[PATCH] RPC over UDP congestion control updates [1/8]

Implement the basic round trip timing algorithm in order to adapt the
timeout values for the most common NFS operations to the server's
rate of response.
Algorithm is described in Van Jacobson's paper 1998 paper
on http://www-nrg.ee.lbl.gov/nrg-papers.html, and is the same as is
used for most TCP stacks.

Following the *BSD code, we implement separate rtt timers for GETATTR,
LOOKUP, READ/READDIR/READLINK, and WRITE. In addition to this, there
is one extra timer for the COMMIT operation.
All the remaining RPC calls use the current system in which a fixed
timeout value gets set by the 'timeo' mount option.

In case of a timeout, the current exponential backoff algoritm is
implemented. Subsequent patches will improve this...

3 files changed, 30 insertions, 3 deletions

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index be4c52c62c1c..d278df00ecb9 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -15,6 +15,7 @@
 #include <linux/sunrpc/auth.h>
 #include <linux/sunrpc/stats.h>
 #include <linux/sunrpc/xdr.h>
+#include <linux/sunrpc/timer.h>
 #include <asm/signal.h>
 
 /*
@@ -52,6 +53,8 @@ struct rpc_clnt {
 	unsigned int		cl_flags;	/* misc client flags */
 	unsigned long		cl_hardmax;	/* max hard timeout */
 
+	struct rpc_rtt		cl_rtt;		/* RTO estimator data */
+
 	struct rpc_portmap	cl_pmap;	/* port mapping */
 	struct rpc_wait_queue	cl_bindwait;	/* waiting on getport() */
 
@@ -91,6 +94,7 @@ struct rpc_procinfo {
 	kxdrproc_t		p_decode;	/* XDR decode function */
 	unsigned int		p_bufsiz;	/* req. buffer size */
 	unsigned int		p_count;	/* call count */
+	unsigned int		p_timer;	/* Which RTT timer to use */
 };
 
 #define rpcproc_bufsiz(clnt, proc)	((clnt)->cl_procinfo[proc].p_bufsiz)
@@ -98,6 +102,7 @@ struct rpc_procinfo {
 #define rpcproc_decode(clnt, proc)	((clnt)->cl_procinfo[proc].p_decode)
 #define rpcproc_name(clnt, proc)	((clnt)->cl_procinfo[proc].p_procname)
 #define rpcproc_count(clnt, proc)	((clnt)->cl_procinfo[proc].p_count)
+#define rpcproc_timer(clnt, proc)	((clnt)->cl_procinfo[proc].p_timer)
 
 #define RPC_CONGESTED(clnt)	(RPCXPRT_CONGESTED((clnt)->cl_xprt))
 #define RPC_PEERADDR(clnt)	(&(clnt)->cl_xprt->addr)
diff --git a/include/linux/sunrpc/timer.h b/include/linux/sunrpc/timer.h
new file mode 100644
index 000000000000..5f59407fed49
--- /dev/null
+++ b/include/linux/sunrpc/timer.h
@@ -0,0 +1,23 @@
+/*
+ *  linux/include/linux/sunrpc/timer.h
+ *
+ *  Declarations for the RPC transport timer.
+ *
+ *  Copyright (C) 2002 Trond Myklebust <trond.myklebust@fys.uio.no>
+ */
+
+#ifndef _LINUX_SUNRPC_TIMER_H
+#define _LINUX_SUNRPC_TIMER_H
+
+struct rpc_rtt {
+	long timeo;		/* default timeout value */
+	long srtt[5];		/* smoothed round trip time << 3 */
+	long sdrtt[5];		/* soothed medium deviation of RTT */
+};
+
+
+extern void rpc_init_rtt(struct rpc_rtt *rt, long timeo);
+extern void rpc_update_rtt(struct rpc_rtt *rt, int timer, long m);
+extern long rpc_calc_rto(struct rpc_rtt *rt, int timer);
+
+#endif /* _LINUX_SUNRPC_TIMER_H */
diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
index 31a27bf00e41..2759e979b351 100644
--- a/include/linux/sunrpc/xprt.h
+++ b/include/linux/sunrpc/xprt.h
@@ -98,9 +98,8 @@ struct rpc_rqst {
 	
 	u32			rq_bytes_sent;	/* Bytes we have sent */
 
-#ifdef RPC_PROFILE
-	unsigned long		rq_xtime;	/* when transmitted */
-#endif
+	long			rq_xtime;	/* when transmitted */
+	int			rq_nresend;
 };
 #define rq_svec			rq_snd_buf.head
 #define rq_slen			rq_snd_buf.len