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

[Andrew Gallatin]

Poul-Henning Kamp writes:
 > In message <17388.44976.250463.383429 at grasshopper.cs.duke.edu>, Andrew Gallatin
 >  writes:
 > 
 > >Here are some benchmark results from my "AMD Athlon(tm) 64 X2 Dual
 > >Core Processor 3800+" running an SMP kernel for both loopback and
 > >10GbE TCP networks.  The executive summary is that there's a 41%
 > >improvement in loopback pingpong, and a 12.5% improvement in a
 > >pingpong test with a remote linux machine over 10GbE.  Since the linux
 > >machine isn't infinately fast, the improvement is probably a bit more
 > >than 12.5% ;)
 > 
 > That's a LOT more than I had hoped for...

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.

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)