Date: Fri, 24 Jun 2005 13:53:51 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Jens Schweikhardt <schweikh@schweikhardt.net> Cc: freebsd-current@FreeBSD.org Subject: Re: Timekeeping hosed by factor 3, high lapic[01] interrupt rates Message-ID: <200506241353.52383.jhb@FreeBSD.org> In-Reply-To: <20050624165002.GA860@schweikhardt.net> References: <20050516113420.GA786@schweikhardt.net> <200506231714.40891.jhb@FreeBSD.org> <20050624165002.GA860@schweikhardt.net>
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On Friday 24 June 2005 12:50 pm, Jens Schweikhardt wrote:
> On Thu, Jun 23, 2005 at 05:14:39PM -0400, John Baldwin wrote:
> ...
> # Ok. What timecounter does your UP kernel use, and does your UP kernel
> break # if you change the timecounter to i8254?
>
> The UP uses the TSC:
> $ sysctl -a|grep timec
> kern.timecounter.stepwarnings: 0
> kern.timecounter.nbinuptime: 136311
> kern.timecounter.nnanouptime: 0
> kern.timecounter.nmicrouptime: 664
> kern.timecounter.nbintime: 1273
> kern.timecounter.nnanotime: 36
> kern.timecounter.nmicrotime: 1237
> kern.timecounter.ngetbinuptime: 405
> kern.timecounter.ngetnanouptime: 29
> kern.timecounter.ngetmicrouptime: 2534
> kern.timecounter.ngetbintime: 0
> kern.timecounter.ngetnanotime: 0
> kern.timecounter.ngetmicrotime: 5
> kern.timecounter.nsetclock: 2
> kern.timecounter.hardware: TSC
> kern.timecounter.choice: TSC(800) i8254(0) dummy(-1000000)
> kern.timecounter.tick: 1
> kern.timecounter.smp_tsc: 0
>
> When I do
>
> $ sysctl kern.timecounter.hardware=i8254
>
> on the UP the time dilation by factor 3 starts and the lapic rate
> increases. So yes, that breaks the UP kernel.
Ok. Can you try this untested patch? It's mostly from phk and I haven't yet
tested it locally to make sure it doesn't break things:
--- //depot/vendor/freebsd/src/sys/i386/isa/clock.c 2005/05/14 09:10:26
+++ //depot/user/jhb/acpipci/i386/isa/clock.c 2005/06/24 17:30:30
@@ -136,6 +136,7 @@
static u_char timer2_state;
static unsigned i8254_get_timecount(struct timecounter *tc);
+static unsigned i8254_simple_get_timecount(struct timecounter *tc);
static void set_timer_freq(u_int freq, int intr_freq);
static struct timecounter i8254_timecounter = {
@@ -532,10 +533,15 @@
{
int new_timer0_max_count;
+ i8254_timecounter.tc_frequency = freq;
mtx_lock_spin(&clock_lock);
timer_freq = freq;
new_timer0_max_count = hardclock_max_count = TIMER_DIV(intr_freq);
- if (new_timer0_max_count != timer0_max_count) {
+ if (using_lapic_timer) {
+ outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
+ outb(TIMER_CNTR0, 0);
+ outb(TIMER_CNTR0, 0);
+ } else if (new_timer0_max_count != timer0_max_count) {
timer0_max_count = new_timer0_max_count;
outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
outb(TIMER_CNTR0, timer0_max_count & 0xff);
@@ -548,11 +554,7 @@
i8254_restore(void)
{
- mtx_lock_spin(&clock_lock);
- outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
- outb(TIMER_CNTR0, timer0_max_count & 0xff);
- outb(TIMER_CNTR0, timer0_max_count >> 8);
- mtx_unlock_spin(&clock_lock);
+ set_timer_freq(timer_freq, hz);
}
static void
@@ -627,7 +629,6 @@
}
set_timer_freq(timer_freq, hz);
- i8254_timecounter.tc_frequency = timer_freq;
tc_init(&i8254_timecounter);
init_TSC();
@@ -782,7 +783,8 @@
/*
* If we aren't using the local APIC timer to drive the kernel
* clocks, setup the interrupt handler for the 8254 timer 0 so
- * that it can drive hardclock().
+ * that it can drive hardclock(). Otherwise, change the 8254
+ * timecounter to user a simpler algorithm.
*/
if (!using_lapic_timer) {
intr_add_handler("clk", 0, (driver_intr_t *)clkintr, NULL,
@@ -791,6 +793,10 @@
if (i8254_intsrc != NULL)
i8254_pending =
i8254_intsrc->is_pic->pic_source_pending;
+ } else {
+ i8254_timecounter.tc_get_timecount =
+ i8254_simple_get_timecount;
+ set_timer_freq(timer_freq, hz);
}
/* Initialize RTC. */
@@ -858,10 +864,8 @@
*/
freq = timer_freq;
error = sysctl_handle_int(oidp, &freq, sizeof(freq), req);
- if (error == 0 && req->newptr != NULL) {
+ if (error == 0 && req->newptr != NULL)
set_timer_freq(freq, hz);
- i8254_timecounter.tc_frequency = freq;
- }
return (error);
}
@@ -869,6 +873,24 @@
0, sizeof(u_int), sysctl_machdep_i8254_freq, "IU", "");
static unsigned
+i8254_simple_get_timecount(struct timecounter *tc)
+{
+ u_int count;
+ u_int high, low;
+
+ mtx_lock_spin(&clock_lock);
+
+ /* Select timer0 and latch counter value. */
+ outb(TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
+
+ low = inb(TIMER_CNTR0);
+ high = inb(TIMER_CNTR0);
+ count = 0xffff - ((high << 8) | low);
+ mtx_unlock_spin(&clock_lock);
+ return (count);
+}
+
+static unsigned
i8254_get_timecount(struct timecounter *tc)
{
u_int count;
--
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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