PTHREAD_YIELDLOOPS boosts mysql super-smack performance

[David Xu]

I did a simple mysql super-smack benchmark test on a Intel XEON machine,
the CPU has 4 cores:
    CPU: Intel(R) Xeon(R) CPU            5130  @ 2.00GHz (1997.03-MHz)


I have set environment variable LIBPTHREAD_YIELDLOOPS to 30 and start 
mysql server:

setenv LIBPTHREAD_YIELDLOOPS 30
/usr/local/etc/rc.d/mysql-server start

and repeat doing
#super-smack ./select-key.smack 10 20000

The result is very surprising:

# /usr/src/tools/tools/ministat/ministat normal.txt yield_30.txt

x normal.txt
+ yield_30.txt
+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
|  x  x x 
                                              + 
              |
|  x xxxx 
                                         + + ++ 
              |
|x x xxxxx x 
                                       + + + ++        + 
              |
|x x xxxxxxx   x      x 
                +                    + + ++++++ ++++ +++  ++ 
             +|
|  |___A___| 
                                    |________M_A_________| 
              |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------+
     N           Min           Max        Median           Avg        Stddev
x  30      44790.57      48609.38     45831.065     45910.616     745.54679
+  30      60521.95       73090.6     66008.135     66254.815     1953.4324
Difference at 95.0% confidence
         20344.2 +/- 764.241
         44.3126% +/- 1.66463%
         (Student's t, pooled s = 1478.47)

it seems over 44% performance is improved.


Regards,
David Xu