Date: Tue, 8 Feb 2005 15:50:55 -0500 From: John Baldwin <jhb@FreeBSD.org> To: src-committers@FreeBSD.org Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/i386/i386 apic_vector.s local_apic.c mp_machdep.c src/sys/i386/include apicvar.h smp.h src/sys/i386/isa clock.c Message-ID: <200502081550.55445.jhb@FreeBSD.org> In-Reply-To: <200502082025.j18KP72E069507@repoman.freebsd.org> References: <200502082025.j18KP72E069507@repoman.freebsd.org>
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On Tuesday 08 February 2005 03:25 pm, John Baldwin wrote: > jhb 2005-02-08 20:25:07 UTC > > FreeBSD src repository > > Modified files: > sys/i386/i386 apic_vector.s local_apic.c mp_machdep.c > sys/i386/include apicvar.h smp.h > sys/i386/isa clock.c > Log: > Use the local APIC timer to drive the various kernel clocks on SMP > machines rather than forwarding interrupts from the clock devices around > using IPIs: - Add an IDT vector that pushes a clock frame and calls > lapic_handle_timer(). > - Add functions to program the local APIC timer including setting the > divisor, and setting up the timer to either down a periodic countdown > or one-shot countdown. > - Add a lapic_setup_clock() function that the BSP calls from > cpu_init_clocks() to setup the local APIC timer if it is going to be > used. The setup uses a one-shot countdown to calibrate the timer. We > then program the timer on each CPU to fire at a frequency of hz * 3. > stathz is defined as freq / 23 (hz * 3 / 23), and profhz is defined as > freq / 2 (hz * 3 / 2). This gives the clocks relatively prime divisors > while keeping a low LCM for the frequency of the clock interrupts. > Thanks to Peter Jeremy for suggesting this approach. > - Remove the hardclock and statclock forwarding code including the two > associated IPIs. The bitmap IPI handler has now effectively > degenerated to just IPI_AST. > - When the local APIC timer is used we don't turn the RTC on at all, but > we still enable interrupts on the ISA timer 0 (i8254) for timecounting > purposes. One caveat at the moment is that if you use ACPI throttle states (not Cx, but the hw.acpi.cpu.throttle_* (or whatever it's called now in a post cpufreq world) that the timer might operate at a different frequency. Currently there isn't a mechanism for notifying the system when the bus (not CPU clock) frequency changes, but once there is this will have to hook into it. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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