[rtems commit] score: Fix performance issue for 64-bit timestamps
Sebastian Huber
sebh at rtems.org
Thu Jun 14 12:17:33 UTC 2012
Module: rtems
Branch: master
Commit: c34bb0dcfa8ba1294cd5182349e1ddbe34f81bf4
Changeset: http://git.rtems.org/rtems/commit/?id=c34bb0dcfa8ba1294cd5182349e1ddbe34f81bf4
Author: Sebastian Huber <sebastian.huber at embedded-brains.de>
Date: Wed Jun 13 11:39:43 2012 +0200
score: Fix performance issue for 64-bit timestamps
The 64-bit timestamps were introduced to simplify the timestamp
calculations. This works well since nearly all operations are
additions. The previous _TOD_Tickle_ticks() implementation had a
serious performance regression in case of 64-bit timestamps due to the
usage of two 64-bit divisions which are quite expensive on some
architectures.
A new field seconds_trigger in TOD_Control is introduced to trigger the
_Watchdog_Tickle_seconds() in _TOD_Tickle_ticks(). This avoids the
64-bit divisions completely and only 32-bit additions are used.
---
cpukit/score/include/rtems/score/timestamp.h | 25 --------------------
cpukit/score/include/rtems/score/timestamp64.h | 30 ------------------------
cpukit/score/include/rtems/score/tod.h | 9 +++++++
cpukit/score/src/coretodset.c | 2 +
cpukit/score/src/coretodtickle.c | 18 ++++++++-----
5 files changed, 22 insertions(+), 62 deletions(-)
diff --git a/cpukit/score/include/rtems/score/timestamp.h b/cpukit/score/include/rtems/score/timestamp.h
index b860909..83948b4 100644
--- a/cpukit/score/include/rtems/score/timestamp.h
+++ b/cpukit/score/include/rtems/score/timestamp.h
@@ -194,31 +194,6 @@ extern "C" {
#endif
/**
- * @brief Add to a Timestamp (At Clock Tick)
- *
- * This routine adds two timestamps. The second argument is added
- * to the first.
- *
- * @node This routine places a special requirement on the addition
- * operation. It must return the number of units that the
- * seconds field changed as the result of the addition. Since this
- * operation is ONLY used as part of processing a clock tick,
- * it is generally safe to assume that only one second changed.
- *
- * @param[in] _time points to the base time to be added to
- * @param[in] _add points to the timestamp to add to the first argument
- *
- * @return This method returns the number of seconds @a time increased by.
- */
-#if CPU_TIMESTAMP_USE_STRUCT_TIMESPEC == TRUE
- #define _Timestamp_Add_to_at_tick( _time, _add ) \
- _Timespec_Add_to( _time, _add )
-#else
- #define _Timestamp_Add_to_at_tick( _time, _add ) \
- _Timestamp64_Add_to_at_tick( _time, _add )
-#endif
-
-/**
* @brief Convert Timestamp to Number of Ticks
*
* This routine convert the @a time timestamp to the corresponding number
diff --git a/cpukit/score/include/rtems/score/timestamp64.h b/cpukit/score/include/rtems/score/timestamp64.h
index 08d3ac7..1c1ea2c 100644
--- a/cpukit/score/include/rtems/score/timestamp64.h
+++ b/cpukit/score/include/rtems/score/timestamp64.h
@@ -209,36 +209,6 @@ static inline void _Timestamp64_implementation_Add_to(
#endif
/**
- * @brief Add to a Timestamp (At Clock Tick)
- *
- * This routine adds two timestamps. The second argument is added
- * to the first.
- *
- * @node This routine places a special requirement on the addition
- * operation. It must return the number of units that the
- * seconds field changed as the result of the addition. Since this
- * operation is ONLY used as part of processing a clock tick,
- * it is generally safe to assume that only one second changed.
