dual cpu act like a 4 cpu (intel SE7500CW2)

dual cpu act like a 4 cpu (intel SE7500CW2)

Post by Neil McFadye » Thu, 14 Nov 2002 04:45:53



Dual Zeon Intel SE7500CW2 brd   (Intel E7500 chipset)

on boot up the bios indicates 4 cpus
redhat 8.0 appears to think it 4 cpus rather than 2 and it runs as if it
has 4

The user wrote a small program that takes about 18 seconds to
execute when it has a CPU all to itself.  I then ran either 1, 2, 3, 4,
6,
or 8 copies at the same time, but "timed" one of them.  If I have 2
processors used to their max speed, I should see a drop off in speed for

more than 2 jobs.  But I don't.  Up to 4 jobs simultaneously take
essentially the same amount of time (see results below).

Results:

output from the command "time a.out" depending on number of jobs running

simultaneously.  "real" time is the one that matters.  "user" time,
whatever that means, scales linearly with the number of jobs.

one
real    0m18.642s
user    0m18.621s
sys     0m0.002s

two
real    0m19.657s
user    0m39.301s
sys     0m0.004s

three
real    0m22.032s
user    1m2.713s
sys     0m0.004s

four
real    0m21.975s
user    1m28.033s
sys     0m0.186s

six
real    0m31.030s      (about 1.5 times normal.  makes sense for 4 CPUs)

user    1m51.297s
sys     0m0.109s

eight
real    0m41.468s      (about 2.0 times normal.  again, looks like 4
CPUs)
user    2m57.570s
sys     0m0.539s

same thing with Win XP - 4 cpus show up in task manager

Neil

 
 
 

dual cpu act like a 4 cpu (intel SE7500CW2)

Post by Mark Taylo » Thu, 14 Nov 2002 06:19:13




Quote:> Dual Zeon Intel SE7500CW2 brd   (Intel E7500 chipset)

> on boot up the bios indicates 4 cpus
> redhat 8.0 appears to think it 4 cpus rather than 2 and it runs as if it
> has 4

> The user wrote a small program that takes about 18 seconds to
> execute when it has a CPU all to itself.  I then ran either 1, 2, 3, 4,
> 6,
> or 8 copies at the same time, but "timed" one of them.  If I have 2
> processors used to their max speed, I should see a drop off in speed for

> more than 2 jobs.  But I don't.  Up to 4 jobs simultaneously take
> essentially the same amount of time (see results below).

> Results:

> output from the command "time a.out" depending on number of jobs running

> simultaneously.  "real" time is the one that matters.  "user" time,
> whatever that means, scales linearly with the number of jobs.

> one
> real    0m18.642s
> user    0m18.621s
> sys     0m0.002s

> two
> real    0m19.657s
> user    0m39.301s
> sys     0m0.004s

> three
> real    0m22.032s
> user    1m2.713s
> sys     0m0.004s

> four
> real    0m21.975s
> user    1m28.033s
> sys     0m0.186s

> six
> real    0m31.030s      (about 1.5 times normal.  makes sense for 4 CPUs)

> user    1m51.297s
> sys     0m0.109s

> eight
> real    0m41.468s      (about 2.0 times normal.  again, looks like 4
> CPUs)
> user    2m57.570s
> sys     0m0.539s

> same thing with Win XP - 4 cpus show up in task manager

> Neil

Is there a question i all of this? It looks like Xeon hyperthreading to me.

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dual cpu act like a 4 cpu (intel SE7500CW2)

Post by mjt » Thu, 14 Nov 2002 07:20:28



> on boot up the bios indicates 4 cpus
> redhat 8.0 appears to think it 4 cpus rather than 2

... never saw a question ... look up "hyperthreading" here:
http://www.google.com/linux

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Michael J. Tobler: motorcyclist, surfer,  #    Black holes result
 skydiver, and author: "Inside Linux",     #   when God divides the  
 "C++ HowTo", "C++ Unleashed"              #     universe by zero

 
 
 

dual cpu act like a 4 cpu (intel SE7500CW2)

Post by Lee Sau Da » Wed, 20 Nov 2002 18:28:40


    Neil> The user wrote a small program that takes about 18 seconds
    Neil> to execute when it has a CPU all to itself.  

I  don't even  need to  write a  program.  A  "gzip -9  <  /dev/zero >
/dev/null" already  does that.  For  finite sessions, get  just enough
number of  bytes with "dd if=/dev/zero bs=1M  count=16", for instance.
:)

    Neil> I then ran either 1, 2, 3, 4, 6, or 8 copies at the same
    Neil> time, but "timed" one of them.  If I have 2 processors used
    Neil> to their max speed, I should see a drop off in speed for
    Neil> more than 2 jobs.  But I don't.  Up to 4 jobs simultaneously
    Neil> take essentially the same amount of time (see results
    Neil> below).

Google Hyper-threading.

--


Home page: http://www.informatik.uni-freiburg.de/~danlee

 
 
 

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