git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@152 35acf78f-673a-0410-8e92-d51de3d6d3f4

3 files changed, 23 insertions, 3 deletions

diff --git a/readme.txt b/readme.txt
index 5b06953fa..e81a07358 100644
--- a/readme.txt
+++ b/readme.txt
@@ -50,6 +50,9 @@ AVR-AT90CANx-GCC       - Port on AVR AT90CAN128, not complete yet.
   various mechanisms and the correct use cases.

 - RT Semaphores subsystem removed, the Mutexes implements a better solution

   for the same problem.

+- More performance improvements to the scheduler see the remarks into the

+  chSchWakeupS() function source. The benchmark suite reports a 6% increase

+  in the context switch performance.

 - Added mutexes test cases to the test suite.

 - Modified the test suite in order to have each test case to have the same

   alignment enforced on functions. This is done to reduce MAM/Cache alignment

diff --git a/src/chmtx.c b/src/chmtx.c
index 6f53a615f..822789270 100644
--- a/src/chmtx.c
+++ b/src/chmtx.c
@@ -189,8 +189,15 @@ void chMtxUnlockS(void) {
         newprio = mp->m_queue.p_next->p_prio;

       mp = mp->m_next;

     }

-    currp->p_prio = newprio;

-    chSchWakeupS(tp, RDY_OK);

+    if (currp->p_prio == newprio)

+      chSchWakeupS(tp, RDY_OK);

+    else {

+      /* Note, changing priority and use chSchWakeupS() is wrong because the

+         internal optimization, see the chSchWakeupS() notes.*/

+      currp->p_prio = newprio;

+      chSchReadyI(tp, RDY_OK);

+      chSchRescheduleS();

+    }

   }

 }

 

diff --git a/src/chschd.c b/src/chschd.c
index e091bb0a0..78efa57f7 100644
--- a/src/chschd.c
+++ b/src/chschd.c
@@ -104,6 +104,8 @@ void chSchGoSleepS(t_tstate newstate) {
  * @note The function is not meant to be used in the user code directly.

  * @note It is equivalent to a \p chSchReadyI() followed by a

  *       \p chSchRescheduleS() but much more efficient.

+ * @note The function assumes that the invoking thread is the highest priority

+ *       thread, so you can't use it to change priority and reschedule.

  */

 void chSchWakeupS(Thread *ntp, t_msg msg) {

 

@@ -111,7 +113,15 @@ void chSchWakeupS(Thread *ntp, t_msg msg) {
     chSchReadyI(ntp, msg);

   else {

     Thread *otp = currp;

-    chSchReadyI(otp, RDY_OK);

+    /* Optimization, assumes that the invoking thread has the highest priority

+       which is always true unless the priority was willingly changed.

+       This assumption allows us to place the thread always on top of the

+       ready list without have to scan it, free lunch.*/

+/*    chSchReadyI(otp, RDY_OK);*/

+    otp->p_state = PRREADY;

+    otp->p_rdymsg = RDY_OK;

+    otp->p_next = (otp->p_prev = (Thread *)&rlist.r_queue)->p_next;

+    otp->p_next->p_prev = rlist.r_queue.p_next = otp;

     (currp = ntp)->p_state = PRCURR;

     ntp->p_rdymsg = msg;

     rlist.r_preempt = CH_TIME_QUANTUM;