From: Martin Schwidefsky <[email protected]>
The generic ktime_get function defined in kernel/hrtimer.c is suboptimial
for GENERIC_TIME=y:
0) | ktime_get() {
0) | ktime_get_ts() {
0) | getnstimeofday() {
0) | read_tod_clock() {
0) 0.601 us | }
0) 1.938 us | }
0) | set_normalized_timespec() {
0) 0.602 us | }
0) 4.375 us | }
0) 5.523 us | }
Overall there are two read_seqbegin/read_seqretry loops and a lot of
unnecessary struct timespec calculations. ktime_get returns a nano second
value which is the sum of xtime, wall_to_monotonic and the nano second
delta from the clock source.
ktime_get can be optimized for GENERIC_TIME=y. The new version only calls
clocksource_read:
0) | ktime_get() {
0) | read_tod_clock() {
0) 0.610 us | }
0) 1.977 us | }
It uses a single read_seqbegin/readseqretry loop and just adds everthing
to a nano second value.
ktime_get_ts is optimized in a similar fashion.
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: john stultz <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>
---
kernel/hrtimer.c | 4 ++
kernel/time/timekeeping.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 67 insertions(+)
diff -urpN linux-2.5/kernel/hrtimer.c linux-2.5-patched/kernel/hrtimer.c
--- linux-2.5/kernel/hrtimer.c 2009-07-03 10:46:07.000000000 +0200
+++ linux-2.5-patched/kernel/hrtimer.c 2009-07-03 10:46:23.000000000 +0200
@@ -46,6 +46,7 @@
#include <asm/uaccess.h>
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get - get the monotonic time in ktime_t format
*
@@ -60,6 +61,7 @@ ktime_t ktime_get(void)
return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get);
+#endif
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
@@ -104,6 +106,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base,
}
};
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get_ts - get the monotonic clock in timespec format
* @ts: pointer to timespec variable
@@ -128,6 +131,7 @@ void ktime_get_ts(struct timespec *ts)
ts->tv_nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
+#endif
/*
* Get the coarse grained time at the softirq based on xtime and
diff -urpN linux-2.5/kernel/time/timekeeping.c linux-2.5-patched/kernel/time/timekeeping.c
--- linux-2.5/kernel/time/timekeeping.c 2009-07-03 10:46:07.000000000 +0200
+++ linux-2.5-patched/kernel/time/timekeeping.c 2009-07-03 10:46:23.000000000 +0200
@@ -118,6 +118,69 @@ void getnstimeofday(struct timespec *ts)
EXPORT_SYMBOL(getnstimeofday);
+ktime_t ktime_get(void)
+{
+ cycle_t cycle_now, cycle_delta;
+ struct timespec time;
+ unsigned long seq;
+ s64 nsecs;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ time.tv_sec = xtime.tv_sec + wall_to_monotonic.tv_sec;
+ time.tv_nsec = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
+
+ /* read clocksource: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs = cyc2ns(clock, cycle_delta);
+
+ } while (read_seqretry(&xtime_lock, seq));
+ nsecs += time.tv_sec * 1000000000ULL + time.tv_nsec;
+ return (ktime_t) { .tv64 = nsecs };
+}
+EXPORT_SYMBOL_GPL(ktime_get);
+
+/**
+ * ktime_get_ts - get the monotonic clock in timespec format
+ * @ts: pointer to timespec variable
+ *
+ * The function calculates the monotonic clock from the realtime
+ * clock and the wall_to_monotonic offset and stores the result
+ * in normalized timespec format in the variable pointed to by @ts.
+ */
+void ktime_get_ts(struct timespec *ts)
+{
+ cycle_t cycle_now, cycle_delta;
+ struct timespec tomono;
+ unsigned long seq;
+ s64 nsecs;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ *ts = xtime;
+ tomono = wall_to_monotonic;
+
+ /* read clocksource: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs = cyc2ns(clock, cycle_delta);
+
+ } while (read_seqretry(&xtime_lock, seq));
+
+ set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
+ ts->tv_nsec + tomono.tv_nsec + nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get_ts);
+
/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
Martin Schwidefsky a ?crit :
> From: Martin Schwidefsky <[email protected]>
>
> The generic ktime_get function defined in kernel/hrtimer.c is suboptimial
> for GENERIC_TIME=y:
>
> 0) | ktime_get() {
> 0) | ktime_get_ts() {
> 0) | getnstimeofday() {
> 0) | read_tod_clock() {
> 0) 0.601 us | }
> 0) 1.938 us | }
> 0) | set_normalized_timespec() {
> 0) 0.602 us | }
> 0) 4.375 us | }
> 0) 5.523 us | }
>
> Overall there are two read_seqbegin/read_seqretry loops and a lot of
> unnecessary struct timespec calculations. ktime_get returns a nano second
> value which is the sum of xtime, wall_to_monotonic and the nano second
> delta from the clock source.
