On Tue, Jan 16, 2024 at 09:07:17AM -0000, Stuart Henderson wrote:
| On 2024-01-16, Otto Moerbeek <o...@drijf.net> wrote:
| > On Tue, Jan 16, 2024 at 08:16:38AM +0100, Janne Johansson wrote:
| >
| >> Den tis 16 jan. 2024 kl 01:16 skrev Gustavo Rios <rios.gust...@gmail.com>:
| >> > Hi folks.
| >> > I have a simple question : How many cores does OBSD support ?
| >>
| >> amd64 says
| >>
| >> #define MAXCPUS 64 /* bitmask */
| >>
| >> but different arches have different limits.
| >
| > But do note that OpenBSD is not great in using many cores, expect it
| > to not scale in a linear way. It's best to make decisison on actual
| > measurments.
|
| It can vary a lot depending on what you're actually doing on the
| machine; pure computation will scale better than file access, for
| example. Keep an eye on "spin" in top(1) while testing. If you're seeing
| significant numbers for this, adding cores is not all that likely to
| help.
What Stuart said is very true - here's what I saw on my 16-core
machine with SMT enabled while encoding a Blu-Ray movie:
37135 weerd 2 20 1467M 1342M onproc/2 kqread 51.5H 2481.54% ghb
With SMT disabled (hw.smt=0), it got to well over 1500% CPU time, so
for this job it helped to enable SMT. Network traffic did not scale
that well when I last tried. So indeed, very much depends on your
workload.
Cheers,
Paul 'WEiRD' de Weerd
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