1 files changed, 107 insertions, 0 deletions
diff --git a/net/sunrpc/timer.c b/net/sunrpc/timer.c
new file mode 100644
index 000000000000..bcbdf6430d5c
--- /dev/null
+++ b/net/sunrpc/timer.c
@@ -0,0 +1,107 @@
+/*
+ * 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/types.h>
+#include <linux/unistd.h>
+
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/xprt.h>
+#include <linux/sunrpc/timer.h>
+
+#define RPC_RTO_MAX (60*HZ)
+#define RPC_RTO_INIT (HZ/5)
+#define RPC_RTO_MIN (HZ/10)
+
+void
+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;
+		rt->ntimeouts[i] = 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, unsigned timer, long m)
+{
+	long *srtt, *sdrtt;
+
+	if (timer-- == 0)
+		return;
+
+	/* jiffies wrapped; ignore this one */
+	if (m < 0)
+		return;
+
+	if (m == 0)
+		m = 1L;
+
+	srtt = (long *)&rt->srtt[timer];
+	m -= *srtt >> 3;
+	*srtt += m;
+
+	if (m < 0)
+		m = -m;
+
+	sdrtt = (long *)&rt->sdrtt[timer];
+	m -= *sdrtt >> 2;
+	*sdrtt += m;
+
+	/* Set lower bound on the variance */
+	if (*sdrtt < RPC_RTO_MIN)
+		*sdrtt = RPC_RTO_MIN;
+}
+
+/*
+ * Estimate rto for an nfs rpc sent via. an unreliable datagram.
+ * Use the mean and mean deviation of rtt for the appropriate type of rpc
+ * for the frequent rpcs and a default for the others.
+ * The justification for doing "other" this way is that these rpcs
+ * happen so infrequently that timer est. would probably be stale.
+ * Also, since many of these rpcs are
+ * non-idempotent, a conservative timeout is desired.
+ * getattr, lookup,
+ * read, write, commit     - A+4D
+ * other                   - timeo
+ */
+
+unsigned long
+rpc_calc_rto(struct rpc_rtt *rt, unsigned timer)
+{
+	unsigned long res;
+
+	if (timer-- == 0)
+		return rt->timeo;
+
+	res = ((rt->srtt[timer] + 7) >> 3) + rt->sdrtt[timer];
+	if (res > RPC_RTO_MAX)
+		res = RPC_RTO_MAX;
+
+	return res;
+}