Re: MYSQL,Linux & large threads number

[Sinisa Milivojevic]

Peter Zaitsev writes:
> Hello mysql,
> 
>   Some time ago I wrote about slow down of mysql with large number of
>   threads, which is quite common in Linux-Apache-Mysql-PHP enviroment.
> 
>   The test was simulating the worst case of concurrency - all the
>   threads are modified global variable in a loop 5000000 times in
>   total, using standard mutex for synchronization. The yeild is used
>   in a loop to force even more fair distribution of lock usage by
>   threads and increase context switches, therefore it did not change
>   much with large number of threads. I.e with 64 threads time without
>   yeild is 1:33.5
> 
>   Test was run on PIII-500 1G RAM Kernel 2.4.18. 3 runs were made for
>   each number of threads and best results were taken:
> 
>  Num threads.       Time      Peak cs rate.
>     2               53.4          179518
>     4               53.8          144828
>     16              1:06.3         85172
>     64              1:48.1         48394
>     256             8:10.6         10235
>     1000           36:46.2          2602
> 

I hope you are using latest glibc 2.2 with our patches applied.

Also please try adaptive mutex. How to set it, take a look at
mysys/my_thr_init.c.

-- 
Regards,
   __  ___     ___ ____  __
  /  |/  /_ __/ __/ __ \/ /    Mr. Sinisa Milivojevic <[e-mail]>
 / /|_/ / // /\ \/ /_/ / /__   MySQL AB, Fulltime Developer
/_/  /_/\_, /___/\___\_\___/   Larnaca, Cyprus
       <___/   www.mysql.com