Re: [patch] voluntary-preempt-2.6.8.1-P0

Lee Revell
2004-08-15T23:50:38Z

On Sun, 2004-08-15 at 07:56, Ingo Molnar wrote:
> i've uploaded the -P0 patch:
>
> http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.8.1-P0
>
> those who had APIC (and USB, under SMP) problems under previous
> versions, are the problems still present in -P0?
>

The mlockall issue is still not resolved; however, I did manage to get a
trace, which was probably not possible before because some higher
latency but lower frequency event was overwriting /proc/latency_trace.
So, maybe mlockall does cause xruns by having many shorter, but long
enough to be problematic, non-preemptible sections.

http://krustophenia.net/testresults.php?dataset=2.6.8.1-P0

Also it seems that extract_entropy still causes high latencies, even
though a call to preempt_schedule was added. I looked at the code in
random.c a bit and this strikes me as an area where the algorithm could
be improved, rather than adding a scheduling point. Do we really need
*that* much entropy, right then? And if so, isn't there a zero-copy
solution?

Lee