[PATCH] RTO estimator cleanup patch

clean up RPC client's RTO estimator.

include/linux/sunrpc/timer.h

@@ -20,8 +20,8 @@ struct rpc_rtt {
 
 
 extern void rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo);
-extern void rpc_update_rtt(struct rpc_rtt *rt, int timer, long m);
-extern unsigned long rpc_calc_rto(struct rpc_rtt *rt, int timer);
+extern void rpc_update_rtt(struct rpc_rtt *rt, unsigned timer, long m);
+extern unsigned long rpc_calc_rto(struct rpc_rtt *rt, unsigned timer);
 
 static inline void rpc_inc_timeo(struct rpc_rtt *rt)
 {

include/linux/sunrpc/xprt.h

@@ -71,7 +71,7 @@ struct rpc_timeout {
 				to_initval,		/* initial timeout */
 				to_maxval,		/* max timeout */
 				to_increment;		/* if !exponential */
-	short			to_retries;		/* max # of retries */
+	unsigned int		to_retries;		/* max # of retries */
 	unsigned char		to_exponential;
 };
 

net/sunrpc/timer.c

+/*
+ * linux/net/sunrpc/timer.c
+ *
+ * Estimate RPC request round trip time.
+ *
+ * Based on packet round-trip and variance estimator algorithms described
+ * in appendix A of "Congestion Avoidance and Control" by Van Jacobson
+ * and Michael J. Karels (ACM Computer Communication Review; Proceedings
+ * of the Sigcomm '88 Symposium in Stanford, CA, August, 1988).
+ *
+ * This RTT estimator is used only for RPC over datagram protocols.
+ *
+ * Copyright (C) 2002 Trond Myklebust <trond.myklebust@fys.uio.no>
+ */
+
+#include <asm/param.h>
+
 #include <linux/version.h>
 #include <linux/types.h>
 #include <linux/unistd.h>
@@ -15,18 +32,25 @@ rpc_init_rtt(struct rpc_rtt *rt, unsigned long timeo)
 {
 	unsigned long init = 0;
 	unsigned i;
+
 	rt->timeo = timeo;
+
 	if (timeo > RPC_RTO_INIT)
 		init = (timeo - RPC_RTO_INIT) << 3;
 	for (i = 0; i < 5; i++) {
 		rt->srtt[i] = init;
 		rt->sdrtt[i] = RPC_RTO_INIT;
 	}
+
 	atomic_set(&rt->ntimeouts, 0);
 }
 
+/*
+ * NB: When computing the smoothed RTT and standard deviation,
+ *     be careful not to produce negative intermediate results.
+ */
 void
-rpc_update_rtt(struct rpc_rtt *rt, int timer, long m)
+rpc_update_rtt(struct rpc_rtt *rt, unsigned timer, long m)
 {
 	unsigned long *srtt, *sdrtt;
 
@@ -36,16 +60,21 @@ rpc_update_rtt(struct rpc_rtt *rt, int timer, long m)
 	/* jiffies wrapped; ignore this one */
 	if (m < 0)
 		return;
+
 	if (m == 0)
-		m = 1;
+		m = 1L;
+
 	srtt = &rt->srtt[timer];
 	m -= *srtt >> 3;
 	*srtt += m;
+
 	if (m < 0)
 		m = -m;
+
 	sdrtt = &rt->sdrtt[timer];
 	m -= *sdrtt >> 2;
 	*sdrtt += m;
+
 	/* Set lower bound on the variance */
 	if (*sdrtt < RPC_RTO_MIN)
 		*sdrtt = RPC_RTO_MIN;
@@ -65,13 +94,16 @@ rpc_update_rtt(struct rpc_rtt *rt, int timer, long m)
  */
 
 unsigned long
-rpc_calc_rto(struct rpc_rtt *rt, int timer)
+rpc_calc_rto(struct rpc_rtt *rt, unsigned timer)
 {
 	unsigned long res;
+
 	if (timer-- == 0)
 		return rt->timeo;
+
 	res = (rt->srtt[timer] >> 3) + rt->sdrtt[timer];
 	if (res > RPC_RTO_MAX)
 		res = RPC_RTO_MAX;
+
 	return res;
 }

net/sunrpc/xprt.c

@@ -584,9 +584,11 @@ xprt_complete_rqst(struct rpc_xprt *xprt, struct rpc_rqst *req, int copied)
 		xprt_adjust_cwnd(xprt, copied);
 		__xprt_put_cong(xprt, req);
 	       	if (!req->rq_nresend) {
-			int timer = rpcproc_timer(clnt, task->tk_msg.rpc_proc);
+			unsigned timer =
+				rpcproc_timer(clnt, task->tk_msg.rpc_proc);
 			if (timer)
-				rpc_update_rtt(&clnt->cl_rtt, timer, (long)jiffies - req->rq_xtime);
+				rpc_update_rtt(&clnt->cl_rtt, timer,
+						(long)jiffies - req->rq_xtime);
 		}
 		rpc_clear_timeo(&clnt->cl_rtt);
 	}