From: Dan Nelson
Date: January 17 2002 11:06pm
Subject: Re: Memory
List-Archive: http://lists.mysql.com/mysql/96643
Message-Id: <20020117230606.GI84018@dan.emsphone.com>
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In the last episode (Jan 17), Jeremy Zawodny said:
> On Thu, Jan 17, 2002 at 04:37:40PM +0200, Heikki Tuuri wrote:
> > The maximum process space of Linux x86 is 2 GB, and better play
> > safe.
> > 
> > Jeremy, I think some Intel x86 processors support segmented memory
> > above > 4 GB. Is that supported in Linux?
> 
> Not sure.  Most of what I've heard has always come back to the 2GB
> limit for a single process.  There's probably some discussion of it
> in the linux-kernel archives.

You can shift the kernel/userland split point; make it 3gb userland,
1gb kernel, but you probably don't want to go any more than that.

Oracle has used multiple shared memory segments to allow a single
process to access more than 4GB of memory on a 32-bit machines for
years.  You allocate (say) 10 600MB segments, but only map two in at a
time.  This approach wouldn't work well for Mysql since it's a single
process.  Threads all share the same address space, so all the threads
would have to agree on which 2 segments to use at any point in time.

-- 
	Dan Nelson
	dnelson@stripped