Date: Fri, 30 Nov 2007 16:42:09 +0100 From: Kris Kennaway <kris@FreeBSD.org> To: Pete French <petefrench@ticketswitch.com> Cc: max@love2party.net, freebsd-stable@freebsd.org, kometen@gmail.com Subject: Re: Also seeing 2 x quad-core system slower that 2 x dual core Message-ID: <47502F51.3010007@FreeBSD.org> In-Reply-To: <E1Iy47z-0001f0-QX@dilbert.ticketswitch.com> References: <E1Iy47z-0001f0-QX@dilbert.ticketswitch.com>
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Pete French wrote: >> Yes, if the claim is that the hardware is absolutely identical apart >> from one having two quad-core CPUs instead of two dual-core, the next >> step is to disable half of the CPUs and confirm that the problem goes away. > > Just comming back to this today, will do a side by side compare of the dmesg > later to make sure that they *are* identical as claimed, but the idea of > disabling half the CPU's is an excellent one! > > Aha, brilliant idea! > >> Check dmesg for the APIC numbers corresponding to the CPUs you want to >> disable and add the corresponding entries to /boot/loader.conf, e.g.: > > You mean this bit? > > FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs > cpu0 (BSP): APIC ID: 0 > cpu1 (AP): APIC ID: 1 > cpu2 (AP): APIC ID: 2 > cpu3 (AP): APIC ID: 3 > cpu4 (AP): APIC ID: 4 > cpu5 (AP): APIC ID: 5 > cpu6 (AP): APIC ID: 6 > cpu7 (AP): APIC ID: 7 > >> hint.lapic.1.disable="1" >> hint.lapic.3.disable="1" >> hint.lapic.5.disable="1" >> hint.lapic.7.disable="1" > > gives me... > > hint.lapic.1.disable="1" > hint.lapic.3.disable="3" > hint.lapic.5.disable="5" > hint.lapic.7.disable="7" > > rebooting now to give it a try... Well, the "1" is a boolean so those values will probably also work, but the point was to disable apics 1,3,5 and 7 on the left hand side :) In your case those are also valid but sometimes they are other numbers. Kris
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