Reduce timeslice for idle task based on wake time of sleeping tasks

RTC: 43738
Change-Id: I91c2bfe57bba04a02dd5169542de8e76e1654ae8
Reviewed-on: http://gfw160.austin.ibm.com:8080/gerrit/1387
Tested-by: Jenkins Server
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Reviewed-by: A. Patrick Williams III <iawillia@us.ibm.com>

1 files changed, 55 insertions, 30 deletions

diff --git a/src/include/kernel/timemgr.H b/src/include/kernel/timemgr.H
index 96950b928..3f6d658d7 100644
--- a/src/include/kernel/timemgr.H
+++ b/src/include/kernel/timemgr.H
@@ -1,25 +1,26 @@
-//  IBM_PROLOG_BEGIN_TAG
-//  This is an automatically generated prolog.
-//
-//  $Source: src/include/kernel/timemgr.H $
-//
-//  IBM CONFIDENTIAL
-//
-//  COPYRIGHT International Business Machines Corp. 2010 - 2011
-//
-//  p1
-//
-//  Object Code Only (OCO) source materials
-//  Licensed Internal Code Source Materials
-//  IBM HostBoot Licensed Internal Code
-//
-//  The source code for this program is not published or other-
-//  wise divested of its trade secrets, irrespective of what has
-//  been deposited with the U.S. Copyright Office.
-//
-//  Origin: 30
-//
-//  IBM_PROLOG_END
+/*  IBM_PROLOG_BEGIN_TAG
+ *  This is an automatically generated prolog.
+ *
+ *  $Source: src/include/kernel/timemgr.H $
+ *
+ *  IBM CONFIDENTIAL
+ *
+ *  COPYRIGHT International Business Machines Corp. 2010-2012
+ *
+ *  p1
+ *
+ *  Object Code Only (OCO) source materials
+ *  Licensed Internal Code Source Materials
+ *  IBM HostBoot Licensed Internal Code
+ *
+ *  The source code for this program is not published or other-
+ *  wise divested of its trade secrets, irrespective of what has
+ *  been deposited with the U.S. Copyright Office.
+ *
+ *  Origin: 30
+ *
+ *  IBM_PROLOG_END_TAG
+ */
 #ifndef __KERNEL_TIMEMGR_H
 #define __KERNEL_TIMEMGR_H
 
@@ -48,13 +49,22 @@ class TimeManager
 {
     public:
         enum
-            {
-                /** Number of time-slices to allow per second.
-                 *
-                 *  Context length becomes (1/TIMESLICE_PER_SECOND) sec.
-                 */
-                TIMESLICE_PER_SEC = 1000,
-            };
+        {
+            /** Number of time-slices to allow per second.
+             *
+             *  Context length becomes (1/TIMESLICE_PER_SECOND) sec.
+             */
+            TIMESLICE_PER_SEC = 1000,
+
+            /** Yield Threshold per timeslice
+             *
+             * @note At 512MHZ clock and TIMESLICE_PER_SEC = 1000,
+             *   Timeslice = 512000 ticks.
+             * If threshold/slice = 100 then threhold = 5120 ticks
+             * FYI, a Context switch ~ 476 ticks
+             */
+            YIELD_THRESHOLD_PER_SLICE = 100,    // 1%
+        };
 
             /** Initialize the time subsystem. */
         static void init();
@@ -68,6 +78,21 @@ class TimeManager
                 return iv_timebaseFreq / TIMESLICE_PER_SEC;
             };
 
+        /**
+         * Return the number of ticks for an idle time-slice
+         */
+        static uint64_t getIdleTimeSliceCount();
+
+        /**
+         * Perform a simple delay if the time is below the yield threshold.
+         *
+         * @param[in] sec, Delay time in seconds
+         * @param[in] nsec, Delay time in nano seconds
+         * @return false if the delay requires a task yield | true - The
+         * requested delay was performed by this routine.
+         */
+        static bool simpleDelay(uint64_t sec, uint64_t nsec);
+
             /** Returns the value of the processor timebase register. */
         static uint64_t getCurrentTimeBase()
             {
@@ -117,7 +142,7 @@ class TimeManager
         void _init_cpu(cpu_t* cpu);
         void _delayTask(task_t* t, uint64_t i_sec, uint64_t i_nsec);
         void _checkReleaseTasks(Scheduler* s);
-        inline delaylist_t* _get_delaylist();
+        static delaylist_t* _get_delaylist();
 
         /** Frequency of the timebase register in Hz. (ticks per second) */
         static uint64_t iv_timebaseFreq;