Date: Mon, 25 Feb 2008 22:37:39 +1100 From: Tigger <tigger@lvlworld.com> To: freebsd-questions@freebsd.org Subject: Re: Dual core CPU's, but only 2 CPU's in-use? Message-ID: <20080225223739.723d9e14@piglet> In-Reply-To: <47C298B5.7040907@FreeBSD.org> References: <20080224110010.GA4447@edward.lilypie.com> <47C1590F.3020605@bsdforen.de> <20080224230744.50539c03@piglet> <47C18665.9050600@FreeBSD.org> <20080225210134.2d0e2908@piglet> <47C298B5.7040907@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Mon, 25 Feb 2008 11:30:13 +0100 Kris Kennaway <kris@FreeBSD.org> wrote: > Tigger wrote: > > On Sun, 24 Feb 2008 15:59:49 +0100 > > Kris Kennaway <kris@FreeBSD.org> wrote: > > > >> Tigger wrote: > >>> On Sun, 24 Feb 2008 12:46:23 +0100 > >>> Dominic Fandrey <kamikaze@bsdforen.de> wrote: > >>> > >>>> Tigger wrote: > >>>>> Hello. I have a Xeon system with 2 CPU's installed (dual-cores). > >>>>> Under FreeBSD 6.2, a systat reported 4 CPUs in use and so did > >>>>> dmesg. > >>>>> > >>>>> Under FreeBSD 6.3, dmesg is reporting the 4 CPUs, but systat is > >>>>> only reporting 2 CPUs (CPU 0 and CPU 2). > >>>>> > >>>>> How do I enabled the second cores on the CPU's or are they > >>>>> really running but systat is not reporting the CPU load across > >>>>> the cores? > >>>> You can run 'top -S' to check how many idle processes exist. If > >>>> there are four, everything is fine. > >>>> > >>> > >>> Sadly, no luck. Only cpu0 and cpu2 are reported: > >>> > >>> PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU > >>> COMMAND 11 root 1 171 52 0K 8K CPU2 2 143:43 > >>> 92.38% idle: cpu2 13 root 1 171 52 0K 8K RUN 0 > >>> 142:33 92.04% idle: cpu0 > >> Are your CPUs really dual-core, or single core + hyperthreaded? > >> > >> Kris > >> > > > > Thank you! Your email sent me off to do what I should have done > > first - some research. I assumed (wrongly) that 'Logical CPUs per > > core: 2' meant 'Dual Core', and when I saw the following: > > > > FreeBSD/SMP: Multiprocessor System Detected: 4 CPUs > > cpu0 (BSP): APIC ID: 0 > > cpu1 (AP): APIC ID: 1 > > cpu2 (AP): APIC ID: 6 > > cpu3 (AP): APIC ID: 7 > > > > I also thought 'Dual Core', however this is not the case. The CPU's > > are single core with Hyper Threading Tech. > > > > But this research has also lead to some confusion. Its clear there > > are 2 CPU with 2 Logical cores each, but only 2 cores are in use - > > why? > > > > Also, the 'man (4) smp' talks about (possible) performance issues > > with Hyper Threading enabled - does this mean I should set > > 'machdep.hlt_logical_cpus 1' (it is currently set to 0) - or > > because the Logical Cores are not being used I can forget about > > this? > > hyperthreading is not enabled by default on 6.x. See the security > advisory for discussion and how to enable it. > > Kris > The only security advisory I could find was for 5.x and contained info on how to disable, not enable. http://security.freebsd.org/advisories/FreeBSD-SA-05:09.htt.asc Also, 'machdep.hlt_logical_cpus' is already set to 0 (I'm assuming the 'hlt' means 'halt' in the sysctl switch). -Tig
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20080225223739.723d9e14>