Baslinux mailing list

[qwms-avib AT dea.spamcon.org]

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