Messages in this thread | | | Date | Fri, 10 Feb 2006 11:05:21 +0100 | From | Heiko Carstens <> | Subject | Re: [PATCH] percpu data: only iterate over possible CPUs |
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> > > powerpc/ppc64, for instance, determines the number of possible cpus > > > from information exported by firmware (and I'm mystified as to why > > > other platforms don't do this). So it's typical to have a kernel an a > > > pSeries partition with NR_CPUS=128, but cpu_possible_map = 0xff. > > > > Simply because there is no such interface on s390. The only thing we know > > for sure is that if we are running under z/VM the user is free to > > configure up to 63 additional virtual cpus on the fly... > > x86-64 had the same problem, but we now require that you > boot with additional_cpus=... for how many you want. Default is 0 > (used to be half available CPUs but that lead to confusion)
So introducing the additional_cpus kernel parameter seems to be the way to go (for XEN probably too). Even though it seems to be a bit odd if the user specifies both maxcpus=... and additional_cpus=...
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