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From:Michael Widenius Date:December 12 2000 12:54pm
Subject:Re: SMP & MySQL under FreeBSD
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>>>>> "Antony" == Antony T Curtis <antony@stripped> writes:

Antony> Michael Widenius wrote:
>> Hi!
>> >>>>> "Rick" == Rick Jansen <Rick@stripped> writes:
Rick> Hi.
Rick> My MySQLd is using just one CPU in FreeBSD. How can i fix this? Running
Rick> multiple mysqld's isn't an option, all databases are somewhat related and
Rick> connected to eachother.. I've tried installing LinuxThreads, which went
Rick> well, but now mysql won't compile. Any hints and/or tips would be GREATLY
Rick> appreciated..
Rick> Rick Jansen
>> FreeBSD doesn't support multi-CPU:s for a threaded program yet (this
>> should hopefully been fixed soon).  I haven't yet heard about anyone that
>> has got LinuxThreads to work good on FreeBSD so unfortunately your are
>> on your own regarding this :(
>> Tim suggested that you could try to run the MySQL-Linux binary on
>> FreeBSD under Linux emulation, but this is only a wild guess...

Antony> This is a way but not ideal. Linux threading model is very heavyweight
Antony> so you have a performance drop from that. Linux does not scale to very
Antony> many threads due to it's threading model using process ID's.

In practice the above is not really true;   Linux 2.4 seams to scale
very well with threads (we have tested this with 2000 threads).

The major performance problem with Linuxthreads is the mutex
implementation, not the clone model.

(I would however agree that it's much better to support threads in the
kernel, but more for management reasons than for performance reasons)