Date: Thu, 15 Jul 2010 18:57:09 +0200 (CEST) From: Oliver Fromme <olli@lurza.secnetix.de> To: freebsd-stable@FreeBSD.ORG, avg@icyb.net.ua, jkim@FreeBSD.ORG Subject: Re: 8.1-PRERELEASE: CPU packages not detected correctly Message-ID: <201007151657.o6FGv97V080710@lurza.secnetix.de> In-Reply-To: <4C3F0149.1070500@icyb.net.ua>
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Andriy Gapon wrote:
> on 15/07/2010 15:27 Oliver Fromme said the following:
> > Unfortunately, it didn't change. Kernel output during boot
> > is still the same; it displays 1 package x 8 cores.
>
> If you are sure that everything is done correctly (patch really applied, kernel
> really rebuilt and reinstalled, and reboot was to the new kernel), then perhaps
> jkim would be interested in this issue.
Yes, I'm sure, I even added some printf() so I can be sure
that the patched code is actually executed.
Here is what happens in sys/amd64/amd64/mp_machdep.c:
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)
This is the patch, it's against jkim's patched version:
@@ -265,7 +268,7 @@
else if (cpu_vendor_id == CPU_VENDOR_INTEL) {
if (cpu_high >= 0xb)
topo_probe_0xb();
- else if (cpu_high >= 0x4)
+ if (cpu_high >= 0x4 && cpu_cores == 0)
topo_probe_0x4();
}
if (cpu_cores == 0)
Best regards
Oliver
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