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SubjectRe: Poor UDP performance using 2.6.21-rc5-rt5
Date
Thanks for all the input Ingo, Here's a list of all the permutations I've tried:

setup Thruput CPU% from cyclesoak
2.6.21-rc5 vanilla 935 29%

2.6.21-rc5-rt5 711 50% //basically all of 1 cpu

2.6.21-rc5-rt8 733 52%

2.6.21-rc5-rt8 824 64%
netperf @50
hardirq @50
softirq @50

2.6.21-rc5-rt8 937 74%
netperf @51
hardirq @50
softirq @50

2.6.21-rc5-rt8 106 8%
netperf @51
hardirq @49
softirq @50

2.6.21-rc5-rt8 233 14%
netperf @51
hardirq @49
softirq @48

2.6.21-rc5-rt8 67 5%
netperf @batch
hardirq @batch
softirq @batch

2.6.21-rc5-rt8 331 OFF
netperf @batch
hardirq @batch
softirq @batch
cyclesoak off


Any thoughts?

-Dave



-------------- Original message ----------------------
From: Ingo Molnar <mingo@elte.hu>
>
> * Dave Sperry <dave_sperry@ieee.org> wrote:
>
> > I checked the clock source and in both the vanilla and rt cases and
> > they were both acpi_pm
>
> ok, thanks for double-checking that.
>
> > Here's the oprofile for my vanilla case:
>
> i tried your workload and i think i managed to optimize it some more: i
> have uploaded the -rt8 kernel with these improvements included - could
> you try it? Is there any measurable improvement relative to -rt5?
>
> one more thing to improve netperf performance is to do this before
> running it:
>
> chrt -f -p 50 $$
>
> this will put netperf on the same priority level as the net hardirq and
> the net softirq (which both default to SCHED_FIFO:50), and should result
> in a (much) reduced context-switch rate.
>
> Or, if networking is not latency-critical, then you could move the net
> hardirq and softirq threads to SCHED_BATCH, and run netperf under
> SCHED_BATCH as well, using:
>
> chrt -b -p 0 $$
>
> and figuring out the active softirq hardirq thread PIDs and "chrt -b"
> -ing them too.
>
> Ingo

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