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Re: Linux and Intel's Hyperthreading



On Tue, 31 Dec 2002 20:16:03 -0800 (PST)
"nate" <debian-user@aphroland.org> wrote:

| nick lidakis said:
| > I was looking to replace my 1Ghz P3 and motherboard with  a stable,  but
| > fast mb/cpu combo that was fully supported by a recent linux kernel. I
| > was looking a an Intel 845PE motherboard with a 3.0Ghz cpu. My question
| > is, how is Hyperthreading supported under linux? Is it a matter of
| > enabling SMP in the kernel? Anyone playing with one of these CPU's?
| 
| 
| it is supported by default. the system will see double the cpus there
| actually are. the kernel isn't tuned to fully take advantage of the
| hyperthreading yet though. I think newer 2.5.x kernels can do it, perhaps
| theres a patch for 2.4.x.. but last I read the current breed of stable
| kernels are not optimized for it.
| 
| If I had a system with hyperthreading I would disable the hyperthreading
| in the bios(one mailing list thread mentioned there is an option to do
| so, at least on some systems). Because the kernel would get confused and
| think there are 4 processors on a 2 processor system it might try to get
| smart by loading stuff up on processor #2, not knowing its the same physical
| processor as #1, before loading stuff on #3. I don't remember any benchmark
| numbers but I seem to recall there being very little if any difference
| in performance on hyperthreaded systems with hyperthreading on vs. off
| on the stock kernels(performance can go way up on the newer 2.5.x which
| are tuned to take advantage of it in some cases).
| 
| I've read one post on the redhat list recently, some guy was asking why
| top showed 4 cpus on his dual p4, since it was a dual cpu system, a guy
| responded because it was hyperthreading .......
| 
| so it should work, just not very optimal.
| 
| nate
| 
Well, ASUS suggest to compile with the Hyper-Threading compiler ???
What about this compiler ?
Thanks
mess-mate
-- 
Computers are like air conditioners, they are useless when you open
Windows.

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