SMP Kernel on non-SMP Machine

[Matthew Miller]

On Wed, Aug 16, 2006 at 07:19:06PM -0700, W Strater wrote:
[confusing full-quoting snipped]
>> In fact, if your processor has the "nx" bit (look in the "flags") line in
>> /proc/cpuinfo, you will get a performance increase in system calls by using
>> the SMP kernel even on single-processor systems. I don't recall the
> Thanks for the help. The processor is a hyperthreading processor.

Okay -- that explains it. Hyperthreading is good for many workloads, but
actually a negative for others. If performance at a certain task is
important for you, try testing with it on and with it off and see which is
better. (It'll be a bios setting somewhere.)


> I do not have the "nx" flag in /proc/cpuinfo. Here is the output for one
> of the CPUs since the listing are virtually identical.

Okay. In that case, if you decide to not use hyperthreading, you may want
to use the non-smp kernel for a very marginal performance gain.

[...]
> I got my self into this problem because I downloaded kernel.devel to build
> a VPN client not realizing there was a separrate source code for the SMP
> kernel. Needless to say, I could not install the module I built and went
> looking for the culprit.

There is not a separate source code for the SMP kernel. It is simply a build
option.

What VPN client are you trying to build? Is it the glue layer for the Cisco
VPN client? If so, have you tried using the user-space and open source
"vpnc" instead?

-- 
Matthew Miller           mattdm at mattdm.org          <http://mattdm.org/>
Boston University Linux      ------>              <http://linux.bu.edu/>