James Wilkinson wrote:
Patrick Barnes wrote:
You are free to uninstall the SMP kernel packages. Unless you have
multiple processors, you'll actually get better performance using the
'normal' kernel. If your processor has 'hyperthreading' or a similar
feature, you might want to consider disabling it. Hyperthreading will
look like multiple processors to the kernel, and the SMP kernel will try
to take advantage of it, but this will actually usually result in a
small performance hit, depending upon how you use your system. Without
the SMP kernel, you will get no benefit at all from the hyperthreading
technology.
I'd be interested to hear what you base this on.
As I understand it, performance with or without hyperthreading on a
Pentium 4 depends on what you're doing to it and (to an extent) the age
of the system (it took Intel a while to really tune hyperthreading).
But hyperthreading is supposed to speed up a system, and often does.
Many people have reported interactivity benefits (the system responds to
interaction faster) even without seeing a total throughput benefit. So
for example, compressing a number of sound files while watching a video
might take the same time with or without hyperthreading, but (for
example) screen updates might be faster with hyperthreading.
Some sites that back my position:
http://www.2cpu.com/articles/41_1.html
http://www.anandtech.com/linux/showdoc.aspx?i=2213&p=5
From my experience, also, the smp kernels have APIC interrupts enabled,
whereas the standard uni-processor ones do not. This is especially
useful if you have a few cards that need to have interrupts serviced
frequently, like disk controllers/ethernet controllers, etc. I have one
system that when it is running in XT-PIC mode ( cat /proc/interrupts )
runs like a dog (ok... a dachshund) , but with APIC turned on, runs more
like a greyhound.
Steve
