On 2018-07-25, Callum Davies <c...@crdavies.eu> wrote: > SMT was disabled in current about a month ago for speculative security > reasons. You can turn it back on using the sysctl hw.smt. Refer to the > commit message for revision 1.178 of src/sys/sys/sysctl.h for more > details and rationale.
That *may* be the reason, but the SMT "CPUs" aren't anything like individual CPU cores, various resources are shared. In many circumstances they won't add anything to performance. We have been doing package bulk builds with SMT disabled for a long time: it's significantly faster that way. hw.smt=1 may help at the expense of insufficient isolation between processes. But it might not. The thing causing slowness might be totally unrelated to this.
