git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@158 35acf78f-673a-0410-8e92-d51de3d6d3f4

readme.txt

@@ -52,9 +52,11 @@ AVR-AT90CANx-GCC       - Port on AVR AT90CAN128, not complete yet.
   for the same problem.
 - Fixed a bug in the round robin scheduling mode, see the bug tracker for
   details and a fix for previous versions.
-- More performance improvements to the scheduler, see the remarks into the
-  chSchWakeupS() function source. This change makes the ready list insertion
-  time in many cases constant (not influenced by the number of ready threads).
+- More performance improvements to the scheduler. The ready list insertion
+  sequence is now reversed, it is scanned starting from the highest priority
+  end. This has an important side effect into the chSchWakeupS() that makes
+  most of the ready list insertions happen in constant time (extraction is
+  done always in constant time).
   The worst case is always proportional to the number of threads in the ready
   list but the normal case is much more often constant than linear. See the
   new benchmarks added to the test suite.

src/chschd.c

@@ -35,7 +35,7 @@ ReadyList rlist;
 void chSchInit(void) {
 
   fifo_init(&rlist.r_queue);
-//  rlist.r_prio = ABSPRIO;
+  rlist.r_prio = NOPRIO;
   rlist.r_preempt = CH_TIME_QUANTUM;
 #ifdef CH_USE_SYSTEMTIME
   rlist.r_stime = 0;
@@ -58,10 +58,17 @@ INLINE void chSchReadyI(Thread *tp, t_msg msg) {
 #else
 void chSchReadyI(Thread *tp, t_msg msg) {
 #endif
+  Thread *cp = rlist.r_queue.p_next;
 
   tp->p_state = PRREADY;
   tp->p_rdymsg = msg;
-  prio_insert(tp, &rlist.r_queue);
+//  prio_insert(tp, &rlist.r_queue);
+  while (cp->p_prio >= tp->p_prio)
+    cp = cp->p_next;
+  /* Insertion on p_prev.*/
+  tp->p_prev = (tp->p_next = cp)->p_prev;
+  tp->p_prev->p_next = cp->p_prev = tp;
+
 }
 
 /**
@@ -106,13 +113,7 @@ void chSchWakeupS(Thread *ntp, t_msg msg) {
     chSchReadyI(ntp, msg);
   else {
     Thread *otp = currp;
-    /* Note, does a prio_insert() instead of a chSchReadyI() because of the
-       relative priority between the two threads, prio_insert() scans the
-       list starting from the highest priority end downward.*/
-/*    chSchReadyI(otp, RDY_OK);*/
-    otp->p_state = PRREADY;
-    otp->p_rdymsg = RDY_OK;
-    prio_insert(otp, &rlist.r_queue);
+    chSchReadyI(otp, RDY_OK);
     (currp = ntp)->p_state = PRCURR;
     ntp->p_rdymsg = msg;
     rlist.r_preempt = CH_TIME_QUANTUM;

src/include/scheduler.h

@@ -39,6 +39,7 @@
  */
 typedef struct {
   ThreadsQueue          r_queue;
+  t_prio                r_prio;
   t_cnt                 r_preempt;
 #ifndef CH_CURRP_REGISTER_CACHE
   Thread                *r_current;

src/include/threads.h

@@ -136,10 +136,12 @@ struct Thread {
 /** Thread option: Create suspended thread.*/
 #define P_SUSPENDED 2
 
+/** Pseudo priority used by the ready list header, do not use.*/
+#define NOPRIO      0
 /** Idle thread priority.*/
-#define IDLEPRIO    0
+#define IDLEPRIO    1
 /** Lowest user priority.*/
-#define LOWPRIO     1
+#define LOWPRIO     2
 /** Normal user priority.*/
 #define NORMALPRIO  64
 /** Highest user priority.*/