6649150 add kstats to the vdev cache

3 files changed, 57 insertions, 10 deletions

diff --git a/usr/src/uts/common/fs/zfs/spa_misc.c b/usr/src/uts/common/fs/zfs/spa_misc.c
index 6b1c28140a..311bec6da7 100644
--- a/usr/src/uts/common/fs/zfs/spa_misc.c
+++ b/usr/src/uts/common/fs/zfs/spa_misc.c
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
@@ -1234,6 +1234,7 @@ spa_init(int mode)
 	zio_init();
 	dmu_init();
 	zil_init();
+	vdev_cache_stat_init();
 	zfs_prop_init();
 	zpool_prop_init();
 	spa_config_load();
@@ -1244,6 +1245,7 @@ spa_fini(void)
 {
 	spa_evict_all();
 
+	vdev_cache_stat_fini();
 	zil_fini();
 	dmu_fini();
 	zio_fini();
diff --git a/usr/src/uts/common/fs/zfs/sys/spa.h b/usr/src/uts/common/fs/zfs/sys/spa.h
index dd723df0c9..713817d89c 100644
--- a/usr/src/uts/common/fs/zfs/sys/spa.h
+++ b/usr/src/uts/common/fs/zfs/sys/spa.h
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
@@ -495,6 +495,10 @@ extern void spa_errlog_drain(spa_t *spa);
 extern void spa_errlog_sync(spa_t *spa, uint64_t txg);
 extern void spa_get_errlists(spa_t *spa, avl_tree_t *last, avl_tree_t *scrub);
 
+/* vdev cache */
+extern void vdev_cache_stat_init(void);
+extern void vdev_cache_stat_fini(void);
+
 /* Initialization and termination */
 extern void spa_init(int flags);
 extern void spa_fini(void);
diff --git a/usr/src/uts/common/fs/zfs/vdev_cache.c b/usr/src/uts/common/fs/zfs/vdev_cache.c
index 5f475f9b47..2cc059e49e 100644
--- a/usr/src/uts/common/fs/zfs/vdev_cache.c
+++ b/usr/src/uts/common/fs/zfs/vdev_cache.c
@@ -19,7 +19,7 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
@@ -29,6 +29,7 @@
 #include <sys/spa.h>
 #include <sys/vdev_impl.h>
 #include <sys/zio.h>
+#include <sys/kstat.h>
 
 /*
  * Virtual device read-ahead caching.
@@ -36,10 +37,10 @@
  * This file implements a simple LRU read-ahead cache.  When the DMU reads
  * a given block, it will often want other, nearby blocks soon thereafter.
  * We take advantage of this by reading a larger disk region and caching
- * the result.  In the best case, this can turn 256 back-to-back 512-byte
- * reads into a single 128k read followed by 255 cache hits; this reduces
+ * the result.  In the best case, this can turn 128 back-to-back 512-byte
+ * reads into a single 64k read followed by 127 cache hits; this reduces
  * latency dramatically.  In the worst case, it can turn an isolated 512-byte
- * read into a 128k read, which doesn't affect latency all that much but is
+ * read into a 64k read, which doesn't affect latency all that much but is
  * terribly wasteful of bandwidth.  A more intelligent version of the cache
  * could keep track of access patterns and not do read-ahead unless it sees
  * at least two temporally close I/Os to the same region.  Currently, only
@@ -70,14 +71,30 @@
 /*
  * All i/os smaller than zfs_vdev_cache_max will be turned into
  * 1<<zfs_vdev_cache_bshift byte reads by the vdev_cache (aka software
- * track buffer.  At most zfs_vdev_cache_size bytes will be kept in each
+ * track buffer).  At most zfs_vdev_cache_size bytes will be kept in each
  * vdev's vdev_cache.
  */
-int zfs_vdev_cache_max = 1<<14;
-int zfs_vdev_cache_size = 10ULL << 20;
+int zfs_vdev_cache_max = 1<<14;			/* 16KB */
+int zfs_vdev_cache_size = 10ULL << 20;		/* 10MB */
 int zfs_vdev_cache_bshift = 16;
 
-#define	VCBS (1 << zfs_vdev_cache_bshift)
+#define	VCBS (1 << zfs_vdev_cache_bshift)	/* 64KB */
+
+kstat_t	*vdc_ksp = NULL;
+
+typedef struct vdc_stats {
+	kstat_named_t vdc_stat_delegations;
+	kstat_named_t vdc_stat_hits;
+	kstat_named_t vdc_stat_misses;
+} vdc_stats_t;
+
+static vdc_stats_t vdc_stats = {
+	{ "delegations",	KSTAT_DATA_UINT64 },
+	{ "hits",		KSTAT_DATA_UINT64 },
+	{ "misses",		KSTAT_DATA_UINT64 }
+};
+
+#define	VDCSTAT_BUMP(stat)	atomic_add_64(&vdc_stats.stat.value.ui64, 1);
 
 static int
 vdev_cache_offset_compare(const void *a1, const void *a2)
@@ -279,6 +296,7 @@ vdev_cache_read(zio_t *zio)
 			fio->io_delegate_list = zio;
 			zio_vdev_io_bypass(zio);
 			mutex_exit(&vc->vc_lock);
+			VDCSTAT_BUMP(vdc_stat_delegations);
 			return (0);
 		}
 
@@ -287,6 +305,7 @@ vdev_cache_read(zio_t *zio)
 
 		mutex_exit(&vc->vc_lock);
 		zio_execute(zio);
+		VDCSTAT_BUMP(vdc_stat_hits);
 		return (0);
 	}
 
@@ -309,6 +328,7 @@ vdev_cache_read(zio_t *zio)
 
 	mutex_exit(&vc->vc_lock);
 	zio_nowait(fio);
+	VDCSTAT_BUMP(vdc_stat_misses);
 
 	return (0);
 }
@@ -392,3 +412,24 @@ vdev_cache_fini(vdev_t *vd)
 
 	mutex_destroy(&vc->vc_lock);
 }
+
+void
+vdev_cache_stat_init(void)
+{
+	vdc_ksp = kstat_create("zfs", 0, "vdev_cache_stats", "misc",
+	    KSTAT_TYPE_NAMED, sizeof (vdc_stats) / sizeof (kstat_named_t),
+	    KSTAT_FLAG_VIRTUAL);
+	if (vdc_ksp != NULL) {
+		vdc_ksp->ks_data = &vdc_stats;
+		kstat_install(vdc_ksp);
+	}
+}
+
+void
+vdev_cache_stat_fini(void)
+{
+	if (vdc_ksp != NULL) {
+		kstat_delete(vdc_ksp);
+		vdc_ksp = NULL;
+	}
+}