On Fri, Mar 18, 2016 at 05:11:54AM +0100, Mike Galbraith wrote: > On Thu, 2016-03-17 at 10:52 +0100, Peter Zijlstra wrote: > > > Andreas; Borislav said to Cc you since you wrote all this. > > The issue is that Linux assumes: > > > > > nr_logical_cpus = nr_cores * nr_siblings > > It also seems to now assume that if SMT is possible, it's enabled. > > Below is my 8 socket DL980 G7, which has SMT turned off for RT testing, > booting NOPREEMPT master tuned for maximum bloat ala distro and getting > confused by me telling it (as always) nr_cpus=64. Bad juju ensues.
Ah, did you actually disable HT in the BIOS, or just skip the HT enumeration by saying nr_cpus=64 (knowing that all the siblings are last)? In any case, Thomas has a clue and I'm going to test, but 4 socket machine takes forever to boot, so might be a few minutes :/