>
> ktime_get can be optimized for GENERIC_TIME=y. The new version only calls
> clocksource_read:
>
> 0) | ktime_get() {
> 0) | read_tod_clock() {
> 0) 0.610 us | }
> 0) 1.977 us | }
>
> It uses a single read_seqbegin/readseqretry loop and just adds everthing
> to a nano second value.
>
> ktime_get_ts is optimized in a similar fashion.
>
> Cc: Ingo Molnar <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: john stultz <[email protected]>
> Signed-off-by: Martin Schwidefsky <[email protected]>
> ---
> kernel/hrtimer.c | 4 ++
> kernel/time/timekeeping.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 67 insertions(+)
>
>
> diff -urpN linux-2.5/kernel/hrtimer.c linux-2.5-patched/kernel/hrtimer.c
> --- linux-2.5/kernel/hrtimer.c 2009-07-03 10:46:07.000000000 +0200
> +++ linux-2.5-patched/kernel/hrtimer.c 2009-07-03 10:46:23.000000000 +0200
> @@ -46,6 +46,7 @@
>
> #include <asm/uaccess.h>
>
> +#ifndef CONFIG_GENERIC_TIME
> /**
> * ktime_get - get the monotonic time in ktime_t format
> *
> @@ -60,6 +61,7 @@ ktime_t ktime_get(void)
> return timespec_to_ktime(now);
> }
> EXPORT_SYMBOL_GPL(ktime_get);
> +#endif
>
> /**
> * ktime_get_real - get the real (wall-) time in ktime_t format
> @@ -104,6 +106,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base,
> }
> };
>
> +#ifndef CONFIG_GENERIC_TIME
> /**
> * ktime_get_ts - get the monotonic clock in timespec format
> * @ts: pointer to timespec variable
> @@ -128,6 +131,7 @@ void ktime_get_ts(struct timespec *ts)
> ts->tv_nsec + tomono.tv_nsec);
> }
> EXPORT_SYMBOL_GPL(ktime_get_ts);
> +#endif
>
> /*
> * Get the coarse grained time at the softirq based on xtime and
> diff -urpN linux-2.5/kernel/time/timekeeping.c linux-2.5-patched/kernel/time/timekeeping.c
> --- linux-2.5/kernel/time/timekeeping.c 2009-07-03 10:46:07.000000000 +0200
> +++ linux-2.5-patched/kernel/time/timekeeping.c 2009-07-03 10:46:23.000000000 +0200
> @@ -118,6 +118,69 @@ void getnstimeofday(struct timespec *ts)
>
> EXPORT_SYMBOL(getnstimeofday);
>
> +ktime_t ktime_get(void)
> +{
> + cycle_t cycle_now, cycle_delta;
> + struct timespec time;
> + unsigned long seq;
> + s64 nsecs;
> +
> + do {
> + seq = read_seqbegin(&xtime_lock);
minor nit : read_seqbegin() returns an "unsigned int", not an "unsigned long"
But apparently, most callers store the value into an unsigned long... oh well...
On Mon, 06 Jul 2009 16:07:22 +0200
Eric Dumazet <[email protected]> wrote:
> > diff -urpN linux-2.5/kernel/time/timekeeping.c linux-2.5-patched/kernel/time/timekeeping.c
> > --- linux-2.5/kernel/time/timekeeping.c 2009-07-03 10:46:07.000000000 +0200
> > +++ linux-2.5-patched/kernel/time/timekeeping.c 2009-07-03 10:46:23.000000000 +0200
> > @@ -118,6 +118,69 @@ void getnstimeofday(struct timespec *ts)
> >
> > EXPORT_SYMBOL(getnstimeofday);
> >
> > +ktime_t ktime_get(void)
> > +{
> > + cycle_t cycle_now, cycle_delta;
> > + struct timespec time;
> > + unsigned long seq;
> > + s64 nsecs;
> > +
> > + do {
> > + seq = read_seqbegin(&xtime_lock);
>
> minor nit : read_seqbegin() returns an "unsigned int", not an "unsigned long"
Hmm, just cut-copy-pasted the seq-loop. Seems like a job for the janitor ..
