Messages in this thread | | | Subject | Re: [RFC][patch 11/12] timekeeper read clock helper functions | From | john stultz <> | Date | Thu, 30 Jul 2009 14:39:54 -0700 |
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On Wed, 2009-07-29 at 15:41 +0200, Martin Schwidefsky wrote: > plain text document attachment (timekeeper-helper.diff) > From: Martin Schwidefsky <schwidefsky@de.ibm.com> > > Add timekeeper_read_clock_ntp and timekeeper_read_clock_raw and use > them for getnstimeofday, ktime_get, ktime_get_ts and getrawmonotonic. > > Cc: Ingo Molnar <mingo@elte.hu> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: john stultz <johnstul@us.ibm.com> > Cc: Daniel Walker <dwalker@fifo99.com> > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> > --- > kernel/time/timekeeping.c | 91 +++++++++++++++++++--------------------------- > 1 file changed, 38 insertions(+), 53 deletions(-) > > Index: linux-2.6/kernel/time/timekeeping.c > =================================================================== > --- linux-2.6.orig/kernel/time/timekeeping.c > +++ linux-2.6/kernel/time/timekeeping.c > @@ -84,6 +84,40 @@ static void timekeeper_setup_internals(s > timekeeper.shift = clock->shift; > } > > +/* Timekeeper helper functions. */ > +static inline s64 timekeeper_read_clock_ntp(void) > +{ > + cycle_t cycle_now, cycle_delta; > + struct clocksource *clock; > + > + /* read clocksource: */ > + clock = timekeeper.clock; > + cycle_now = clock->read(clock); > +
I know it seems nice to have it here, but I think these helpers would be more reusable in other contexts if they took the cycle_now value as an argument. Also I'd drop the ntp bit, just to avoid confusing it with some ntp specific function. So:
timekeeping_get_ns(cycle_t now); timekeeping_get_ns_raw(cycle_t now);
That way in some situations we don't have to make two accesses to the hardware if we want to get both values at the same point.
Seem reasonable?
thanks -john
> + /* calculate the delta since the last update_wall_time: */ > + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > + > + /* return delta convert to nanoseconds using ntp adjusted mult. */ > + return clocksource_cyc2ns(cycle_delta, timekeeper.mult, > + timekeeper.shift); > +} > + > +static inline s64 timekeeper_read_clock_raw(void) > +{ > + cycle_t cycle_now, cycle_delta; > + struct clocksource *clock; > + > + /* read clocksource: */ > + clock = timekeeper.clock; > + cycle_now = clock->read(clock); > + > + /* calculate the delta since the last update_wall_time: */ > + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > + > + /* return delta convert to nanoseconds using ntp adjusted mult. */ > + return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift); > +} > + > /* > * This read-write spinlock protects us from races in SMP while > * playing with xtime. > @@ -172,8 +206,6 @@ static void timekeeping_forward_now(void > */ > void getnstimeofday(struct timespec *ts) > { > - cycle_t cycle_now, cycle_delta; > - struct clocksource *clock; > unsigned long seq; > s64 nsecs; > > @@ -183,17 +215,7 @@ void getnstimeofday(struct timespec *ts) > seq = read_seqbegin(&xtime_lock); > > *ts = xtime; > - > - /* read clocksource: */ > - clock = timekeeper.clock; > - cycle_now = clock->read(clock); > - > - /* calculate the delta since the last update_wall_time: */ > - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > - > - /* convert to nanoseconds: */ > - nsecs = clocksource_cyc2ns(cycle_delta, timekeeper.mult, > - timekeeper.shift); > + nsecs = timekeeper_read_clock_ntp(); > > /* If arch requires, add in gettimeoffset() */ > nsecs += arch_gettimeoffset(); > @@ -207,8 +229,6 @@ EXPORT_SYMBOL(getnstimeofday); > > ktime_t ktime_get(void) > { > - cycle_t cycle_now, cycle_delta; > - struct clocksource *clock; > unsigned int seq; > s64 secs, nsecs; > > @@ -218,17 +238,7 @@ ktime_t ktime_get(void) > seq = read_seqbegin(&xtime_lock); > secs = xtime.tv_sec + wall_to_monotonic.tv_sec; > nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec; > - > - /* read clocksource: */ > - clock = timekeeper.clock; > - cycle_now = clock->read(clock); > - > - /* calculate the delta since the last update_wall_time: */ > - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > - > - /* convert to nanoseconds: */ > - nsecs += clocksource_cyc2ns(cycle_delta, timekeeper.mult, > - timekeeper.shift); > + nsecs += timekeeper_read_clock_ntp(); > > } while (read_seqretry(&xtime_lock, seq)); > /* > @@ -249,8 +259,6 @@ EXPORT_SYMBOL_GPL(ktime_get); > */ > void ktime_get_ts(struct timespec *ts) > { > - cycle_t cycle_now, cycle_delta; > - struct clocksource *clock; > struct timespec tomono; > unsigned int seq; > s64 nsecs; > @@ -261,17 +269,7 @@ void ktime_get_ts(struct timespec *ts) > seq = read_seqbegin(&xtime_lock); > *ts = xtime; > tomono = wall_to_monotonic; > - > - /* read clocksource: */ > - clock = timekeeper.clock; > - cycle_now = clock->read(clock); > - > - /* calculate the delta since the last update_wall_time: */ > - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > - > - /* convert to nanoseconds: */ > - nsecs = clocksource_cyc2ns(cycle_delta, timekeeper.mult, > - timekeeper.shift); > + nsecs = timekeeper_read_clock_ntp(); > > } while (read_seqretry(&xtime_lock, seq)); > > @@ -433,23 +431,10 @@ void getrawmonotonic(struct timespec *ts > { > unsigned long seq; > s64 nsecs; > - cycle_t cycle_now, cycle_delta; > - struct clocksource *clock; > > do { > seq = read_seqbegin(&xtime_lock); > - > - /* read clocksource: */ > - clock = timekeeper.clock; > - cycle_now = clock->read(clock); > - > - /* calculate the delta since the last update_wall_time: */ > - cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; > - > - /* convert to nanoseconds: */ > - nsecs = clocksource_cyc2ns(cycle_delta, clock->mult, > - clock->shift); > - > + nsecs = timekeeper_read_clock_raw(); > *ts = raw_time; > > } while (read_seqretry(&xtime_lock, seq)); >
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