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simply put, how do I disable Hyperthreading?

post #1 of 19
12/3/03 at 8:22pm
Thread Starter 
I have a Sager 8890 laptop. Its a psycho notebook, a true desktop
replacement. It uses an i856 SpringDale chipset. You should consider it the
same as a desktop for all intents and purposes, though it does have a
battery. I have a 2.6 Mhz processor running at 800Mhz FSB. Its also
Hyperthreading compatible.

For reference:
http://pctorque.com/pre-notebook.php#8890
and
http://talknotebooks.com/showthread....&threadid=6481

I am currently running the Distributed.net client which is trying to crack the
RC5-72 bit cipher. Its one of those background programs that runs low
priority, but consumes all unused CPU cycles.

For reference:
http://n0cgi.distributed.net/faq/ind...&threadid=6481

Now I have conducted some of my own tests and I find that when running in
hyperthreading mode, my performance drops off considerably relative to a
single processor environment. Let me provide you with an example of the
rc5-72 client log files:

One processor:
[Sep 16 06:21:33 UTC] RC5-72: Summary: 2 packets (2.00 stats units)
0.00:31:33.12 - [3,540,605 keys/s]

Two processor: (Hyperthreading)
[Nov 04 18:25:37 UTC] Automatic processor detection found 2 processors.
[Nov 04 18:38:37 UTC] RC5-72: Completed CA:6AB5BFD0:00000000 (1.00 stats
units)
0.01:24:31.91 - [846,827 keys/s]
[Nov 04 18:38:37 UTC] RC5-72: Loaded CA:6AB5BFD2:00000000:1*2^32
[Nov 04 18:38:37 UTC] RC5-72: Summary: 3 packets (3.00 stats units)
0.02:23:27.42 - [1,277,942 keys/s]
[Nov 04 18:44:06 UTC] RC5-72: Completed CA:6AB5BFD1:00000000 (1.00 stats
units)
0.01:25:03.30 - [841,618 keys/s]
[Nov 04 18:44:06 UTC] RC5-72: Loaded CA:6AB5BFD3:00000000:1*2^32
[Nov 04 18:44:06 UTC] RC5-72: Summary: 4 packets (4.00 stats units)
0.02:28:56.42 - [1,711,515 keys/s]

After each key is completed, the client provides a benchmark statistic. With
1 processesor, I get a 3.5 Mk/s and with the HT score, each virtual processor
is doing about .8 Mk/s. When added together they average at about half if
hyperthreading were disabled!

Has anyone done other benchmarks on highly computational processes and seen
performance losses with and without hyperthreading? Currently, I think its
ho-key crap and some of the benchmarks I have seen have only had ~10%
improvement on multi-threaded processes. Well, clearly, this RC5-72 client
is very multi-thread and it takes a serious performance hit.

So I have this laptop, and its on all the time. Its got Mandrake 9.2 on. In
the lilo.conf file, the Enterprice kernel I run has the following parameters:

image=/boot/vmlinuz-enterprise
label="linux-enterpris"
root=/dev/hda2
initrd=/boot/initrd-enterprise.img
append="devfs=mount hdg=ide-scsi acpi=ht splash=silent"
read-only

What do I change to disable Hyperthreading?

Results you might have already thought of:
If I removed the acpi=ht value, no difference.
If I go into the BIOS and disable Hyperthreading, the laptop can't unpack the
kernel.
If hyperthreading is disabled in BIOS, and I insert the install CD, it also
can't unpack the kernel.
You look at the Mandrake Errata which covers HT problems:
http://www.linux-mandrake.com/en/errata.php3#nolapic
It states to add 'nolapic' to your kernel flags, well that does squat.

Make this real easy for me. What should I put into the apostrophes:
append=" "

I place your answer into my kernel flags, go into BIOS, disable HT, and then
boot that kernel. If that could work, I'd be overjoyed. I've been
scratching my head on this one for a long time. I sure hope someone can help
me out.

-Lox Thomson
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post #2 of 19
12/5/03 at 3:40pm
v8esprit :

Well you have the right solution. HT uses the SMP linux kernel. So under ur present running configuration, dll the sources of the kernel you are running from mandrake. Do not go to kernel.org, as the vanilla kernel will not have the mandrake patches, and as i know vendor distributions, ya have a good chance to boot but break lots of your apps / scripts / functionnality. cd to that source dir, make menuconfig and under processor features, disable the SMP option. exit . save, make (dep if 2.4.X) bzImage modules modules_install install [enter] and watch it compile and install. Then edit lilo / grub reboot that, disabling HT in the bios before.

BTW, i have a p4 2.4 at 533 NON ht, and will love to swap heh = )
hehehehe.
Good luck.
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post #3 of 19
12/5/03 at 5:14pm
Can't you just disable it in your BIOS before loading your OS?

-myrkat
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post #4 of 19
12/5/03 at 5:36pm

Linux ...

myrkat:
Linux doesn't blindly follow the Bios as windows does. If the linux kernel has SMP / ht compiled in, it will RE eanble what the bios has disabled. Hence why he needs a kernel recompile.
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post #5 of 19
12/5/03 at 6:16pm
Thread Starter 
Yea Myrkat,
Like I mentioned above, if I disable HT in the BIOS, Linux won't boot. Its a black screen. I'm gonna do the recompile and I'll report back.

