[CentOS] CentOS 4 and Intel P4 without Hyper-Threading vs. IntelP4 with Hyper-Threading
Aleksandar Milivojevic
amilivojevic at pbl.ca
Wed Apr 20 16:09:58 UTC 2005
Robert Hanson wrote:
> Are you saying that the standard stock CentOS 4 kernel does not recognize
> nor use or take advantage of HT on a stand alone Intel processor and
> motherboard? This is a 865PERL w/LAN I use for development and testing...
There are two "standard" kernels distributed with every Red Hat system
(CentOS being clone of RHEL). One without SMP support, and one with SMP
support. The reason is that SMP support adds additional overhead to the
kernel (access to kernel structures must be locked, and so forth). Most
people are running UP machines, and therefore benefit from running
kernel that is optimized for UP machines.
If you install CentOS on UP machine, Anaconda (that's the installer)
will install only "kernel" package (the kernel optimized for UP
machines, no SMP support). If you install CentOS on SMP machine or on
UP P4 HT machine, Anaconda will install both "kernel" and "kernel-smp"
packages, and make SMP kernel default.
So, to answer you question. Yes. By default it will take advantage if
you initally installed it on SMP machine. If you installed on UP
machine, and later on moved disks to SMP machine, you need to manually
add kernel-smp package (not a big deal, rather trivial to do).
BTW, do note that HT processor still has only single core. Some reports
indicate that there's not much advantage of HT over non-HT processors
(and consequently not much advantage of running SMP kernel on HT
processor). Your "two virtuall" processors are still running on single
core. The real thing (dual-core processors) is something Intel has
announced to start shipping in near future. Up until now, dual cores
were limited to RISC processors such as UltraSPARC and Alpha.
--
Aleksandar Milivojevic <amilivojevic at pbl.ca> Pollard Banknote Limited
Systems Administrator 1499 Buffalo Place
Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
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