[Info-vax] Disable hyper-threading from the DCL prompt

[Hein RMS van den Heuvel]

Several years back I did several HT experiments.

At that time I could not detect any performance difference between HYperthreading not having been enabled and having it enabled but with all co-threads de-activated (STOP /CPU).

As such I recommend to always boot with HT enabled to be able to activate without reboot when you feel like it.

Your mileage will vary, but from my experience for an underloaded systems ( < 50% cpu) HT does not help, but does not hurt either.
For overloaded systems ( > 90% cpu, frequent COM queue > 5 ) I find that HT allows one to stretch the performance enveloppe some. It gives the system a bit of elasticity if you like. It softens the 'knee' and you can expect more aggregate throughput, with some response time degradation of course.

fwiw,
Hein