R help - Apr 2004 - openMosix vs SNOW: redhat kernel causing slowdown?

Hi there,

We're currently attempting to explain a slowdown of an LVQ-type parallel 
analysis we're working on.  We are benchmarking our analysis running 
over openMosix against the same running via SNOW for R.  Both perform 
similarly on small datasets, but on large datasets SNOW drastically 
outperforms openMosix.  However, these results are achieve running SNOW 
on the default RedHat kernel (Enterprise Edition, RHEL-3) and mosix on 
the same kernel patched with the rpm for RedHat 9 from sourceforge. 
 Even though the rpm seems to be compatible and everything runs fine, 
when the same SNOW analysis is run under the patched kernel there is an 
enormous slowdown in runtime, to the point that openMosix outperforms SNOW.

Is there some sort of incompatibility issue with the RedHat kernels 
(either general or specific to this version) that would cause a slowdown 
of this kind?  I know that Enterprise Edition was marketed as having 
tools to increase java clustering speeds, would this interfere with the 
type of socket communication SNOW uses?

Thanks,
Jim

You're using sockets for connection in snow?  or pvm or mpi?
There's nothing magical about snow.  It just uses the socket
connections provided in R, which in turn uses regular  BSD sockets.

-----Original Message-----
From: Jim Thomas [mailto:james at staarfunds.com] 
Sent: Thursday, April 29, 2004 6:13 PM
To: r-help at stat.math.ethz.ch
Subject: [R] openMosix vs SNOW: redhat kernel causing slowdown?


Hi there,

We're currently attempting to explain a slowdown of an LVQ-type parallel 
analysis we're working on.  We are benchmarking our analysis running 
over openMosix against the same running via SNOW for R.  Both perform 
similarly on small datasets, but on large datasets SNOW drastically 
outperforms openMosix.  However, these results are achieve running SNOW 
on the default RedHat kernel (Enterprise Edition, RHEL-3) and mosix on 
the same kernel patched with the rpm for RedHat 9 from sourceforge. 
 Even though the rpm seems to be compatible and everything runs fine, 
when the same SNOW analysis is run under the patched kernel there is an 
enormous slowdown in runtime, to the point that openMosix outperforms SNOW.

Is there some sort of incompatibility issue with the RedHat kernels 
(either general or specific to this version) that would cause a slowdown 
of this kind?  I know that Enterprise Edition was marketed as having 
tools to increase java clustering speeds, would this interfere with the 
type of socket communication SNOW uses?

Thanks,
Jim

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