On May 19, 2:32 am, David Woolley <[EMAIL PROTECTED]> wrote: > > HLT instructions are a complete red herring here. They've been available > for over 35 years, to my personal knowledge, and probably a lot more > than that. No mainstream Linux, and probably no Linux has not used > them.
Quite the contrary. Linux has been using HLT for over a decade now ans has always sported better power efficiency than Windows until it started to do so too with Windows 2000. > HLT is special in power management terms in that it doesn't require > heuristics on anything better than MSDOS, for any application that is at > all multi-tasking friendly. Mind you, HLT is merely the first line of defense in power management. HLT makes the CPU enter C1-state, but then the OS guides it when to enter the deeper power-saving C2 and C3 states. > But you've already told us that you get a 90% power saving before you go > to the deep state. In my view, a server that is running at a > sufficiently low CPU load that going deeper that HLT is useful is badly > over-dimensioned. Would you deal with an ideal world or with what is out there? > > the duty cycle resulting from the heuristics used by the hardware or > > the OS to decide when to place the CPU in a deep C-state. > > [A] I suspect it is actually single figure nano-seconds on modern machines. No, it's not. And I don't say it out of a vague suspicion, but out of knowledge gained when designing the algorithms at AMD, later used by both Windows and Linux. HTH _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
