[TEST/REVIEW] cpu time accounting patch, step 2

[Robert Watson]

On Fri, 10 Feb 2006, Andrew Gallatin wrote:

> Unfortunately, even after your patch, we are still about 38% slower than 
> linux x86_64 on the same box for loopback ping-pong, and 32% slower for 
> ping-pong over 10GbE.  (bandwidth is lower for streaming tests, and CPU 
> utilization is much, much much higher in FreeBSD as well).
>
> I think you nailed the biggest source of overhead, but there is apparently a 
> lot more performance that we can get out of the hardware. I'd love to see 
> you commit this.

I can't remember if I pointed you at this before, but I remember us talking 
about it by e-mail.  What happens to your loopback performance if you compile 
PREEMPTION out of the kernel?

Robert N M Watson

>
> Drew
>
> x loopback_rr.after
> + loopback_rr.rhel4
> +--------------------------------------------------------------------------+
> |   x                                                                   +  |
> |x  x  xx                                                          +   ++ +|
> | |_MA__|                                                            |_AM_||
> +--------------------------------------------------------------------------+
>    N           Min           Max        Median           Avg        Stddev
> x   5      38590.71      40167.44      39301.22      39463.23      645.1375
> +   5      53349.28      54884.98      54388.49     54274.174     566.90395
> Difference at 95.0% confidence
>        14810.9 +/- 885.686
>        37.531% +/- 2.24433%
>        (Student's t, pooled s = 607.282)
>
>
> x 10GbE_rr.after
> + 10GbE_rr.rhel4
> +--------------------------------------------------------------------------+
> |  x                                                                    +  |
> |xxx                                                            +   +   + +|
> | AM                                                              |___A_M_||
> +--------------------------------------------------------------------------+
>    N           Min           Max        Median           Avg        Stddev
> x   6      33323.05      33703.95      33614.14     33556.268     137.33838
> +   5       43448.3      44966.41      44610.41     44331.738     606.53307
> Difference at 95.0% confidence
>        10775.5 +/- 571.321
>        32.1116% +/- 1.70258%
>        (Student's t, pooled s = 417.112)
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