Messages in this thread | | | Date | Mon, 11 Aug 2008 11:46:56 -0700 | From | Max Krasnyansky <> | Subject | Re: [PATCH] Resurect proper handling of maxcpus= kernel option |
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Ingo Molnar wrote: > * Max Krasnyansky <maxk@qualcomm.com> wrote: > >>> This will need some test time on 32-bit as that is where this >>> represents a material change. ( albeit what matters most is the >>> maxcpus=1 distinction - and for that nosmp can be used as well to >>> turn off multi-cpu support altogether. So we could do this in >>> v2.6.27 as well. ) >> So far we got a couple of reports that it works as expected on 32 >> (both laptop and server/desktop). > > Yes, but the usecase i'm worried about is when say maxcpus=1 was used to > _prevent_ an SMP bootup - because the system would not work otherwise. > > i guess we want to tickle those systems anyway as that case is not > supposed to happen (and it can always be totally disabled via nosmp or > noapic). > > So i'm not against your fix/change per se, i just wanted to highlight > that it has some impact on existing uses of maxcpus that is outside of > your cpu-hotplug usecase.
I see what you mean. I think it's fairly safe though since we do not actually do much for the cpus that are not going to be brought online. Mainly just setting cpu_*_map and initializing per cpu areas. If something is broken in there we'd probably want to fix that asap anyway. And like you said nosmp does the job too.
Max
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