SUNRPC: provide a mechanism for collecting stats in the RPC client

Add a simple mechanism for collecting stats in the RPC client.  Stats are
tabulated during xprt_release.  Note that per_cpu shenanigans are not
required here because the RPC client already serializes on the transport
write lock.

Test plan:
Compile kernel with CONFIG_NFS enabled.  Basic performance regression
testing with high-speed networking and high performance server.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

5 files changed, 192 insertions, 4 deletions

diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index f147e6b84332..0f3662002ffc 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -45,7 +45,8 @@ struct rpc_clnt {
         char *                  cl_server;      /* server machine name */
         char *                  cl_protname;    /* protocol name */
         struct rpc_auth *       cl_auth;        /* authenticator */
-        struct rpc_stat *       cl_stats;       /* statistics */
+        struct rpc_stat *       cl_stats;       /* per-program statistics */
+        struct rpc_iostats *    cl_metrics;     /* per-client statistics */
 
         unsigned int            cl_softrtry : 1,/* soft timeouts */
                                 cl_intr     : 1,/* interruptible */
diff --git a/include/linux/sunrpc/metrics.h b/include/linux/sunrpc/metrics.h
new file mode 100644
index 000000000000..8f96e9dc369a
--- /dev/null
+++ b/include/linux/sunrpc/metrics.h
@@ -0,0 +1,77 @@
+/*
+ *  linux/include/linux/sunrpc/metrics.h
+ *
+ *  Declarations for RPC client per-operation metrics
+ *
+ *  Copyright (C) 2005  Chuck Lever <cel@netapp.com>
+ *
+ *  RPC client per-operation statistics provide latency and retry
+ *  information about each type of RPC procedure in a given RPC program.
+ *  These statistics are not for detailed problem diagnosis, but simply
+ *  to indicate whether the problem is local or remote.
+ *
+ *  These counters are not meant to be human-readable, but are meant to be
+ *  integrated into system monitoring tools such as "sar" and "iostat".  As
+ *  such, the counters are sampled by the tools over time, and are never
+ *  zeroed after a file system is mounted.  Moving averages can be computed
+ *  by the tools by taking the difference between two instantaneous samples
+ *  and dividing that by the time between the samples.
+ *
+ *  The counters are maintained in a single array per RPC client, indexed
+ *  by procedure number.  There is no need to maintain separate counter
+ *  arrays per-CPU because these counters are always modified behind locks.
+ */
+
+#ifndef _LINUX_SUNRPC_METRICS_H
+#define _LINUX_SUNRPC_METRICS_H
+
+#include <linux/seq_file.h>
+
+#define RPC_IOSTATS_VERS        "1.0"
+
+struct rpc_iostats {
+        /*
+         * These counters give an idea about how many request
+         * transmissions are required, on average, to complete that
+         * particular procedure.  Some procedures may require more
+         * than one transmission because the server is unresponsive,
+         * the client is retransmitting too aggressively, or the
+         * requests are large and the network is congested.
+         */
+        unsigned long           om_ops,         /* count of operations */
+                                om_ntrans,      /* count of RPC transmissions */
+                                om_timeouts;    /* count of major timeouts */
+
+        /*
+         * These count how many bytes are sent and received for a
+         * given RPC procedure type.  This indicates how much load a
+         * particular procedure is putting on the network.  These
+         * counts include the RPC and ULP headers, and the request
+         * payload.
+         */
+        unsigned long long      om_bytes_sent,  /* count of bytes out */
+                                om_bytes_recv;  /* count of bytes in */
+
+        /*
+         * The length of time an RPC request waits in queue before
+         * transmission, the network + server latency of the request,
+         * and the total time the request spent from init to release
+         * are measured.
+         */
+        unsigned long long      om_queue,       /* jiffies queued for xmit */
+                                om_rtt,         /* jiffies for RPC RTT */
+                                om_execute;     /* jiffies for RPC execution */
+} ____cacheline_aligned;
+
+struct rpc_task;
+struct rpc_clnt;
+
+/*
+ * EXPORTed functions for managing rpc_iostats structures
+ */
+struct rpc_iostats *    rpc_alloc_iostats(struct rpc_clnt *);
+void                    rpc_count_iostats(struct rpc_task *);
+void                    rpc_print_iostats(struct seq_file *, struct rpc_clnt *);
+void                    rpc_free_iostats(struct rpc_iostats *);
+
+#endif /* _LINUX_SUNRPC_METRICS_H */
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 84eb5b4565fc..0bb23e8e9d0c 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -28,12 +28,11 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/utsname.h>
+#include <linux/workqueue.h>
 
 #include <linux/sunrpc/clnt.h>
-#include <linux/workqueue.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
-
-#include <linux/nfs.h>
+#include <linux/sunrpc/metrics.h>
 
 
 #define RPC_SLACK_SPACE         (1024)  /* total overkill */
@@ -147,6 +146,7 @@ rpc_new_client(struct rpc_xprt *xprt, char *servname,
         clnt->cl_vers     = version->number;
         clnt->cl_prot     = xprt->prot;
         clnt->cl_stats    = program->stats;
+        clnt->cl_metrics  = rpc_alloc_iostats(clnt);
         rpc_init_wait_queue(&clnt->cl_pmap_default.pm_bindwait, "bindwait");
 
