Hyperthreading or not?

Mendola Gaetano wrote:

Hi all,
we are going to move our production postgres box ( on Linux )
in a new machine, I'm wondering if I shall leave the Hyperthreading
feature on or disable it.
Anyone have experience on this?

Just FYI.

We turned Hyperthreading off for our production *dual* Xeon box. This is
mainly because we're on Linux 2.4.9 (+ Red Hat's patches for Advanced
Server). We've yet to see conclusive evidence that Linux 2.4.9 can take
dual Hyperthreaded processors into account, therefore we disabled it.

Please note emphasis on DUAL Hyperthreaded processors. If we have
processors A and B, Linux will see it as, say, A1, A2, B1, B2. We can't
tell if this version of Linux will not try to run two 100% CPU bound
processors on A1, and A2, while letting real processor B idle.

Didn't matter much in the end anyway, because postgresql handled our
load just fine on two real processors.

--
Linux homer 2.4.18-14 #1 Wed Sep 4 13:35:50 EDT 2002 i686 i686 i386
GNU/Linux
10:30am up 202 days, 1:35, 6 users, load average: 5.40, 5.14, 5.05

On Wed, 16 Jul 2003, Mendola Gaetano wrote:

Hi all,
we are going to move our production postgres box ( on Linux )
in a new machine, I'm wondering if I shall leave the Hyperthreading
feature on or disable it.

The newer kernels are hyper-threading aware. No idea how much faster that
might make things for a postgresql server though.

Anyone have experience on this?

Nope, but I will this fall.

PS: Is really faster postgresql compiled with Intel compiler ?

Note that since most people use gcc, any problems caused by the Intel
compiler might take more time to get fixed.

On 16 Jul 2003 at 9:07, scott.marlowe wrote:

PS: Is really faster postgresql compiled with Intel compiler ?

Note that since most people use gcc, any problems caused by the Intel
compiler might take more time to get fixed.

Last I heard was that gcc was pretty neck to neck with intel compiler with gcc
3.2.2 or later. Besides intel compiler yield performance gain on CPU intesive
applications such as mathematical calculations and as such.

While it would provide some performance benefit, I doubt how much and in how
many cases for a database app. like postgresql. It's not a CPU hog in the first
place, most of the times.

Bye
Shridhar

--
Bones: "The man's DEAD, Jim!"