But I will update my patch.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
On Mon, 2009-07-06 at 15:49 +0200, Martin Schwidefsky wrote:
> From: Martin Schwidefsky <[email protected]>
>
> The generic ktime_get function defined in kernel/hrtimer.c is suboptimial
> for GENERIC_TIME=y:
>
> 0) | ktime_get() {
> 0) | ktime_get_ts() {
> 0) | getnstimeofday() {
> 0) | read_tod_clock() {
> 0) 0.601 us | }
> 0) 1.938 us | }
> 0) | set_normalized_timespec() {
> 0) 0.602 us | }
> 0) 4.375 us | }
> 0) 5.523 us | }
>
> Overall there are two read_seqbegin/read_seqretry loops and a lot of
> unnecessary struct timespec calculations. ktime_get returns a nano second
> value which is the sum of xtime, wall_to_monotonic and the nano second
> delta from the clock source.
>
> ktime_get can be optimized for GENERIC_TIME=y. The new version only calls
> clocksource_read:
>
> 0) | ktime_get() {
> 0) | read_tod_clock() {
> 0) 0.610 us | }
> 0) 1.977 us | }
>
> It uses a single read_seqbegin/readseqretry loop and just adds everthing
> to a nano second value.
>
> ktime_get_ts is optimized in a similar fashion.
>
> Cc: Ingo Molnar <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: john stultz <[email protected]>
> Signed-off-by: Martin Schwidefsky <[email protected]>
Looks good to me.
Acked-by: John Stultz <[email protected]>
> ---
> kernel/hrtimer.c | 4 ++
> kernel/time/timekeeping.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 67 insertions(+)
>
>
> diff -urpN linux-2.5/kernel/hrtimer.c linux-2.5-patched/kernel/hrtimer.c
> --- linux-2.5/kernel/hrtimer.c 2009-07-03 10:46:07.000000000 +0200
> +++ linux-2.5-patched/kernel/hrtimer.c 2009-07-03 10:46:23.000000000 +0200
> @@ -46,6 +46,7 @@
>
> #include <asm/uaccess.h>
>
> +#ifndef CONFIG_GENERIC_TIME
> /**
> * ktime_get - get the monotonic time in ktime_t format
> *
> @@ -60,6 +61,7 @@ ktime_t ktime_get(void)
> return timespec_to_ktime(now);
> }
> EXPORT_SYMBOL_GPL(ktime_get);
> +#endif
>
> /**
> * ktime_get_real - get the real (wall-) time in ktime_t format
> @@ -104,6 +106,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base,
> }
> };
>
> +#ifndef CONFIG_GENERIC_TIME
> /**
> * ktime_get_ts - get the monotonic clock in timespec format
> * @ts: pointer to timespec variable
> @@ -128,6 +131,7 @@ void ktime_get_ts(struct timespec *ts)
> ts->tv_nsec + tomono.tv_nsec);
> }
> EXPORT_SYMBOL_GPL(ktime_get_ts);
> +#endif
>
> /*
> * Get the coarse grained time at the softirq based on xtime and
> diff -urpN linux-2.5/kernel/time/timekeeping.c linux-2.5-patched/kernel/time/timekeeping.c
> --- linux-2.5/kernel/time/timekeeping.c 2009-07-03 10:46:07.000000000 +0200
> +++ linux-2.5-patched/kernel/time/timekeeping.c 2009-07-03 10:46:23.000000000 +0200
> @@ -118,6 +118,69 @@ void getnstimeofday(struct timespec *ts)
>
> EXPORT_SYMBOL(getnstimeofday);
>
> +ktime_t ktime_get(void)
> +{
> + cycle_t cycle_now, cycle_delta;
> + struct timespec time;
> + unsigned long seq;
> + s64 nsecs;
> +
> + do {
> + seq = read_seqbegin(&xtime_lock);
> + time.tv_sec = xtime.tv_sec + wall_to_monotonic.tv_sec;
> + time.tv_nsec = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
> +
> + /* read clocksource: */
> + cycle_now = clocksource_read(clock);
> +
> + /* calculate the delta since the last update_wall_time: */
> + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
> +
> + /* convert to nanoseconds: */
> + nsecs = cyc2ns(clock, cycle_delta);
> +
> + } while (read_seqretry(&xtime_lock, seq));
> + nsecs += time.tv_sec * 1000000000ULL + time.tv_nsec;
> + return (ktime_t) { .tv64 = nsecs };
> +}
> +EXPORT_SYMBOL_GPL(ktime_get);
> +
> +/**
> + * ktime_get_ts - get the monotonic clock in timespec format
> + * @ts: pointer to timespec variable
> + *
> + * The function calculates the monotonic clock from the realtime
> + * clock and the wall_to_monotonic offset and stores the result
> + * in normalized timespec format in the variable pointed to by @ts.
