Re: PREEMPT_RT vs I-PIPE: the numbers, part 2

[Karim Yaghmour <karim@opersys.com>]

Ingo Molnar wrote:
> the UDP-over-localhost latency was a softirq processing bug that is 
> fixed in current PREEMPT_RT patches. (real over-the-network latency was 
> never impacted, that's why it wasnt noticed before.)

That's good to hear, but here are some random stats from the
idle run:

Measurements   |   Vanilla   |  preemp_rt     |   ipipe
---------------+-------------+----------------+-------------
fork           |      95us   |  157us (+65%)  |   97us (+2%)
open/close     |     1.4us   |  2.1us (+50%)  |  1.4us (~)
execve         |     355us   |  452us (+27%)  |  365us (+3%)
select 500fd   |    12.7us   | 27.7us (+118%) | 12.7us (~)
mmap           |     660us   | 2886us (+337%) |  673us (+2%)
...            |      ...    |   ...          |   ...

Here's a under ping flood conditions:

Measurements   |   Vanilla   |  preemp_rt     |   ipipe
---------------+-------------+----------------+-------------
fork           |     112us   |  223us (+99%)  |  121us (+8%)
open/close     |     1.7us   |  3.0us (+76%)  |  1.8us (+6%)
execve         |     421us   |  652us (+55%)  |  467us (+11%)
select 500fd   |    14.6us   | 38.1us (+161%) | 15.5us (+6%)
mmap           |     760us   | 3936us (+418%) |  819us (+8%)
...            |      ...    |   ...          |   ...

etc. it's like this accross the board.

Unless that fix you mention above takes care of these, there's
something seriously wrong going on here.

Are there existing LMbench results posted of PREEMPT_RT which
one can go back to for comparison?

Karim
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