Date: Thu, 15 Jul 2010 14:32:24 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-stable@freebsd.org Cc: Oliver Fromme <olli@lurza.secnetix.de>, Andriy Gapon <avg@icyb.net.ua>, jkim@freebsd.org Subject: Re: 8.1-PRERELEASE: CPU packages not detected correctly Message-ID: <201007151432.25052.jhb@freebsd.org> In-Reply-To: <4C3F4BBB.30606@icyb.net.ua> References: <201007151657.o6FGv97V080710@lurza.secnetix.de> <4C3F4BBB.30606@icyb.net.ua>
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On Thursday, July 15, 2010 1:56:11 pm Andriy Gapon wrote: > on 15/07/2010 19:57 Oliver Fromme said the following: > > In topo_probe(), cpu_high is 0xd, so topo_probe_0xb() is > > called. But the cpuid 0xb instruction doesn't seem to > > return useful data: All values are zero already in the > > first level, so cpu_cores remains 0. > > > > Back in topo_probe(), there is a fallback if cpu_cores is > > stil 0: It assigns mp_ncpu to cpu_cores, so it gets 8 > > which is wrong. > > > > I patched topo_probe() so it calls topo_probe_0x4() after > > topo_probe_0xb() if cpu_cores is still 0. I think this > > is a better fallback procedure. With this patch, cpu_cores > > gets the value 4 which is the correct one, finally: > > > > FreeBSD/SMP: Multiprocessor System Detected: 8 CPUs > > FreeBSD/SMP: 2 package(s) x 4 core(s) > > Thank you for debugging this issue! > Not sure if this is the best patch that there can be, but its direction is > definitely correct. > As the Intel document says (translated to our x86 mp_machdep.c terms): > if cpu_high >= 0xb then we should execute cpuid_count(0xb, 0, p) and examine EBX > value (p[1]), only if it's non-zero should we proceed with topo_probe_0xb(), > otherwise we should fall back to topo_probe_0x4, etc. > > I think that your addition achieves this effect, perhaps just not as explicitly as > I would preferred. Maybe have topo_probe_0xb() explicitly call topo_probe_0x4() if EBX is 0? -- John Baldwin
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