         if (!clnt->cl_port)
@@ -245,6 +245,7 @@ rpc_clone_client(struct rpc_clnt *clnt)
         if (new->cl_auth)
                 atomic_inc(&new->cl_auth->au_count);
         new->cl_pmap            = &new->cl_pmap_default;
+        new->cl_metrics         = rpc_alloc_iostats(clnt);
         rpc_init_wait_queue(&new->cl_pmap_default.pm_bindwait, "bindwait");
         return new;
 out_no_clnt:
@@ -315,6 +316,8 @@ rpc_destroy_client(struct rpc_clnt *clnt)
         if (clnt->cl_server != clnt->cl_inline_name)
                 kfree(clnt->cl_server);
 out_free:
+        rpc_free_iostats(clnt->cl_metrics);
+        clnt->cl_metrics = NULL;
         if (clnt->cl_dentry)
                 dput(clnt->cl_dentry);
         kfree(clnt);
diff --git a/net/sunrpc/stats.c b/net/sunrpc/stats.c
index 4979f226e285..24ac7163b9c7 100644
--- a/net/sunrpc/stats.c
+++ b/net/sunrpc/stats.c
@@ -21,6 +21,7 @@
 #include <linux/seq_file.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/svcsock.h>
+#include <linux/sunrpc/metrics.h>
 
 #define RPCDBG_FACILITY RPCDBG_MISC
 
@@ -106,6 +107,110 @@ void svc_seq_show(struct seq_file *seq, const struct svc_stat *statp) {
         }
 }
 
+/**
+ * rpc_alloc_iostats - allocate an rpc_iostats structure
+ * @clnt: RPC program, version, and xprt
+ *
+ */
+struct rpc_iostats *rpc_alloc_iostats(struct rpc_clnt *clnt)
+{
+        unsigned int ops = clnt->cl_maxproc;
+        size_t size = ops * sizeof(struct rpc_iostats);
+        struct rpc_iostats *new;
+
+        new = kmalloc(size, GFP_KERNEL);
+        if (new)
+                memset(new, 0 , size);
+        return new;
+}
+EXPORT_SYMBOL(rpc_alloc_iostats);
+
+/**
+ * rpc_free_iostats - release an rpc_iostats structure
+ * @stats: doomed rpc_iostats structure
+ *
+ */
+void rpc_free_iostats(struct rpc_iostats *stats)
+{
+        kfree(stats);
+}
+EXPORT_SYMBOL(rpc_free_iostats);
+
+/**
+ * rpc_count_iostats - tally up per-task stats
+ * @task: completed rpc_task
+ *
+ * Relies on the caller for serialization.
+ */
+void rpc_count_iostats(struct rpc_task *task)
+{
+        struct rpc_rqst *req = task->tk_rqstp;
+        struct rpc_iostats *stats = task->tk_client->cl_metrics;
+        struct rpc_iostats *op_metrics;
+        long rtt, execute, queue;
+
+        if (!stats || !req)
+                return;
+        op_metrics = &stats[task->tk_msg.rpc_proc->p_proc];
+
+        op_metrics->om_ops++;
+        op_metrics->om_ntrans += req->rq_ntrans;
+        op_metrics->om_timeouts += task->tk_timeouts;
+
+        op_metrics->om_bytes_sent += task->tk_bytes_sent;
+        op_metrics->om_bytes_recv += req->rq_received;
+
+        queue = (long)req->rq_xtime - task->tk_start;
+        if (queue < 0)
+                queue = -queue;
+        op_metrics->om_queue += queue;
+
+        rtt = task->tk_rtt;
+        if (rtt < 0)
+                rtt = -rtt;
+        op_metrics->om_rtt += rtt;
+
+        execute = (long)jiffies - task->tk_start;
+        if (execute < 0)
+                execute = -execute;
+        op_metrics->om_execute += execute;
+}
+
+#define MILLISECS_PER_JIFFY     (1000UL / HZ)
+
+void rpc_print_iostats(struct seq_file *seq, struct rpc_clnt *clnt)
+{
+        struct rpc_iostats *stats = clnt->cl_metrics;
+        struct rpc_xprt *xprt = clnt->cl_xprt;
+        unsigned int op, maxproc = clnt->cl_maxproc;
+
+        if (!stats)
+                return;
+
+        seq_printf(seq, "\tRPC iostats version: %s  ", RPC_IOSTATS_VERS);
+        seq_printf(seq, "p/v: %u/%u (%s)\n",
+                        clnt->cl_prog, clnt->cl_vers, clnt->cl_protname);
+
+        if (xprt)
+                xprt->ops->print_stats(xprt, seq);
+
+        seq_printf(seq, "\tper-op statistics\n");
+        for (op = 0; op < maxproc; op++) {
+                struct rpc_iostats *metrics = &stats[op];
+                seq_printf(seq, "%12u: ", op);
+                seq_printf(seq, "%lu %lu %lu %Lu %Lu %Lu %Lu %Lu\n",
+                                metrics->om_ops,
+                                metrics->om_ntrans,
+                                metrics->om_timeouts,
+                                metrics->om_bytes_sent,
+                                metrics->om_bytes_recv,
+                                metrics->om_queue * MILLISECS_PER_JIFFY,
+                                metrics->om_rtt * MILLISECS_PER_JIFFY,
+                                metrics->om_execute * MILLISECS_PER_JIFFY);
+        }
+}
+EXPORT_SYMBOL(rpc_print_iostats);
+
 /*
  * Register/unregister RPC proc files
  */
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index c6241976a6ee..eb5a262e024e 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -44,6 +44,7 @@
 #include <linux/random.h>
 
 #include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/metrics.h>
 
 /*
  * Local variables
@@ -859,6 +860,7 @@ void xprt_release(struct rpc_task *task)
 
         if (!(req = task->tk_rqstp))
                 return;
+        rpc_count_iostats(task);
         spin_lock_bh(&xprt->transport_lock);
         xprt->ops->release_xprt(xprt, task);
         if (xprt->ops->release_request)