, I would expect to see something which
calls bcopy (copin/copyout or uiomove) have a lot of samples.
> Also, I think that there was some talk last year about things like
> preemption and fast interrupts screwing up certain kinds of profiling.
> I don't recall if there was a solution to this, though.
I wonder if this could be it. But I'm still not sure how they
could interfere with a copyin/copyout in a process context..
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