On 1/29/15 10:51 PM, Ryan Stone wrote: > On Thu, Jan 29, 2015 at 3:45 PM, John Baldwin <j...@freebsd.org> wrote: >> Also, note that we always use the TSC as the cpu ticker, even if it is not >> the >> timecounter. Thus, if C2+ is enabled on the systems, the kernel idle threads >> will have an artificially low runtime since their idle time is not properly >> accounted for. This does not affect any other threads as only the idle >> threads "run" while the CPU is in C2+ with the TSC effectively paused. The >> new default means that the idle threads will now have the proper runtime, >> however. > > However in a VM environment this means that runtimes for all threads > can be very wrong (regardless of whether we enter C2 or lower or not). > I have a coworker looking at using kvmclock in preference to TSC for > the cpu ticker when the kvmclock is available.
I think that is orthogonal to older Core 2 CPUs which the above mail was about. :) However, yes, that sounds sensible. You might want to talk to bryanv@. He has a branch in projects (projects/paravirt I think?) that provides a framework for hypervisor "drivers" that would be a good place to plug this into. -- John Baldwin _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
