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[S390] boot cputime accounting

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Start the cpu time accounting very early to catch the cpu time spent
for the initial kernel setup. To make the output of /proc/uptime
match the sum of all cpu accounting values of the boot cpu reset
xtime and wall_to_monotonic to sane values based on the TOD clock.
The values set by timekeeping_init are off by up to a second.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2009-04-14 15:36:29 +02:00
parent b6112ccbff
commit ab96e798cb
4 changed files with 43 additions and 17 deletions
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36
arch/s390/kernel/time.c
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@@ -253,32 +253,52 @@ void update_vsyscall_tz(void)
*/
void __init time_init(void)
{
struct timespec ts;
unsigned long flags;
cycle_t now;
/* Reset time synchronization interfaces. */
etr_reset();
stp_reset();
/* set xtime */
tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &xtime);
set_normalized_timespec(&wall_to_monotonic,
-xtime.tv_sec, -xtime.tv_nsec);
/* request the clock comparator external interrupt */
if (register_early_external_interrupt(0x1004,
clock_comparator_interrupt,
&ext_int_info_cc) != 0)
panic("Couldn't request external interrupt 0x1004");
if (clocksource_register(&clocksource_tod) != 0)
panic("Could not register TOD clock source");
/* request the timing alert external interrupt */
if (register_early_external_interrupt(0x1406,
timing_alert_interrupt,
&ext_int_etr_cc) != 0)
panic("Couldn't request external interrupt 0x1406");
if (clocksource_register(&clocksource_tod) != 0)
panic("Could not register TOD clock source");
/*
* The TOD clock is an accurate clock. The xtime should be
* initialized in a way that the difference between TOD and
* xtime is reasonably small. Too bad that timekeeping_init
* sets xtime.tv_nsec to zero. In addition the clock source
* change from the jiffies clock source to the TOD clock
* source add another error of up to 1/HZ second. The same
* function sets wall_to_monotonic to a value that is too
* small for /proc/uptime to be accurate.
* Reset xtime and wall_to_monotonic to sane values.
*/
write_seqlock_irqsave(&xtime_lock, flags);
now = get_clock();
tod_to_timeval(now - TOD_UNIX_EPOCH, &xtime);
clocksource_tod.cycle_last = now;
clocksource_tod.raw_time = xtime;
tod_to_timeval(sched_clock_base_cc - TOD_UNIX_EPOCH, &ts);
set_normalized_timespec(&wall_to_monotonic, -ts.tv_sec, -ts.tv_nsec);
write_sequnlock_irqrestore(&xtime_lock, flags);
/* Enable TOD clock interrupts on the boot cpu. */
init_cpu_timer();
/* Enable cpu timer interrupts on the boot cpu. */
vtime_init();
}