On Tuesday, September 28, 2010 6:24:32 pm Robert N. M. Watson wrote: > > On 28 Sep 2010, at 19:40, Sean Bruno wrote: > > >> If you go fully dynamic you should use mp_maxid + 1 rather than maxcpus. > > > > I assume that mp_maxid is the new kern.smp.maxcpus? Can you inject some > > history here so I can understand why one is "better" than the other? > > So, unlike maxcpus, mp_maxid is in theory susceptible to races in a brave new > world in which we support hotplug CPUs -- a brave new world we're not yet ready for, however. If you do use mp_maxid, be aware you need to add one to get the size of the array -- maxcpus is the number of CPUs that can be used, whereas mp_maxid is the highest CPU ID (counting from 0) that is used.
Hmm, I'm not sure that is true. My feeling on mp_maxid is that it is the largest supported CPUID. Platforms that support hotplug would need to set mp_maxid such that it has room for hotpluggable CPUs. You don't want to go reallocate the UMA datastructures for every zone when a CPU is hotplugged for example. -- John Baldwin _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
