NFS: introduce mechanism for tracking NFS client metrics

Add a per-superblock performance counter facility to the NFS client.  This
facility mimics the counters available for block devices and for
networking.  Expose these new counters via the new /proc/self/mountstats
interface.

Thanks to Andrew Morton and Trond Myklebust for their review and comments.

Test plan:
fsx and iozone on UP and SMP systems, with and without pre-emption.  Watch
for memory overwrite bugs, and performance loss (significantly more CPU
required per op).

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

1 files changed, 152 insertions, 0 deletions

diff --git a/fs/nfs/iostat.h b/fs/nfs/iostat.h
new file mode 100644
index 000000000000..dc080e50ec57
--- /dev/null
+++ b/fs/nfs/iostat.h
@@ -0,0 +1,152 @@
+/*
+ *  linux/fs/nfs/iostat.h
+ *
+ *  Declarations for NFS client per-mount statistics
+ *
+ *  Copyright (C) 2005, 2006 Chuck Lever <cel@netapp.com>
+ *
+ *  NFS client per-mount statistics provide information about the health of
+ *  the NFS client and the health of each NFS mount point.  Generally these
+ *  are not for detailed problem diagnosis, but simply to indicate that there
+ *  is a problem.
+ *
+ *  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.
+ */
+
+#ifndef _NFS_IOSTAT
+#define _NFS_IOSTAT
+
+#define NFS_IOSTAT_VERS         "1.0"
+
+/*
+ * NFS byte counters
+ *
+ * 1.  SERVER - the number of payload bytes read from or written to the
+ *     server by the NFS client via an NFS READ or WRITE request.
+ *
+ * 2.  NORMAL - the number of bytes read or written by applications via
+ *     the read(2) and write(2) system call interfaces.
+ *
+ * 3.  DIRECT - the number of bytes read or written from files opened
+ *     with the O_DIRECT flag.
+ *
+ * These counters give a view of the data throughput into and out of the NFS
+ * client.  Comparing the number of bytes requested by an application with the
+ * number of bytes the client requests from the server can provide an
+ * indication of client efficiency (per-op, cache hits, etc).
+ *
+ * These counters can also help characterize which access methods are in
+ * use.  DIRECT by itself shows whether there is any O_DIRECT traffic.
+ * NORMAL + DIRECT shows how much data is going through the system call
+ * interface.  A large amount of SERVER traffic without much NORMAL or
+ * DIRECT traffic shows that applications are using mapped files.
+ *
+ * NFS page counters
+ *
+ * These count the number of pages read or written via nfs_readpage(),
+ * nfs_readpages(), or their write equivalents.
+ */
+enum nfs_stat_bytecounters {
+        NFSIOS_NORMALREADBYTES = 0,
+        NFSIOS_NORMALWRITTENBYTES,
+        NFSIOS_DIRECTREADBYTES,
+        NFSIOS_DIRECTWRITTENBYTES,
+        NFSIOS_SERVERREADBYTES,
+        NFSIOS_SERVERWRITTENBYTES,
+        NFSIOS_READPAGES,
+        NFSIOS_WRITEPAGES,
+        __NFSIOS_BYTESMAX,
+};
+
+/*
+ * NFS event counters
+ *
+ * These counters provide a low-overhead way of monitoring client activity
+ * without enabling NFS trace debugging.  The counters show the rate at
+ * which VFS requests are made, and how often the client invalidates its
+ * data and attribute caches.  This allows system administrators to monitor
+ * such things as how close-to-open is working, and answer questions such
+ * as "why are there so many GETATTR requests on the wire?"
+ *
+ * They also count anamolous events such as short reads and writes, silly
+ * renames due to close-after-delete, and operations that change the size
+ * of a file (such operations can often be the source of data corruption
+ * if applications aren't using file locking properly).
+ */
+enum nfs_stat_eventcounters {
+        NFSIOS_INODEREVALIDATE = 0,
+        NFSIOS_DENTRYREVALIDATE,
+        NFSIOS_DATAINVALIDATE,
+        NFSIOS_ATTRINVALIDATE,
+        NFSIOS_VFSOPEN,
+        NFSIOS_VFSLOOKUP,
+        NFSIOS_VFSACCESS,
+        NFSIOS_VFSUPDATEPAGE,
+        NFSIOS_VFSREADPAGE,
+        NFSIOS_VFSREADPAGES,
+        NFSIOS_VFSWRITEPAGE,
+        NFSIOS_VFSWRITEPAGES,
+        NFSIOS_VFSGETDENTS,
+        NFSIOS_VFSSETATTR,
+        NFSIOS_VFSFLUSH,
+        NFSIOS_VFSFSYNC,
+        NFSIOS_VFSLOCK,
+        NFSIOS_VFSRELEASE,
+        NFSIOS_CONGESTIONWAIT,
+        NFSIOS_SETATTRTRUNC,
+        NFSIOS_EXTENDWRITE,
+        NFSIOS_SILLYRENAME,
+        NFSIOS_SHORTREAD,
+        NFSIOS_SHORTWRITE,
+        __NFSIOS_COUNTSMAX,
+};
+
+#ifdef __KERNEL__
+
+#include <linux/percpu.h>
+#include <linux/cache.h>
+
+struct nfs_iostats {
+        unsigned long long      bytes[__NFSIOS_BYTESMAX];
+        unsigned long           events[__NFSIOS_COUNTSMAX];
+} ____cacheline_aligned;
+
+static inline void nfs_inc_stats(struct inode *inode, enum nfs_stat_eventcounters stat)
+{
+        struct nfs_iostats *iostats;
+        int cpu;
+
+        cpu = get_cpu();
+        iostats = per_cpu_ptr(NFS_SERVER(inode)->io_stats, cpu);
+        iostats->events[stat] ++;
+        put_cpu_no_resched();
+}
+
+static inline void nfs_add_stats(struct inode *inode, enum nfs_stat_bytecounters stat, unsigned long addend)
+{
+        struct nfs_iostats *iostats;
+        int cpu;
+
+        cpu = get_cpu();
+        iostats = per_cpu_ptr(NFS_SERVER(inode)->io_stats, cpu);
+        iostats->bytes[stat] += addend;
+        put_cpu_no_resched();
+}
+
+static inline struct nfs_iostats *nfs_alloc_iostats(void)
+{
+        return alloc_percpu(struct nfs_iostats);
+}
+
+static inline void nfs_free_iostats(struct nfs_iostats *stats)
+{
+        free_percpu(stats);
+}
+
+#endif
+#endif