Changeset f40139b in rtems for cpukit/score/cpu/no_cpu/rtems/score/cpu.h

Timestamp:

09/22/11 07:16:06 (12 years ago)

Author:

Sebastian Huber <sebastian.huber@…>

Branches:

4.11, 5, master

Children:

86c847c1

Parents:

82525a75

Message:

2011-09-22 Sebastian Huber <sebastian.huber@…>

PR 1914/cpukit

• rtems/score/cpu.h: Document CPU_TIMESTAMP_USE_STRUCT_TIMESPEC, CPU_TIMESTAMP_USE_INT64, and CPU_TIMESTAMP_USE_INT64_INLINE.

File:

• cpukit/score/cpu/no_cpu/rtems/score/cpu.h (modified) (1 diff)

cpukit/score/cpu/no_cpu/rtems/score/cpu.h

@@ -355 +355 @@
  */
 #define CPU_STRUCTURE_ALIGNMENT
+
+/**
+ *  @defgroup CPUTimestamp Processor Dependent Timestamp Support
+ *
+ *  This group assists in issues related to timestamp implementation.
+ *
+ *  The port must choose exactly one of the following defines:
+ *  - #define CPU_TIMESTAMP_USE_STRUCT_TIMESPEC TRUE
+ *  - #define CPU_TIMESTAMP_USE_INT64 TRUE
+ *  - #define CPU_TIMESTAMP_USE_INT64_INLINE TRUE
+ *
+ *  Performance of int64_t versus struct timespec
+ *  =============================================
+ *
+ *  On PowerPC/psim, inlined int64_t saves ~50 instructions on each
+ *    _Thread_Dispatch operation which results in a context switch.
+ *    This works out to be about 10% faster dispatches and 7.5% faster
+ *    blocking semaphore obtains.  The following numbers are in instructions
+ *    and from tm02 and tm26.
+ *
+ *                         timespec  int64  inlined int64
+ *    dispatch:              446      446      400
+ *    blocking sem obtain:   627      626      581
+ *
+ *  On SPARC/sis, inlined int64_t shows the same percentage gains.
+ *    The following numbers are in microseconds and from tm02 and tm26.
+ *
+ *                         timespec  int64  inlined int64
+ *    dispatch:               59       61       53
+ *    blocking sem obtain:    98      100       92
+ *
+ *  Inlining appears to have a tendency to increase the size of
+ *    some executables.
+ *  Not inlining reduces the execution improvement but does not seem to
+ *    be an improvement on the PowerPC and SPARC. The struct timespec
+ *    and the executables with int64 not inlined are about the same size.
+ */
+
+/**
+ *  @ingroup CPUTimestamp
+ *
+ *  Selects the timestamp implementation using struct timespec.
+ *
+ *  Port Specific Information:
+ *
+ *  XXX document implementation including references if appropriate
+ */
+#define CPU_TIMESTAMP_USE_STRUCT_TIMESPEC TRUE
+
+/**
+ *  @ingroup CPUTimestamp
+ *
+ *  Selects the timestamp implementation using int64_t and no inlined methods.
+ *
+ *  Port Specific Information:
+ *
+ *  XXX document implementation including references if appropriate
+ */
+#define CPU_TIMESTAMP_USE_INT64 TRUE
+
+/**
+ *  @ingroup CPUTimestamp
+ *
+ *  Selects the timestamp implementation using int64_t and inlined methods.
+ *
+ *  Port Specific Information:
+ *
+ *  XXX document implementation including references if appropriate
+ */
+#define CPU_TIMESTAMP_USE_INT64_INLINE TRUE
 
 /**