Date: Mon, 21 Nov 2005 12:48:45 -0500 From: <myfreebsd@cox.net> To: "Axel S. Gruner" <liste@encephalon.de> Cc: Axel.Gruner@suedfactoring.de, freebsd-questions@freebsd.org Subject: Re: Re: Load at 1.00 on SMP machine Message-ID: <20051121174858.PIYB29285.eastrmmtao03.cox.net@[172.18.52.8]>
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Have you tried it as follows: 1. Compile kernel with SMP and APIC included 2. Set machdep.hlt_logical_cpus=0 in loader.conf or sysctl.conf (0 not 1) 3. Set machdep.hyperthreading_allowed=1 in loader.conf See if that helps. If not, remove machdep.hyperthreading or set it to 0. From my understanding that should disable HTT >From FreeBSD 6.0 RelNotes: Because of an information disclosure vulnerability on processors using Hyper-Threading Technology (HTT), the machdep.hyperthreading_allowed sysctl variable has been added. It defaults to 1 (HTT enabled) on FreeBSD CURRENT, and 0 (HTT disabled) on the 4-STABLE and 5-STABLE development branches and supported security fix branches. More information can be found in security advisory FreeBSD-SA-05:09.htt. [MERGED] I think machdep.hlt_logical_cpus does not deactivate the other cpu it just keeps the OS from directing data to it hence the 1.00 load on your remaining cpu. David > > From: "Axel S. Gruner" <liste@encephalon.de> > Date: 2005/11/21 Mon PM 12:25:59 EST > To: <myfreebsd@cox.net> <myfreebsd@cox.net> > CC: <Axel.Gruner@suedfactoring.de>, freebsd-questions@freebsd.org > Subject: Re: Load at 1.00 on SMP machine > > Hi, > > Am 21.11.2005 um 16:17 schrieb <myfreebsd@cox.net> <myfreebsd@cox.net>: > > >> i got a Problem on my dual XEON 3.06 GhZ machine, 2GB of >RAM, > >> FreeBSD > >> 5.4-STABLE. > >> I got "option SMP" in the kernel config and > >> >"machdep.hlt_logical_cpus=1" in > >> /boot/loader.conf. > >> There are just 20 processes running (typical ones like >getty and > >> stuff) and > >> the load of this machine is at 1.xx. There is no bgfsck and >other > >> stuff. > > > >> So, i built a new kernel without "option SMP", rebooted, >and the > >> load was > >> at 0.0x. But only one CPU was used (detected). > > > >> So, what could bei the Problem? > >> Well, the machine shows me 4 CPUs, HTT is not enabled via >/boot/ > >> loader.conf > >> and "machdep.hyperthreading_allowed". So, how to disable >HTT? > >> Maybe this is > >> the problem of the high load? > > > > Why are you setting machdep.hlt_logical_cpus=1? My understanding, > > this would turn off one of the cpus. It should be set to 0 to have > > both cpus going. Also it is set in sysctl.conf not loader.conf, at > > least, that is how I have it. > > Both CPUs are working. Also, works with machdep in loader.conf. > Thats not the problem. > > > I am also curious how machdep.hyperthreading_allowed works. I run 6 > > so I believe it is turned on by default. Is this correct? Also if > > it is a solo cpu with HTT, do you need option SMP and > > machdep.hlt_logical_cpus=0 set or not with > > machdep.hyperthreading_allowed on? > > I do not know. I just want turn off HTT, but stay with SMP. So i want > my two phyiscal CPUs working, but not the logical (HTT) one. > This is because is think maybe the load of 1.0x comes from turning on > HTT. Well, if i do not use SMP in the kernel, the load is fine, but > there is just one of the physical CPUs working. > >
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