> + */
> +void ktime_get_ts(struct timespec *ts)
> +{
> + cycle_t cycle_now, cycle_delta;
> + struct timespec tomono;
> + unsigned long seq;
> + s64 nsecs;
> +
> + do {
> + seq = read_seqbegin(&xtime_lock);
> + *ts = xtime;
> + tomono = wall_to_monotonic;
> +
> + /* read clocksource: */
> + cycle_now = clocksource_read(clock);
> +
> + /* calculate the delta since the last update_wall_time: */
> + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
> +
> + /* convert to nanoseconds: */
> + nsecs = cyc2ns(clock, cycle_delta);
> +
> + } while (read_seqretry(&xtime_lock, seq));
> +
> + set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
> + ts->tv_nsec + tomono.tv_nsec + nsecs);
> +}
> +EXPORT_SYMBOL_GPL(ktime_get_ts);
> +
> /**
> * do_gettimeofday - Returns the time of day in a timeval
> * @tv: pointer to the timeval to be set
>
>
On Mon, 6 Jul 2009, Martin Schwidefsky wrote:
> +ktime_t ktime_get(void)
> +{
> + cycle_t cycle_now, cycle_delta;
> + struct timespec time;
> + unsigned long seq;
> + s64 nsecs;
> +
> + do {
> + seq = read_seqbegin(&xtime_lock);
> + time.tv_sec = xtime.tv_sec + wall_to_monotonic.tv_sec;
> + time.tv_nsec = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
That's actually a violation of the timespec semantics. tv_nsec can end
up greater than (10^9 - 1). Please use separate sec and nsec variables.
secs = xtime.tv_sec + wall_to_monotonic.tv_sec;
nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
> + /* read clocksource: */
> + cycle_now = clocksource_read(clock);
> +
> + /* calculate the delta since the last update_wall_time: */
> + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
> +
> + /* convert to nanoseconds: */
> + nsecs = cyc2ns(clock, cycle_delta);
So that needs to be changed to:
nsecs += cyc2ns(clock, cycle_delta);
> +
> + } while (read_seqretry(&xtime_lock, seq));
> + nsecs += time.tv_sec * 1000000000ULL + time.tv_nsec;
> + return (ktime_t) { .tv64 = nsecs };
This will break all 32bit architectures which do not have
CONFIG_KTIME_SCALAR set.
With the above changes applied:
return ktime_add_ns(ktime_set(secs, 0), nsecs);
will do the trick. Might need some comments though :)
Thanks,
tglx
On Mon, 6 Jul 2009 22:31:39 +0200 (CEST)
Thomas Gleixner <[email protected]> wrote:
> On Mon, 6 Jul 2009, Martin Schwidefsky wrote:
> > +ktime_t ktime_get(void)
> > +{
> > + cycle_t cycle_now, cycle_delta;
> > + struct timespec time;
> > + unsigned long seq;
> > + s64 nsecs;
> > +
> > + do {
> > + seq = read_seqbegin(&xtime_lock);
> > + time.tv_sec = xtime.tv_sec + wall_to_monotonic.tv_sec;
> > + time.tv_nsec = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
>
> That's actually a violation of the timespec semantics. tv_nsec can end
> up greater than (10^9 - 1). Please use separate sec and nsec variables.
