On Fri, Dec 01, 2017 at 12:58:47PM -0800, Randy Dunlap wrote: > Hi, > > I used "maxcpus=1" on a recent x86 boot (4.15-rc1) and got 4 CPUs (all of > them AFAICT). When I use "nr_cpus=1", I do get a hard limit of one CPU. > > > A few boot log excerpts: > > [ 0.000000] smpboot: Allowing 8 CPUs, 4 hotplug CPUs > ... > [ 0.030007] smp: Bringing up secondary CPUs ... > [ 0.030109] smp: Brought up 1 node, 1 CPU > [ 0.030181] smpboot: Max logical packages: 4 > [ 0.030255] smpboot: Total of 1 processors activated (4789.06 BogoMIPS) > > > Is systemd (or something else) later onlining the other CPUs? > > /sys/devices/system/cpu/online is 0-3 > /sys/devices/system/cpu/offline is 4-7
Check /lib/udev/rules.d/ for a rule that auto-onlines CPUs. This behavior is distribution specific.
