knfsd: add file to export stats about nfsd pools

Add /proc/fs/nfsd/pool_stats to export to userspace various
statistics about the operation of rpc server thread pools.

This patch is based on a forward-ported version of
knfsd-add-pool-thread-stats which has been shipping in the SGI
"Enhanced NFS" product since 2006 and which was previously
posted:

http://article.gmane.org/gmane.linux.nfs/10375

It has also been updated thus:

 * moved EXPORT_SYMBOL() to near the function it exports
 * made the new struct struct seq_operations const
 * used SEQ_START_TOKEN instead of ((void *)1)
 * merged fix from SGI PV 990526 "sunrpc: use dprintk instead of
   printk in svc_pool_stats_*()" by Harshula Jayasuriya.
 * merged fix from SGI PV 964001 "Crash reading pool_stats before
   nfsds are started".

Signed-off-by: Greg Banks <gnb@sgi.com>
Signed-off-by: Harshula Jayasuriya <harshula@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

4 files changed, 129 insertions, 1 deletions

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 3d93b2064ce5..4adebb6312c4 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -60,6 +60,7 @@ enum {
         NFSD_FO_UnlockFS,
         NFSD_Threads,
         NFSD_Pool_Threads,
+        NFSD_Pool_Stats,
         NFSD_Versions,
         NFSD_Ports,
         NFSD_MaxBlkSize,
@@ -172,6 +173,16 @@ static const struct file_operations exports_operations = {
         .owner          = THIS_MODULE,
 };
 
+extern int nfsd_pool_stats_open(struct inode *inode, struct file *file);
+
+static struct file_operations pool_stats_operations = {
+        .open           = nfsd_pool_stats_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+        .owner          = THIS_MODULE,
+};
+
 /*----------------------------------------------------------------------------*/
 /*
  * payload - write methods
@@ -1246,6 +1257,7 @@ static int nfsd_fill_super(struct super_block * sb, void * data, int silent)
                 [NFSD_Fh] = {"filehandle", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Threads] = {"threads", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Pool_Threads] = {"pool_threads", &transaction_ops, S_IWUSR|S_IRUSR},
+                [NFSD_Pool_Stats] = {"pool_stats", &pool_stats_operations, S_IRUGO},
                 [NFSD_Versions] = {"versions", &transaction_ops, S_IWUSR|S_IRUSR},
                 [NFSD_Ports] = {"portlist", &transaction_ops, S_IWUSR|S_IRUGO},
                 [NFSD_MaxBlkSize] = {"max_block_size", &transaction_ops, S_IWUSR|S_IRUGO},
diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index c3eb0759fd57..ef0a3686639d 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -546,3 +546,10 @@ nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp)
         nfsd_cache_update(rqstp, proc->pc_cachetype, statp + 1);
         return 1;
 }
+
+int nfsd_pool_stats_open(struct inode *inode, struct file *file)
+{
+        if (nfsd_serv == NULL)
+                return -ENODEV;
+        return svc_pool_stats_open(nfsd_serv, file);
+}
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 39ec186a492d..9f9f699dd469 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -24,6 +24,15 @@
  */
 typedef int             (*svc_thread_fn)(void *);
 
+/* statistics for svc_pool structures */
+struct svc_pool_stats {
+        unsigned long   packets;
+        unsigned long   sockets_queued;
+        unsigned long   threads_woken;
+        unsigned long   overloads_avoided;
+        unsigned long   threads_timedout;
+};
+
 /*
  *
  * RPC service thread pool.
@@ -42,6 +51,7 @@ struct svc_pool {
         unsigned int            sp_nrthreads;   /* # of threads in pool */
         struct list_head        sp_all_threads; /* all server threads */
         int                     sp_nwaking;     /* number of threads woken but not yet active */
+        struct svc_pool_stats   sp_stats;       /* statistics on pool operation */
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -396,6 +406,7 @@ struct svc_serv *  svc_create_pooled(struct svc_program *, unsigned int,
                         sa_family_t, void (*shutdown)(struct svc_serv *),
                         svc_thread_fn, struct module *);
 int                svc_set_num_threads(struct svc_serv *, struct svc_pool *, int);
+int                svc_pool_stats_open(struct svc_serv *serv, struct file *file);
 void               svc_destroy(struct svc_serv *);
 int                svc_process(struct svc_rqst *);
 int                svc_register(const struct svc_serv *, const unsigned short,
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 0551b6b6cf8c..1e66f2491460 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -318,6 +318,8 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
                 goto out_unlock;
         }
 
