Re: 2.6.1 Scheduler Latency Measurements (Preemption diabled/enabled)

[Roger Larsson <roger.larsson@skelleftea.mail.telia.com>]

Christoph Stueckjuergen wrote:

>Hi,
>
>I performed a series of measurements comparing scheduler latency of a 2.6.1 
>kernel with preemption enabled and disabled on an AMD Elan (i486 compatible) 
>with 133 Mhz clock frequency.

OK, then you have worse hardware than I had when I started to measure
latency :-)

> - - - interesting way of trigger and measure deleted - - -

> The results are:
> "loaded" system, 10.000 samples
> average scheduler latency (preemption enabled / disabled): 170 us / 232 us
> minimum scheduler latency (preemption enabled / disabled): 49 us / 43 us
> maximum scheduler latency (preemption enabled / disabled): 840 us / 1063 us
> 
> "unloaded" system, 10.000 samples
> average scheduler latency (preemption enabled / disabled): 50 us / 44 us
> minimum scheduler latency (preemption enabled / disabled): 46 us / 41 us
> maximum scheduler latency (preemption enabled / disabled): 233 us / 215 us
> 

Robert Love said:
> That said, I would of expected slightly better numbers.

I would say that the numbers are quite good :-)
For comparation check
  http://www.gardena.net/benno/linux/audio/

There are some load tests there that you can use
to generate load: disk access, memory pressure, X11, ...

Note that more memory can result in worse latency, longer linked lists
to walk...

/RogerL

-- 
Roger Larsson
Skellefteå
Sweden