Initial stab at Venti.

src/cmd/venti/lumpqueue.c

@@ -0,0 +1,150 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+
+typedef struct LumpQueue	LumpQueue;
+typedef struct WLump		WLump;
+
+enum
+{
+	MaxLumpQ	= 1 << 3	/* max. lumps on a single write queue, must be pow 2 */
+};
+
+struct WLump
+{
+	Lump	*u;
+	Packet	*p;
+	int	creator;
+	int	gen;
+};
+
+struct LumpQueue
+{
+	QLock	lock;
+	Rendez 	flush;
+	Rendez	full;
+	Rendez	empty;
+	WLump	q[MaxLumpQ];
+	int	w;
+	int	r;
+};
+
+static LumpQueue	*lumpqs;
+static int		nqs;
+
+static QLock		glk;
+static int		gen;
+
+static void	queueproc(void *vq);
+
+int
+initlumpqueues(int nq)
+{
+	LumpQueue *q;
+
+	int i;
+	nqs = nq;
+
+	lumpqs = MKNZ(LumpQueue, nq);
+
+	for(i = 0; i < nq; i++){
+		q = &lumpqs[i];
+		q->full.l = &q->lock;
+		q->empty.l = &q->lock;
+		q->flush.l = &q->lock;
+
+		if(vtproc(queueproc, q) < 0){
+			seterr(EOk, "can't start write queue slave: %r");
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * queue a lump & it's packet data for writing
+ */
+int
+queuewrite(Lump *u, Packet *p, int creator)
+{
+	LumpQueue *q;
+	int i;
+
+	i = indexsect(mainindex, u->score);
+	if(i < 0 || i >= nqs){
+		seterr(EBug, "internal error: illegal index section in queuewrite");
+		return -1;
+	}
+
+	q = &lumpqs[i];
+
+	qlock(&q->lock);
+	while(q->r == ((q->w + 1) & (MaxLumpQ - 1)))
+		rsleep(&q->full);
+
+	q->q[q->w].u = u;
+	q->q[q->w].p = p;
+	q->q[q->w].creator = creator;
+	q->q[q->w].gen = gen;
+	q->w = (q->w + 1) & (MaxLumpQ - 1);
+
+	rwakeup(&q->empty);
+
+	qunlock(&q->lock);
+
+	return 0;
+}
+
+void
+queueflush(void)
+{
+	int i;
+	LumpQueue *q;
+
+	qlock(&glk);
+	gen++;
+	qunlock(&glk);
+
+	for(i=0; i<mainindex->nsects; i++){
+		q = &lumpqs[i];
+		qlock(&q->lock);
+		while(q->w != q->r && gen - q->q[q->r].gen > 0)
+			rsleep(&q->flush);
+		qunlock(&q->lock);
+	}
+}
+		
+static void
+queueproc(void *vq)
+{
+	LumpQueue *q;
+	Lump *u;
+	Packet *p;
+	int creator;
+
+	q = vq;
+	for(;;){
+		qlock(&q->lock);
+		while(q->w == q->r)
+			rsleep(&q->empty);
+
+		u = q->q[q->r].u;
+		p = q->q[q->r].p;
+		creator = q->q[q->r].creator;
+
+		rwakeup(&q->full);
+
+		qunlock(&q->lock);
+
+		if(writeqlump(u, p, creator) < 0)
+			fprint(2, "failed to write lump for %V: %r", u->score);
+
+		qlock(&q->lock);
+		q->r = (q->r + 1) & (MaxLumpQ - 1);
+		rwakeup(&q->flush);
+		qunlock(&q->lock);
+
+		putlump(u);
+	}
+}