- *
- * @param[in] _time points to the base time to be added to
- * @param[in] _add points to the timestamp to add to the first argument
- *
- * @return This method returns the number of seconds @a time increased by.
- */
-static inline uint32_t _Timestamp64_Add_to_at_tick(
- Timestamp64_Control *_time,
- const Timestamp64_Control *_add
-)
-{
- Timestamp64_Control _start = *_time / 1000000000L;
- *_time += *_add;
- if ( ((*_time) / 1000000000L) != _start ) {
- return 1;
- }
- return 0;
-}
-
-/**
* @brief Convert Timestamp to Number of Ticks
*
* This routine convert the @a time timestamp to the corresponding number
diff --git a/cpukit/score/include/rtems/score/tod.h b/cpukit/score/include/rtems/score/tod.h
index 06cc900..cfb0fe7 100644
--- a/cpukit/score/include/rtems/score/tod.h
+++ b/cpukit/score/include/rtems/score/tod.h
@@ -137,6 +137,15 @@ typedef struct {
Timestamp_Control uptime;
/**
+ * @brief Time of day seconds trigger.
+ *
+ * This value specifies the nanoseconds since the last time of day second.
+ * It is updated and evaluated in _TOD_Tickle_ticks(). It is set in
+ * _TOD_Set_with_timestamp().
+ */
+ uint32_t seconds_trigger;
+
+ /**
* @brief Indicates if the time of day is set.
*
* This is true if the application has set the current
diff --git a/cpukit/score/src/coretodset.c b/cpukit/score/src/coretodset.c
index 9708ef9..8b0928a 100644
--- a/cpukit/score/src/coretodset.c
+++ b/cpukit/score/src/coretodset.c
@@ -25,6 +25,7 @@ void _TOD_Set_with_timestamp(
const Timestamp_Control *tod
)
{
+ uint32_t nanoseconds = _Timestamp_Get_nanoseconds( tod );
Watchdog_Interval seconds_next = _Timestamp_Get_seconds( tod );
Watchdog_Interval seconds_now;
@@ -39,6 +40,7 @@ void _TOD_Set_with_timestamp(
_Watchdog_Adjust_seconds( WATCHDOG_FORWARD, seconds_next - seconds_now );
_TOD.now = *tod;
+ _TOD.seconds_trigger = nanoseconds;
_TOD.is_set = true;
_TOD_Activate();
diff --git a/cpukit/score/src/coretodtickle.c b/cpukit/score/src/coretodtickle.c
index fbf67fd..d0412f8 100644
--- a/cpukit/score/src/coretodtickle.c
+++ b/cpukit/score/src/coretodtickle.c
@@ -35,23 +35,27 @@
void _TOD_Tickle_ticks( void )
{
Timestamp_Control tick;
- uint32_t seconds;
+ uint32_t nanoseconds_per_tick;
+
+ nanoseconds_per_tick = rtems_configuration_get_nanoseconds_per_tick();
/* Convert the tick quantum to a timestamp */
- _Timestamp_Set( &tick, 0, rtems_configuration_get_nanoseconds_per_tick() );
+ _Timestamp_Set( &tick, 0, nanoseconds_per_tick );
/* Update the counter of ticks since boot */
_Watchdog_Ticks_since_boot += 1;
- /* Update the timespec format uptime */
+ /* Update the uptime */
_Timestamp_Add_to( &_TOD.uptime, &tick );
/* we do not care how much the uptime changed */
- /* Update the timespec format TOD */
- seconds = _Timestamp_Add_to_at_tick( &_TOD.now, &tick );
- while ( seconds ) {
+ /* Update the current TOD */
+ _Timestamp_Add_to( &_TOD.now, &tick );
+
+ _TOD.seconds_trigger += nanoseconds_per_tick;
+ if ( _TOD.seconds_trigger >= 1000000000UL ) {
+ _TOD.seconds_trigger -= 1000000000UL;
_Watchdog_Tickle_seconds();
- seconds--;
}
}
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