SMP Kernel on non-SMP Machine

[W Strater]

Message: 6
Date: Wed, 16 Aug 2006 16:23:18 -0400
From: Matthew Miller <mattdm at mattdm.org>
Subject: Re: SMP Kernel on non-SMP Machine
To: For users of Fedora Core releases <fedora-list at redhat.com>
Message-ID: <20060816202318.GC18410 at jadzia.bu.edu>
Content-Type: text/plain; charset=us-ascii

On Wed, Aug 16, 2006 at 02:09:20PM -0600, Ski Dawg wrote:
> Now, we used to do this at work (on RHEL) without any problems. We also
> installed the SMP kernel on machines that were single processor with no
> hyperthreading. We did this so that developers were working with the
> same kernel, no matter which machine they were using. Everything ran
> just fine with the SMP kernel on all the machines.

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
particulars of this, but there was a thread on fedora-devel a while ago
about it if you care to search. (This is one reason SMP is enabled in all
kernels in FC6.)


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


Thanks for the help. The processor is a hyperthreading processor.

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.

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.80GHz
stepping        : 5
cpu MHz         : 2793.303
cache size      : 512 KB
physical id     : 0
siblings        : 2
core id         : 0
cpu cores       : 1
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr
bogomips        : 5586.39

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.

Wes.




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