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SubjectRe: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses)
Ingo Oeser wrote:
> Hi Max,
>
> On Wednesday 04 June 2008, Max Krasnyanskiy wrote:
>> btw Ingo, I just realized that maxcpu= option is exactly what you need.
>> Here is how you can use it.
>> Boot your system with maxcpus=1. That way the kernel will only bring up
>> processor 0. I'm assuming cpu0 is "good" otherwise your system is totally
>> busted :). Other cpus will stay off-line and will not be initialized.
>> Then once the system boots you can selectively bring "good" processors online
>> by doing
>> echo 1 > /sys/devices/system/cpu/cpuN/online
>>
>
> I just tested it on the Ubuntu Hardy standard kernel on an AMD DualCore.
> The /sys/devices/system/cpu/cpu1 entry doesn't show up.
>
> I can send you the dmesg/config in private, if you want.
>
> Did you test your suggestion?
No, I just give random suggestions without verifying them first ;-).
Of course I tried it. Sounds like your Ubuntu kernel does not have "CPU
hotplug / suspend on SMP" enabled. I thought that all distributions enable it
by default these days.

Max


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