[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: wthere my SMP working or not?



cwinl wrote:
> ooh my.
> You mean that my 4 CPUs already  work ?

You did not expect them to?

Personally I always check /proc/cpuinfo.

  cat /proc/cpuinfo

> but redhat's command top would display 4 CPUs message lines on the
> top of the message.  i mistake ? i use debian just 1 week. redhat is
> my OS before.

Red Hat's top command is broken when you add more cpus.  Having
multiple "CPU states" lines will in that case consume all of the
available screen space and leave no room to show the top cpu
processes.  Linux has run on machines with hundreds of cpus.  Red
Hat's top does not scale there.

  http://bugs.debian.org/62282

I recommend 'xosview' if you want to see more individual information
about your system.

If you really have two cpus then I would turn hyperthreading off.  My
benchmarks show terrible interactions when running multiple processes.
HT is probably fine on a uniprocessor machine.  But consider two tasks
running on a dual cpu with HT enabled.  The first two cpus will both
pick up one task each.  But wait.  The first two cpus are really HT'd
on the same cpu.  So now your first two tasks run at half speed both
on the first cpu and the second of your cpus remains idle.  Things get
strange with an odd number of tasks too.  If you really have multiple
cpus then I don't see any advantage of HT.

This is with the linux-2.4 kernel.  I don't know if linux-2.6 improves
upon the situation.  But I don't see how it could since HT is by
design transparent.

Bob

Attachment: pgpCGXJhgYHrK.pgp
Description: PGP signature


Reply to: