On Thu, Sep 18, 2003 at 03:24:31AM -0500, Peter Seebach wrote:

> I know that, on some systems, a P4 with hyperthreading looks like two
> processors.  Should this be working on NetBSD-current?  Is it useful?
> I know it works in BSD/OS, and I also hear that the net performance gain
> is typically negative.  :)

Here's some tests I ran on a dual 2.8GHz Xeon around the end of June,
using "./build.sh release":

	1 CPU     3867.442u  738.180s 1:20:32.44  95.3%
	1 CPU -j2 4056.016u  858.126s 1:19:57.97 102.4%
	2 CPU     3961.342u 1020.396s 1:24:59.30  97.6%
	2 CPU -j2 4245.934u 1283.933s   56:41.13 162.5%
	2 CPU -j4 4451.800u 1451.676s   54:28.01 180.6%
	4 CPU     4734.427u 1481.303s 1:26:14.59 120.1%
	4 CPU -j2 5125.070u 1750.326s 1:01:33.84 186.1%
	4 CPU -j2 5156.206u 1741.361s 1:02:17.22 184.5%
	4 CPU -j4 7638.933u 3006.625s   54:48.12 323.7%
	4 CPU -j8 8346.961u 3559.969s   54:53.70 361.5%

"1 CPU" was a UP kernel, "2 CPU" was with HT disabled in the BIOS,
and "4 CPU" was HT enabled.  All of these tests were run by rebooting
and running the test immediately after the box came up.  Repeating a
build.sh straight after a run had finished had no noticable impact on
the benchmark time.  It's interesting to note the differences in user
and system time when the wall-clock time remains similar in the sub-1
hour cases.

Right now that box is running with HT disabled, since I figured the
"extra" CPUs weren't worth it.

Simon.
--
Simon Burge                                   <simonb@wasabisystems.com>
NetBSD Development, Support and Service:   http://www.wasabisystems.com/