Date: Thu, 29 Jan 2015 22:51:22 -0500 From: Ryan Stone <rysto32@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r277900 - head/sys/x86/x86 Message-ID: <CAFMmRNxaartbZZ875F_YF01L7nQ%2BLKcd%2BUnD0RJdbJ=m0x5jbQ@mail.gmail.com> In-Reply-To: <8728880.CZu0UL854D@ralph.baldwin.cx> References: <201501292041.t0TKfhAJ029429@svn.freebsd.org> <8728880.CZu0UL854D@ralph.baldwin.cx>
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On Thu, Jan 29, 2015 at 3:45 PM, John Baldwin <jhb@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.
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