In the last episode (Sep 10), [EMAIL PROTECTED] said:
> I'm stumped at how little improvement using an SMP kernel gives in a
> Dell 2650. System is dual 2400 xeon processors, 2 GB ram. It's
> intended to be used as a database processor, among other things. A
> perl process that read and input file and updates simple records in a
> mysql database actually run much more slowly: processing ~2million
> records takes 817 seconds with SMP enabled and 262 seconds with it
> disabled.
>
> Simple things like some_program.pl < some_big_file | another_program.pl
>
> seem to take full advantage of the second processor, but this system
> is supposed to run mysql.
Mysql is a threaded database, and FreeBSD's pthreads are user-space.
This means that mysql will only ever use one CPU, and disk I/O in one
thread will block all other threads.
You can try:
* Rebuilding the mysql port with USE_LINUXTHREADS=yes. This will help
lots if your mysql process is CPU-bound, and will help some if you
are heavily I/O bound.
* Switching to InnoDB tables, which cache much better than MyISAM
tables so you are more likely to get your data from RAM instead of a
blocking disk read.
* Splitting your single perl program into multiple ones that hit the
database simultaneously. You might be seeing a synchronization
effect where your perl and mysql processes are competing for a SMP
lock or something and the wrong one always wins.
--
Dan Nelson
[EMAIL PROTECTED]
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