[wlugkc] SMP Thoughts
- From: Robert Gambrill <robertgambrill@xxxxxxxxxxxxx>
- To: wlugkc@xxxxxxxxxxxxx
- Date: Wed, 18 May 2005 21:55:38 -0500
Hi All,
Got some data on going to multiple CPU's using linux-2.6.8 kernel
compiles as a benchmark.
I setup the new mainboard using my old 2.6.8 kernel, and redid the
'make menuconfig' to configure it for multiple CPU's. At this time I was
running with one CPU enabled. Using....
time sh -c 'make bzImage'
... I got aprox ~00:35:12 for the compile time.
I then did a make modules_install and setup the new kernel in lilo.conf.
Rebooted and verified that I had two CPU's running. Did another timed
'make bzImage' .
I got approx ~ 00:18:27 for the two CPU compile time. It took
about 52% of the time a single CPU would have taken. Thats about
what I expected, there has to be some overhead to using more than
one CPU. Still, It's a nice improvement.
OK, Today I recieved an adaptec 2940 U2W SCSI Controller I ordered. This
allows my Ultra 160 SCSI drives to talk at 80 MBs (Sync) on my 32bit PCI
bus ( My old 2940 Ultra Wide could only do 40 MBs ). You gotta have
PCI-Express (64-bit) to do Ultra 160 or Ultra 320.
Anyway I doubled my harddrive's bandwidth and recompiled the kernel
(same as before).
I got approx ~00:18:05 for the compile time. Not much improvement
(about 2%) but it showed up.
SO!
The Kernel compile is NOT I/O bound on my machine. It IS heavily CPU
bound, and would ( in my entirely unscientific opinon) benefit from a
set of newer CPU's. I imagine a lone modern CPU would
probably stomp this old board into the ground. I only bought it to play
with. I may upgrade the P3's to the max and see what
happens. Thats the fun thing about junkbox gear, It' cheap to get the parts!
Oh BTW, to do these tests you have to edit the make options. Make -jN
where N equals the number of CPUs +1 allows it to use
multiple CPU's.
I would like to hear, if you think about it, how long to takes to
compile your linux kernel on more modern equipment. Sorry, at this time
the only test I have to check out S.M.P. is a kernel compile. Will try
to see what improvement I get on doing something real world, oh
say for example, MPEG encoding, and let you guys know if anybody's
interested.
Robert
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