Pentium 4 HT - No activity on CPU1?

Accipiter

I am running Linux, more or less perfectly, on a Dell Inspiron 9100, with the exception of an unsupported minor feature here or there. It uses a Pentium 4 processor with hyperthreading. I've compiled the following support into my kernel (gentoo-dev-sources-2.6.9-r9 patched with swsusp2.1.5):

truekaiser · l33t Joined: 05 Mar 2004 Posts: 810

you do realize ht is more marketing hype then an actual usefull feature?

Accipiter · Posted: Wed Feb 09, 2005 3:38 am Post subject: -_-;

I'll have won the lottery the day someone is able to mention HT on these boards without having the Flamerod of Marketing Hype +1 shoved up their...

Thank you for wasting my unanswered post status.

arkhan_jg · Posted: Sun Feb 13, 2005 2:44 pm Post subject: test multithreading?

Have you tried something definitely parallizable?

i.e. set MAKEOPTS="-j3" in your make.conf, then check top while you do an emerge -u world. Not all packages can take advantage of the multiple threads while compiling, so run a few through to check.

It's worth pointing out that not all apps can take advantage of multithreading; the scheduler, low-level kernel primitives, the file server, the network, and threaded apps should however be able to.

If compiling still doesn't use CPU 1, you'll need to look deeper. You could try running dbench with HT compiled in and not, to see if HT is being used, just transparently. It might also be worth switching to NPTL, if you haven't already, given the better thread handling it includes. Also, if you've got a single-thread process taking up a lot of CPU, I don't think the scheduler will move stuff to CPU1 as that would take away execution units from the first non-threaded process.

http://www-128.ibm.com/developerworks/linux/library/l-htl/ might be an interesting place to start looking deeper into some tests you can run.

Oh, nearly forgot. The slower/older P4's have HT on the chip, but it's disabled for marketing reasons. Which P4 have you got, is it definitely a HT-enabled one (3.0 GHz or better, IIRC). See http://forums.2cpu.com/showthread.php?s=&threadid=34330 for more details on how HT works.
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make menuconfig not war