Well the tv_sec/tv_nsec fields of a timespec are long values. But its
no problem to switch to local variables.
> secs = xtime.tv_sec + wall_to_monotonic.tv_sec;
> nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
>
> > + /* read clocksource: */
> > + cycle_now = clocksource_read(clock);
> > +
> > + /* calculate the delta since the last update_wall_time: */
> > + cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
> > +
> > + /* convert to nanoseconds: */
> > + nsecs = cyc2ns(clock, cycle_delta);
>
> So that needs to be changed to:
>
> nsecs += cyc2ns(clock, cycle_delta);
Ok.
> > +
> > + } while (read_seqretry(&xtime_lock, seq));
> > + nsecs += time.tv_sec * 1000000000ULL + time.tv_nsec;
> > + return (ktime_t) { .tv64 = nsecs };
>
> This will break all 32bit architectures which do not have
> CONFIG_KTIME_SCALAR set.
Yep, that is a bug.
> With the above changes applied:
>
> return ktime_add_ns(ktime_set(secs, 0), nsecs);
>
> will do the trick. Might need some comments though :)
Ok, will update the patch. Thanks for the review.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
Martin,
On Tue, 7 Jul 2009, Martin Schwidefsky wrote:
> On Mon, 6 Jul 2009 22:31:39 +0200 (CEST)
> Thomas Gleixner <[email protected]> wrote:
>
> > On Mon, 6 Jul 2009, Martin Schwidefsky wrote:
> > > +ktime_t ktime_get(void)
> > > +{
> > > + cycle_t cycle_now, cycle_delta;
> > > + struct timespec time;
> > > + unsigned long seq;
> > > + s64 nsecs;
> > > +
> > > + do {
> > > + seq = read_seqbegin(&xtime_lock);
> > > + time.tv_sec = xtime.tv_sec + wall_to_monotonic.tv_sec;
> > > + time.tv_nsec = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
> >
> > That's actually a violation of the timespec semantics. tv_nsec can end
> > up greater than (10^9 - 1). Please use separate sec and nsec variables.
>
> Well the tv_sec/tv_nsec fields of a timespec are long values. But its
> no problem to switch to local variables.
Right. I'm not worried about an overflow of the variable. I was about
to suggest using timespec_to_ktime() to fix the !SCALAR problem when I
noticed that the timespec is possibly not normalized. Not using a
timespec makes the code more obvious I think.
Thanks,
tglx
On Tue, 7 Jul 2009 10:08:56 +0200 (CEST)
Thomas Gleixner <[email protected]> wrote:
> Martin,
>
> On Tue, 7 Jul 2009, Martin Schwidefsky wrote:
> > On Mon, 6 Jul 2009 22:31:39 +0200 (CEST)
> > Thomas Gleixner <[email protected]> wrote:
> >
> > > On Mon, 6 Jul 2009, Martin Schwidefsky wrote:
> > > > +ktime_t ktime_get(void)
> > > > +{
> > > > + cycle_t cycle_now, cycle_delta;
> > > > + struct timespec time;
> > > > + unsigned long seq;
> > > > + s64 nsecs;
> > > > +
> > > > + do {
> > > > + seq = read_seqbegin(&xtime_lock);
> > > > + time.tv_sec = xtime.tv_sec + wall_to_monotonic.tv_sec;
> > > > + time.tv_nsec = xtime.tv_nsec + wall_to_monotonic.tv_nsec;
> > >
> > > That's actually a violation of the timespec semantics. tv_nsec can end
> > > up greater than (10^9 - 1). Please use separate sec and nsec variables.
> >
> > Well the tv_sec/tv_nsec fields of a timespec are long values. But its
> > no problem to switch to local variables.
>
> Right. I'm not worried about an overflow of the variable. I was about
> to suggest using timespec_to_ktime() to fix the !SCALAR problem when I
> noticed that the timespec is possibly not normalized. Not using a
> timespec makes the code more obvious I think.
