From b0f3ee385e17e220fd6599867abcc828b0b28e25 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Sun, 16 Mar 2003 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2003-03-16

---
 port/devproc.c |   5 +-
 port/proc.c    | 131 +++++++++++++++++++++++++++++++++----------------
 2 files changed, 91 insertions(+), 45 deletions(-)

diff --git a/port/devproc.c b/port/devproc.c
index 7db88b29ad0c6f8057f68955f6cbac5b4aca8167..63f76603b33972aab63beadcd28136c7077c2e4d 100644
--- a/port/devproc.c
+++ b/port/devproc.c
@@ -1147,9 +1147,10 @@ procctlreq(Proc *p, char *va, int n)
 		procpriority(p, pri, 0);
 		break;
 	case CMfixedpri:
-		if(!iseve())
+		pri = atoi(cb->f[1]);
+		if(pri > PriNormal && !iseve())
 			error(Eperm);
-		procpriority(p, atoi(cb->f[1]), 1);
+		procpriority(p, pri, 1);
 		break;
 	case CMprivate:
 		p->privatemem = 1;
diff --git a/port/proc.c b/port/proc.c
index 179c57edd81039b1bf4dfb258102e740a481ddbc..8a3ad8d3693147d07f82f119874cf9362b17d35a 100644
--- a/port/proc.c
+++ b/port/proc.c
@@ -260,17 +260,92 @@ ready(Proc *p)
 }
 
 /*
- *  yield the processor to any other runnable process
+ *  remove a process from a scheduling queue (called splhi)
+ */
+static Proc*
+dequeueproc(Schedq *rq, Proc *tp)
+{
+	Proc *l, *p;
+
+	if(!canlock(runq))
+		return nil;
+
+	/*
+	 *  the queue may have changed before we locked runq,
+	 *  refind the target process.
+	 */
+	l = 0;
+	for(p = rq->head; p; p = p->rnext){
+		if(p == tp)
+			break;
+		l = p;
+	}
+
+	/*
+	 *  p->mach==0 only when process state is saved
+	 */
+	if(p == 0 || p->mach){
+		unlock(runq);
+		return nil;
+	}
+	if(p->rnext == 0)
+		rq->tail = l;
+	if(l)
+		l->rnext = p->rnext;
+	else
+		rq->head = p->rnext;
+	if(rq->head == nil)
+		runvec &= ~(1<<(rq-runq));
+	rq->n--;
+	nrdy--;
+	if(p->state != Ready)
+		print("dequeueproc %s %lud %s\n", p->text, p->pid, statename[p->state]);
+
+	unlock(runq);
+	return p;
+}
+
+/*
+ *  yield the processor and drop our priority
  */
 void
 yield(void)
 {
 	if(anyready()){
-		up->yield = 1;
+		up->quanta = 0;	/* act like you used them all up */
 		sched();
 	}
 }
 
+/*
+ *  move up any process waiting more than its quanta
+ */
+static void
+rebalance(void)
+{
+	Schedq *rq;
+	Proc *p;
+
+	for(rq = runq; rq < &runq[Nrq]; rq++){
+		p = rq->head;
+		if(p == nil)
+			continue;
+		if(p->mp != MACHP(m->machno))
+			continue;
+		if(p->priority == p->basepri)
+			continue;
+		if(m->ticks - p->readytime < quanta[p->priority]/4)
+			continue;
+		splhi();
+		p = dequeueproc(rq, p);
+		spllo();
+		if(p == nil)
+			continue;
+		p->quanta = quanta[p->priority];	/* act like we used none */
+		ready(p);
+	}
+}
+
 /*
  *  pick a process to run
  */
@@ -278,7 +353,7 @@ Proc*
 runproc(void)
 {
 	Schedq *rq;
-	Proc *p, *l, *tp;
+	Proc *p;
 	ulong start, now;
 	int i;
 
@@ -287,6 +362,11 @@ runproc(void)
 	if ((p = edf->edfrunproc()) != nil)
 		return p;
 
+	if(m->fairness++ == 10){
+		m->fairness = 0;
+		rebalance();
+	}
+
 loop:
 	/*
 	 *  find a process that last ran on this processor (affinity),
@@ -301,13 +381,9 @@ loop:
 		 *
 		 */
 		for(rq = &runq[Nrq-1]; rq >= runq; rq--){
-			for(tp = rq->head; tp; tp = tp->rnext){
-				if(tp->yield){
-					tp->yield = 0;
-					continue;
-				}	
-				if(tp->mp == nil || tp->mp == MACHP(m->machno)
-				|| (!tp->wired && i > 0))
+			for(p = rq->head; p; p = p->rnext){
+				if(p->mp == nil || p->mp == MACHP(m->machno)
+				|| (!p->wired && i > 0))
 					goto found;
 			}
 		}
@@ -323,40 +399,9 @@ loop:
 
 found:
 	splhi();
-	if(!canlock(runq))
-		goto loop;
-
-	/*
-	 *  the queue may have changed before we locked runq,
-	 *  refind the target process.
-	 */
-	l = 0;
-	for(p = rq->head; p; p = p->rnext){
-		if(p == tp)
-			break;
-		l = p;
-	}
-
-	/*
-	 *  p->mach==0 only when process state is saved
-	 */
-	if(p == 0 || p->mach){
-		unlock(runq);
+	p = dequeueproc(rq, p);
+	if(p == nil)
 		goto loop;
-	}
-	if(p->rnext == 0)
-		rq->tail = l;
-	if(l)
-		l->rnext = p->rnext;
-	else
-		rq->head = p->rnext;
-	if(rq->head == nil)
-		runvec &= ~(1<<(rq-runq));
-	rq->n--;
-	nrdy--;
-	if(p->state != Ready)
-		print("runproc %s %lud %s\n", p->text, p->pid, statename[p->state]);
-	unlock(runq);
 
 	p->state = Scheding;
 	p->mp = MACHP(m->machno);