Anyone see advantages with HyperThreading? I think its a farce.

-Lox
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post #6 of 19
12/5/03 at 7:35pm
Quote:
Originally Posted by v8esprit
Yea Myrkat,
Like I mentioned above, if I disable HT in the BIOS, Linux won't boot. Its a black screen. I'm gonna do the recompile and I'll report back.

Anyone see advantages with HyperThreading? I think its a farce.

-Lox
I see advantages in it when doing MPEG compression of videos and what-not (under windows)... for instance, Material for DVD-authoring compiles faster (though I've not timed it, so it could be an illusion) than a non-HT system.

Under *nix, I dunno... it takes a lot of doing to get linux distro's "snappy" and I don't have that much time, patience or experience to tinker. I'd love to hear the more experienced *nix users' take on this, however.

-myrkat
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post #7 of 19
12/7/03 at 1:06pm

Ht

Well, hehehe, i would love to tell my point of view unfortunately, i have a non HT processor...So far the improvement given by benches on linux shows a 2 to 15 % perf on certain tasks but as well an under perf on others.
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post #8 of 19
12/8/03 at 1:22pm
Alrighty just my 2c worth.

1) Get the vanilla kernel - the mandrake kernel has patches in it yes - the main one being the supermount stuff - its not worth it in my opnion. If you ever want to patch your kernel outside of mandrake, chances are the patch will work only against the vanilla kernel. I run Mandrake and speak from experience.
2) HT under linux has its pro's and cons depending on what you are going to do. If you are compiling then HT is a boon - if you are encoding Divx etc then HT is not so great as this kind of thing (using transcode) uses only one of the virtual CPU's effectively. This has a proviso though. If you are doing pre and post processing such as deinterlacing plugins etc - then the HT will once again be a bonus.

Most things under linux will take advantage of the HT. For me its worth it. Your mileage may vary
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post #9 of 19
12/31/03 at 6:00pm
If you really want to see improvements with hyperthreading, use a 2.6 kernel and either:

Use Con Kolivas's kernel patches for interactivity (O21 is the current, I think), as well as his HT patches and HT-enabled batch scheduling patches, or

use Nick Piggin's SMP/NUMA kernel patches (w27 is the current) with hyperthreading aware scheduling.

http://kernel.kolivas.org
http://www.kerneltrap.org/~npiggin/
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post #10 of 19
12/31/03 at 6:17pm
I second that. The scheduling in 2.6 makes the entire desktop seem much more "snappy".
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post #11 of 19
1/5/04 at 4:37pm
Gee I can {dis|en}able hyperthreading on my 4780 and OpenBSD boots just fine either way.
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post #12 of 19
1/5/04 at 6:00pm
Quote:
Originally Posted by marten
Gee I can {dis|en}able hyperthreading on my 4780 and OpenBSD boots just fine either way.
Why wouldnt it? Linux is not some crappy OS like Windows that needs a complete reinstall to see the HT. You simply need it in the kernel. If its their the kernel will use it - if its not it wont.
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post #13 of 19
1/5/04 at 7:26pm
>Linux is not some crappy OS like Windows t
^^^^^^^^^^^^^^^^^
Opinion. YMMV, toughguy.
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post #14 of 19
1/5/04 at 9:59pm
Sorry I am way behind on my FUA (F**kin Useless Anagram) technology - what is YMMV?
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post #15 of 19
1/7/04 at 5:22am
He means "Your Mileage May Vary."

But I have agree with Bratag here. The fact that windows only installs either a uniprocessor or multiprocessor kernel based on what it detects is bad enough, but the fact that the multiprocessor kernel _cannot_ operate with only a single processor is even worse. The linux SMP kernel operates just the same whether it's running on one or more processors. They even recommend now that you use an smp kernel in linux regardless of how many processors you have.

Here's a question: what happens if you're running a multiprocessor windows system, and one of your processors toasts itself in the middle? You _can't_ use the windows install again unless you buy a replacement processor or you reinstall. Some of us don't have money readily available like that.
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post #16 of 19
3/23/04 at 3:49pm
Quote:
Originally Posted by marten
Gee I can {dis|en}able hyperthreading on my 4780 and OpenBSD boots just fine either way.
I just had to register just to call bull**** on this statement. The reason OBSD boots with ht enabled or not enabled is because up until about a few weeks ago, OpenBSD didn't even support SMP!! And it is just past the PRE-development stages! Don't get me wrong, I was once a OBSD purist, but its theocracy killed that.

-L
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post #17 of 19
3/23/04 at 3:59pm
Well wouldnt that be based on the kernel etc he was running in OBSD? For all you know he might be running a beta version of a newer OBSD kernel. Its a shame your very first post on the board had to be a flame and makes you sound like a petulant dick.
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post #18 of 19
3/23/04 at 5:18pm
Quote:
Originally Posted by Bratag
Well wouldnt that be based on the kernel etc he was running in OBSD? For all you know he might be running a beta version of a newer OBSD kernel. Its a shame your very first post on the board had to be a flame and makes you sound like a petulant dick.
No, you don't understand, there is no working SMP kernel for OpenBSD . And that was not a flame, but an obvious bull**** call on a troll. If anything I should be smacked for feeding the troll, not being a "petulant dick".



-L
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post #19 of 19
3/23/04 at 5:21pm
Well guess I owe you an apology - your first post just seemed like a flame.
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