That makes sense. New patch:
--
Subject: [PATCH] optimized ktime_get[_ts] for GENERIC_TIME=y
From: Martin Schwidefsky <[email protected]>
The generic ktime_get function defined in kernel/hrtimer.c is suboptimial
for GENERIC_TIME=y:
0) | ktime_get() {
0) | ktime_get_ts() {
0) | getnstimeofday() {
0) | read_tod_clock() {
0) 0.601 us | }
0) 1.938 us | }
0) | set_normalized_timespec() {
0) 0.602 us | }
0) 4.375 us | }
0) 5.523 us | }
Overall there are two read_seqbegin/read_seqretry loops and a lot of
unnecessary struct timespec calculations. ktime_get returns a nano second
value which is the sum of xtime, wall_to_monotonic and the nano second
delta from the clock source.
ktime_get can be optimized for GENERIC_TIME=y. The new version only calls
clocksource_read:
0) | ktime_get() {
0) | read_tod_clock() {
0) 0.610 us | }
0) 1.977 us | }
It uses a single read_seqbegin/readseqretry loop and just adds everthing
to a nano second value.
ktime_get_ts is optimized in a similar fashion.
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Acked-by: john stultz <[email protected]>
Signed-off-by: Martin Schwidefsky <[email protected]>
---
kernel/hrtimer.c | 4 ++
kernel/time/timekeeping.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+)
diff -urpN linux-2.6/kernel/hrtimer.c linux-2.6-patched/kernel/hrtimer.c
--- linux-2.6/kernel/hrtimer.c 2009-07-07 11:24:29.000000000 +0200
+++ linux-2.6-patched/kernel/hrtimer.c 2009-07-07 11:24:37.000000000 +0200
@@ -48,6 +48,7 @@
#include <asm/uaccess.h>
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get - get the monotonic time in ktime_t format
*
@@ -62,6 +63,7 @@ ktime_t ktime_get(void)
return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get);
+#endif
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
@@ -106,6 +108,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base,
}
};
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get_ts - get the monotonic clock in timespec format
* @ts: pointer to timespec variable
@@ -130,6 +133,7 @@ void ktime_get_ts(struct timespec *ts)
ts->tv_nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
+#endif
/*
* Get the coarse grained time at the softirq based on xtime and
diff -urpN linux-2.6/kernel/time/timekeeping.c linux-2.6-patched/kernel/time/timekeeping.c
--- linux-2.6/kernel/time/timekeeping.c 2009-07-07 11:24:29.000000000 +0200
+++ linux-2.6-patched/kernel/time/timekeeping.c 2009-07-07 11:24:37.000000000 +0200
@@ -125,6 +125,71 @@ void getnstimeofday(struct timespec *ts)
EXPORT_SYMBOL(getnstimeofday);
+ktime_t ktime_get(void)
+{
+ cycle_t cycle_now, cycle_delta;
+ unsigned int seq;
+ s64 secs, nsecs;
+
+ do {
+ 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: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs += cyc2ns(clock, cycle_delta);
+
+ } while (read_seqretry(&xtime_lock, seq));
+ /*
+ * Use ktime_set/ktime_add_ns to create a proper ktime on
+ * 32-bit architectures without CONFIG_KTIME_SCALAR.
+ */
+ return ktime_add_ns(ktime_set(secs, 0), nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get);
+
+/**
+ * ktime_get_ts - get the monotonic clock in timespec format
+ * @ts: pointer to timespec variable
+ *
+ * The function calculates the monotonic clock from the realtime
+ * clock and the wall_to_monotonic offset and stores the result
+ * in normalized timespec format in the variable pointed to by @ts.
+ */
+void ktime_get_ts(struct timespec *ts)
+{
+ cycle_t cycle_now, cycle_delta;
+ struct timespec tomono;
+ unsigned int seq;
+ s64 nsecs;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ *ts = xtime;
+ tomono = wall_to_monotonic;
+
+ /* read clocksource: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs = cyc2ns(clock, cycle_delta);
+
+ } while (read_seqretry(&xtime_lock, seq));
+
+ set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
+ ts->tv_nsec + tomono.tv_nsec + nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get_ts);
+
/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
Commit-ID: 951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32
Gitweb: http://git.kernel.org/tip/951ed4d36b77ba9fe1ea08fc3c59d8bb6c9bda32
Author: Martin Schwidefsky <[email protected]>
AuthorDate: Tue, 7 Jul 2009 11:27:28 +0200
Committer: Thomas Gleixner <[email protected]>
CommitDate: Tue, 7 Jul 2009 12:47:33 +0200
timekeeping: optimized ktime_get[_ts] for GENERIC_TIME=y
The generic ktime_get function defined in kernel/hrtimer.c is suboptimial
for GENERIC_TIME=y:
0) | ktime_get() {
0) | ktime_get_ts() {
0) | getnstimeofday() {
0) | read_tod_clock() {
0) 0.601 us | }
0) 1.938 us | }
0) | set_normalized_timespec() {
0) 0.602 us | }
0) 4.375 us | }
0) 5.523 us | }
Overall there are two read_seqbegin/read_seqretry loops and a lot of
unnecessary struct timespec calculations. ktime_get returns a nano second
value which is the sum of xtime, wall_to_monotonic and the nano second
delta from the clock source.
