Messages in this thread | | | Date | Tue, 03 Jun 2008 16:47:49 -0700 | From | Max Krasnyanskiy <> | Subject | Re: Inquiry: Should we remove "isolcpus= kernel boot option? (may have realtime uses) |
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>> I would really appreciate some way to keep the kernel from using >> a CPU at all to do fault isolation. If possible not even booting it. > How does isolcpu= boot option helps in this case ? > I suppose the closes option is maxcpus=. We can probably add ignorecpus= or > something to handle your use case but it has nothing to do with isolcpus=.
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
This actually solves the case you're talking about (ie ignoring bad processors) instead of partially covering it with isolcpus=.
Dimitri, you can probably use that too. ie Boot the thing with most CPUs offline and then bring them online. That way you'll know for sure that no timers, works, hard-/soft-irqs, etc are running on them.
So I expect two ACKs for isolcpu= removal from both of you, in bold please :)
Max
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