Date: Thu, 14 Sep 2006 14:43:24 +0200 From: Ivan Voras <ivoras@fer.hr> To: freebsd-stable@freebsd.org Subject: Re: FreeBSD does not use all cpus on top show. Message-ID: <eebiq0$ea5$1@sea.gmane.org> In-Reply-To: <4508DC51.4060300@gddsn.org.cn> References: <4508DC51.4060300@gddsn.org.cn>
next in thread | previous in thread | raw e-mail | index | archive | help
Huang wen hui wrote: > hi, > I have HP Server install FreeBSD 6.1R/amd64 with 2CPUs ,2 logical CPUs > per core. > On top show, It should show 4 cpus, but I never see 1 and 3 cpu on show. > Does anything I miss? This is a simplified version of things, but it will help you: CPUs 0 and 2 are "real" CPUs, while 1 and 3 are additional hyperthreaded "counterparts" of those. Since hyperthreading is disabled in FreeBSD by default (because it generally doesn't help performance and has a sort-of security hole in the hardware itself), processes are never scheduled to run on CPUs 1 and 3. You can either disable hyperthreading in BIOS, so you'll have only CPUs 0 and 1, or enable hyperthreading in FreeBSD with machdep.hyperthreading_allowed=1 sysctl, which will enable you to use all 4 logical CPUs.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?eebiq0$ea5$1>