ktime_get can be optimized for GENERIC_TIME=y. The new version only calls
clocksource_read:
0) | ktime_get() {
0) | read_tod_clock() {
0) 0.610 us | }
0) 1.977 us | }
It uses a single read_seqbegin/readseqretry loop and just adds everthing
to a nano second value.
ktime_get_ts is optimized in a similar fashion.
[ tglx: added WARN_ON(timekeeping_suspended) as in getnstimeofday() ]
Signed-off-by: Martin Schwidefsky <[email protected]>
Acked-by: john stultz <[email protected]>
LKML-Reference: <20090707112728.3005244d@skybase>
Signed-off-by: Thomas Gleixner <[email protected]>
---
kernel/hrtimer.c | 4 ++
kernel/time/timekeeping.c | 69 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 73 insertions(+), 0 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 9002958..829e066 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -48,6 +48,7 @@
#include <asm/uaccess.h>
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get - get the monotonic time in ktime_t format
*
@@ -62,6 +63,7 @@ ktime_t ktime_get(void)
return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get);
+#endif
/**
* ktime_get_real - get the real (wall-) time in ktime_t format
@@ -106,6 +108,7 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
}
};
+#ifndef CONFIG_GENERIC_TIME
/**
* ktime_get_ts - get the monotonic clock in timespec format
* @ts: pointer to timespec variable
@@ -130,6 +133,7 @@ void ktime_get_ts(struct timespec *ts)
ts->tv_nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);
+#endif
/*
* Get the coarse grained time at the softirq based on xtime and
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e8c77d9..7a24813 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -125,6 +125,75 @@ void getnstimeofday(struct timespec *ts)
EXPORT_SYMBOL(getnstimeofday);
+ktime_t ktime_get(void)
+{
+ cycle_t cycle_now, cycle_delta;
+ unsigned int seq;
+ s64 secs, nsecs;
+
+ WARN_ON(timekeeping_suspended);
+
+ do {
+ 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: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs += cyc2ns(clock, cycle_delta);
+
+ } while (read_seqretry(&xtime_lock, seq));
+ /*
+ * Use ktime_set/ktime_add_ns to create a proper ktime on
+ * 32-bit architectures without CONFIG_KTIME_SCALAR.
+ */
+ return ktime_add_ns(ktime_set(secs, 0), nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get);
+
+/**
+ * ktime_get_ts - get the monotonic clock in timespec format
+ * @ts: pointer to timespec variable
+ *
+ * The function calculates the monotonic clock from the realtime
+ * clock and the wall_to_monotonic offset and stores the result
+ * in normalized timespec format in the variable pointed to by @ts.
+ */
+void ktime_get_ts(struct timespec *ts)
+{
+ cycle_t cycle_now, cycle_delta;
+ struct timespec tomono;
+ unsigned int seq;
+ s64 nsecs;
+
+ WARN_ON(timekeeping_suspended);
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ *ts = xtime;
+ tomono = wall_to_monotonic;
+
+ /* read clocksource: */
+ cycle_now = clocksource_read(clock);
+
+ /* calculate the delta since the last update_wall_time: */
+ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
+
+ /* convert to nanoseconds: */
+ nsecs = cyc2ns(clock, cycle_delta);
+
+ } while (read_seqretry(&xtime_lock, seq));
+
+ set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
+ ts->tv_nsec + tomono.tv_nsec + nsecs);
+}
+EXPORT_SYMBOL_GPL(ktime_get_ts);
+
/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set