+        pool->sp_stats.packets++;
+
         /* Mark transport as busy. It will remain in this state until
          * the provider calls svc_xprt_received. We update XPT_BUSY
          * atomically because it also guards against trying to enqueue
@@ -355,6 +357,7 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
         if (pool->sp_nwaking >= SVC_MAX_WAKING) {
                 /* too many threads are runnable and trying to wake up */
                 thread_avail = 0;
+                pool->sp_stats.overloads_avoided++;
         }
 
         if (thread_avail) {
@@ -374,11 +377,13 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
                 atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
                 rqstp->rq_waking = 1;
                 pool->sp_nwaking++;
+                pool->sp_stats.threads_woken++;
                 BUG_ON(xprt->xpt_pool != pool);
                 wake_up(&rqstp->rq_wait);
         } else {
                 dprintk("svc: transport %p put into queue\n", xprt);
                 list_add_tail(&xprt->xpt_ready, &pool->sp_sockets);
+                pool->sp_stats.sockets_queued++;
                 BUG_ON(xprt->xpt_pool != pool);
         }
 
@@ -591,6 +596,7 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
         int                     pages;
         struct xdr_buf          *arg;
         DECLARE_WAITQUEUE(wait, current);
+        long                    time_left;
 
         dprintk("svc: server %p waiting for data (to = %ld)\n",
                 rqstp, timeout);
@@ -676,12 +682,14 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
                 add_wait_queue(&rqstp->rq_wait, &wait);
                 spin_unlock_bh(&pool->sp_lock);
 
-                schedule_timeout(timeout);
+                time_left = schedule_timeout(timeout);
 
                 try_to_freeze();
 
                 spin_lock_bh(&pool->sp_lock);
                 remove_wait_queue(&rqstp->rq_wait, &wait);
+                if (!time_left)
+                        pool->sp_stats.threads_timedout++;
 
                 xprt = rqstp->rq_xprt;
                 if (!xprt) {
@@ -1114,3 +1122,93 @@ int svc_xprt_names(struct svc_serv *serv, char *buf, int buflen)
         return totlen;
 }
 EXPORT_SYMBOL_GPL(svc_xprt_names);
+
+
+/*----------------------------------------------------------------------------*/
+
+static void *svc_pool_stats_start(struct seq_file *m, loff_t *pos)
+{
+        unsigned int pidx = (unsigned int)*pos;
+        struct svc_serv *serv = m->private;
+
+        dprintk("svc_pool_stats_start, *pidx=%u\n", pidx);
+
+        lock_kernel();
+        /* bump up the pseudo refcount while traversing */
+        svc_get(serv);
+        unlock_kernel();
+
+        if (!pidx)
+                return SEQ_START_TOKEN;
+        return (pidx > serv->sv_nrpools ? NULL : &serv->sv_pools[pidx-1]);
+}
+
+static void *svc_pool_stats_next(struct seq_file *m, void *p, loff_t *pos)
+{
+        struct svc_pool *pool = p;
+        struct svc_serv *serv = m->private;
+
+        dprintk("svc_pool_stats_next, *pos=%llu\n", *pos);
+
+        if (p == SEQ_START_TOKEN) {
+                pool = &serv->sv_pools[0];
+        } else {
+                unsigned int pidx = (pool - &serv->sv_pools[0]);
+                if (pidx < serv->sv_nrpools-1)
+                        pool = &serv->sv_pools[pidx+1];
+                else
+                        pool = NULL;
+        }
+        ++*pos;
+        return pool;
+}
+
+static void svc_pool_stats_stop(struct seq_file *m, void *p)
+{
+        struct svc_serv *serv = m->private;
+
+        lock_kernel();
+        /* this function really, really should have been called svc_put() */
+        svc_destroy(serv);
+        unlock_kernel();
+}
+
+static int svc_pool_stats_show(struct seq_file *m, void *p)
+{
+        struct svc_pool *pool = p;
+
+        if (p == SEQ_START_TOKEN) {
+                seq_puts(m, "# pool packets-arrived sockets-enqueued threads-woken overloads-avoided threads-timedout\n");
+                return 0;
+        }
+
+        seq_printf(m, "%u %lu %lu %lu %lu %lu\n",
+                pool->sp_id,
+                pool->sp_stats.packets,
+                pool->sp_stats.sockets_queued,
+                pool->sp_stats.threads_woken,
+                pool->sp_stats.overloads_avoided,
+                pool->sp_stats.threads_timedout);
+
+        return 0;
+}
+
+static const struct seq_operations svc_pool_stats_seq_ops = {
+        .start  = svc_pool_stats_start,
+        .next   = svc_pool_stats_next,
+        .stop   = svc_pool_stats_stop,
+        .show   = svc_pool_stats_show,
+};
+
+int svc_pool_stats_open(struct svc_serv *serv, struct file *file)
+{
+        int err;
+
+        err = seq_open(file, &svc_pool_stats_seq_ops);
+        if (!err)
+                ((struct seq_file *) file->private_data)->private = serv;
+        return err;
+}
+EXPORT_SYMBOL(svc_pool_stats_open);
+
+/*----------------------------------------------------------------------------*/