Semetric processing and TOP.

[Neil Marjoram]

I have just commissioned a 2 x Xeon 2.8Ghz 512MB 533Mhz FSB compute node
for research work. I have just been told it's much slower (around 25%
slower) than a single processor P4 2.8 Ghz 512MB 533Mhz FSB tower PC.

The processes run on a single CPU are not multi-threaded, uses very
little disk IO (there is no io wait), and little memory. The process
simple reads a file and does a number of calculations on that file and
then writes out a simple text file, and then repeats for the next file.
The calculations are complex and the process often lasts hours and
sometimes days.

Running two processes in the twin Xeon seems to be around 25%-50% slower
than running a single process in the P4 tower PC. Is this what I should
expect give that the bus configuration in the Xeon is not any better
than the P4 PC?

Also I note from the output from top that the two processes each consume
99.9% of CPU, but the total user at the top is 50%, and the idle is 50%.

vmstat gives this output, which backs up the top output:

procs ------memory-------- ---swap-- -----io---- --system-- ----cpu----
 r b swpd free  buff  cache   si   so    bi    bo   in  cs us sy id wa
 2  0 0 238124 134148  46812    0    0  0     0    7     0 50  0 50  0
 2  0 0 238124 134148  46812    0    0  0    12 1010    14 50  0 49  1
 2  0 0 238124 134148  46812    0    0  0     0 1004     7 50  0 50  0
 2  0 0 238124 134148  46812    0    0  0     0 1005     7 50  0 50  0
 2  0 0 238124 134148  46812    0    0  0     0 1004    11 50  0 50  0
 2  2 0 238124 134156  46804    0    0  0    19 1007    19 50  0 49  1
 2  0 0 238124 134156  46804    0    0  0     1 1007    14 50  0 48  2

I know the two processes are not swapping CPU's but can't see what may
be causing the 50% idle time, as I do not know what the process is
waiting for. On the P4 2.8 tower there is no idle time at all.

OS - FC2 patched to everything available beginning of last week!

Am I missing something? (Brain?)

Anybody have any opinions on this?


Thanks,


Neil.

-- 
Neil Marjoram.
Systems Manager
University College London
Adastral Park Campus
Martlesham Heath
Ipswich
Suffolk
IP5 3RL

01473 663711