From: Dan Nelson
Date: March 19 2003 4:01pm
Subject: Re: Process Limit on Linux ?
List-Archive: http://lists.mysql.com/mysql/135043
Message-Id: <20030319160138.GG91803@dan.emsphone.com>
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In the last episode (Mar 19), Philipp said:
> thank you for your answer. While i was reading about clustering some
> weeks ago i read the openmosix FAQ claiming that openmosix would not
> work with apache, because apache was using shared memory to
> communicate with its threads, and i always thought mysql is designed
> the same way. Please someone correct me if i am wrong.

SYSV shared memory (shm*) is a block of memory that one process
creates, and depending on the access flags, multiple processes can
attach to and see each other's changes.

Threads use shared memory by definition, because a threaded application
is still one process.  No SYSV shm tricks are needed.

Openmosix won't be able to balance mysql threads, because even if it
were possible to synchronize shared memory between machines with Mosix,
synching thread mutexes would be horrendously slow.  Better to just get
a multi-CPU box.

-- 
	Dan Nelson
	dnelson@stripped