Messages in this thread Patch in this message | | | Date | Fri, 8 Jun 2007 22:08:12 -0500 | Subject | [PATCH] [RFC] wrong cpus started | From | Mark Rustad <> |
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I have noticed that recent kernels, 2.6.16 through at least 2.6.19, hyperthreading can no longer be effectively disabled by using maxcpus. This means that anyone that was using maxcpus to disable hyperthreading when running Linux will no longer be using all of their physical cpus.
The following patch restores the earlier behavior, but I am fairly sure that some CPU hotplug environments would not want this change. I can imagine making the two lines moved in the patch below to instead be conditional on CONFIG_HOTPLUG_CPU and !CONFIG_HOTPLUG_CPU respectively. Can someone more familiar with hotplug CPU come up with a better fix?
--- a/arch/i386/kernel/mpparse.c 2006-11-29 15:57:37.000000000 -0600 +++ b/arch/i386/kernel/mpparse.c 2007-06-06 16:41:06.635814335 -0500 @@ -180,9 +180,6 @@ static void __devinit MP_processor_info } apic_version[m->mpc_apicid] = ver; - phys_cpu = apicid_to_cpu_present(apicid); - physids_or(phys_cpu_present_map, phys_cpu_present_map, phys_cpu); - if (num_processors >= NR_CPUS) { printk(KERN_WARNING "WARNING: NR_CPUS limit of %i reached." " Processor ignored.\n", NR_CPUS); @@ -195,6 +192,9 @@ static void __devinit MP_processor_info return; } + phys_cpu = apicid_to_cpu_present(apicid); + physids_or(phys_cpu_present_map, phys_cpu_present_map, phys_cpu); + cpu_set(num_processors, cpu_possible_map); num_processors++; -- Mark Rustad, mrustad@gmail.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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