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  • From: qwms-avib AT dea.spamcon.org
  • To: baslinux AT lists.ibiblio.org
  • Subject: Re: [BL] openMosix on BL2
  • Date: Wed, 30 Jul 2003 18:55:32 +1200

I've now been doing some compiling on my openMosix cluster
(two BL2 computers). I ran the compiler on the slower
machine and ran mosmon on the faster machine. The results
were educational.

During the first run, process migration was sporatic and
short-lived. Processes seemed reluctant to leave the home
node and returned quickly. Overall, the compiling time was
only slightly improved. So for the second run I decided
to try something I had read in the openMosix documentation.
Apparently some processes don't migrate well because they
keep returning to reference the home filesystem. The way
around this is to create a unified filesystem where each
node can access all the other's files. The openMosix kernel
(at basiclinux.com.ru) has this capability, but you have to
turn it on. So, I turned it on and ran the compiler again.
The difference was immediately noticeable. I could see in
mosmon that more processes were migrating and (more important)
they were spending longer away from home. Compiling time was
cut nearly in half.

Having a unified filesystem is kind of spooky. You can move
a file from any computer to any other computer simply by
copying it from one directory to another. So, on a three-
node cluster, you could enter a command on node-2 that moves
a file from node-1 to node-3.

I won't be putting a unified filesystem in the default open-
Mosix package for BL2. It's too risky. For example, it
appears that a careless rm on one of the nodes could wipe
every system in the cluster (I haven't tried this). However,
the unified filesystem is an option for anybody who finds
that the default openMosix isn't performing well enough.

Cheers,
Steven





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