diff --git a/include/sys/zfs_context.h b/include/sys/zfs_context.h
index 4abafcc6f1b8..e4af6fc378b5 100644
--- a/include/sys/zfs_context.h
+++ b/include/sys/zfs_context.h
@@ -134,10 +134,9 @@ extern int aok;
  * ZFS debugging
  */
 
-#ifdef ZFS_DEBUG
 extern void dprintf_setup(int *argc, char **argv);
-#endif /* ZFS_DEBUG */
-
+extern void __dprintf(const char *file, const char *func,
+    int line, const char *fmt, ...);
 extern void cmn_err(int, const char *, ...);
 extern void vcmn_err(int, const char *, __va_list);
 extern void panic(const char *, ...);
diff --git a/include/sys/zfs_debug.h b/include/sys/zfs_debug.h
index f08d7cd2bc8e..e83b66147cfe 100644
--- a/include/sys/zfs_debug.h
+++ b/include/sys/zfs_debug.h
@@ -25,10 +25,6 @@
 #ifndef _SYS_ZFS_DEBUG_H
 #define	_SYS_ZFS_DEBUG_H
 
-#ifdef	__cplusplus
-extern "C" {
-#endif
-
 #ifndef TRUE
 #define	TRUE 1
 #endif
@@ -38,14 +34,14 @@ extern "C" {
 #endif
 
 /*
- * ZFS debugging
+ * ZFS debugging - Always enabled for user space builds.
  */
-
 #if defined(DEBUG) || !defined(_KERNEL)
 #define	ZFS_DEBUG
 #endif
 
 extern int zfs_flags;
+extern int zfs_recover;
 
 #define	ZFS_DEBUG_DPRINTF	0x0001
 #define	ZFS_DEBUG_DBUF_VERIFY	0x0002
@@ -53,43 +49,33 @@ extern int zfs_flags;
 #define	ZFS_DEBUG_SNAPNAMES	0x0008
 #define	ZFS_DEBUG_MODIFY	0x0010
 
-#ifdef ZFS_DEBUG
-#if defined(_KERNEL) && defined(HAVE_SPL)
 /*
- * Log ZFS debug messages as the spl SS_USER1 subsystem.
+ * Always log zfs debug messages to the spl debug subsystem as SS_USER1.
+ * When the SPL is configured with debugging enabled these messages will
+ * appear in the internal spl debug log, otherwise they are a no-op.
  */
+#if defined(_KERNEL)
+
 #include <spl-debug.h>
+#define	dprintf(...)                                                   \
+	if (zfs_flags & ZFS_DEBUG_DPRINTF)                             \
+		__SDEBUG(NULL, SS_USER1, SD_DPRINTF, __VA_ARGS__)
 
-#ifdef SS_DEBUG_SUBSYS
-#undef SS_DEBUG_SUBSYS
-#endif
-#define SS_DEBUG_SUBSYS SS_USER1
-#define dprintf(...) SDEBUG_LIMIT(SD_DPRINTF, __VA_ARGS__)
+/*
+ * When zfs is running is user space the debugging is always enabled.
+ * The messages will be printed using the __dprintf() function and
+ * filtered based on the zfs_flags variable.
+ */
 #else
-extern void __dprintf(const char *file, const char *func,
-    int line, const char *fmt, ...);
-#define	dprintf(...) \
-	if (zfs_flags & ZFS_DEBUG_DPRINTF) \
+#define dprintf(...)                                                   \
+	if (zfs_flags & ZFS_DEBUG_DPRINTF)                             \
 		__dprintf(__FILE__, __func__, __LINE__, __VA_ARGS__)
-#endif /* _KERNEL && HAVE_SPL */
-#else
-#define	dprintf(...) ((void)0)
-#endif /* ZFS_DEBUG */
 
-extern void zfs_panic_recover(const char *fmt, ...);
+#endif /* _KERNEL */
 
-typedef struct zfs_dbgmsg {
-	list_node_t zdm_node;
-	time_t zdm_timestamp;
-	char zdm_msg[1]; /* variable length allocation */
-} zfs_dbgmsg_t;
-
-extern void zfs_dbgmsg_init(void);
-extern void zfs_dbgmsg_fini(void);
-extern void zfs_dbgmsg(const char *fmt, ...);
-
-#ifdef	__cplusplus
-}
-#endif
+void zfs_panic_recover(const char *fmt, ...);
+#define	zfs_dbgmsg(...)	dprintf(__VA_ARGS__)
+void zfs_dbgmsg_init(void);
+void zfs_dbgmsg_fini(void);
 
 #endif	/* _SYS_ZFS_DEBUG_H */
diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 002276a90db7..69fbd44cd1ff 100644
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -700,8 +700,6 @@ fop_getattr(vnode_t *vp, vattr_t *vap)
 	return (0);
 }
 
-#ifdef ZFS_DEBUG
-
 /*
  * =========================================================================
  * Figure out which debugging statements to print
@@ -814,8 +812,6 @@ __dprintf(const char *file, const char *func, int line, const char *fmt, ...)
 	}
 }
 
-#endif /* ZFS_DEBUG */
-
 /*
  * =========================================================================
  * cmn_err() and panic()
diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index 95d14a9e7511..2220c4d9de01 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -885,7 +885,6 @@ buf_dest(void *vbuf, void *unused)
 static void
 hdr_recl(void *unused)
 {
-	dprintf("hdr_recl called\n");
 	/*
 	 * umem calls the reclaim func when we destroy the buf cache,
 	 * which is after we do arc_fini().
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index e4e0c35f01df..1016ac7beb0f 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -234,21 +234,6 @@ static avl_tree_t spa_l2cache_avl;
 kmem_cache_t *spa_buffer_pool;
 int spa_mode_global;
 
-#ifdef ZFS_DEBUG
-/* Everything except dprintf is on by default in debug builds */
-int zfs_flags = ~ZFS_DEBUG_DPRINTF;
-#else
-int zfs_flags = 0;
-#endif
-
-/*
- * zfs_recover can be set to nonzero to attempt to recover from
- * otherwise-fatal errors, typically caused by on-disk corruption.  When
- * set, calls to zfs_panic_recover() will turn into warning messages.
- */
-int zfs_recover = 0;
-
-
 /*
  * ==========================================================================
  * SPA config locking
@@ -1217,16 +1202,6 @@ spa_freeze(spa_t *spa)
 		txg_wait_synced(spa_get_dsl(spa), freeze_txg);
 }
 
-void
-zfs_panic_recover(const char *fmt, ...)
-{
-	va_list adx;
-
-	va_start(adx, fmt);
-	vcmn_err(zfs_recover ? CE_WARN : CE_PANIC, fmt, adx);
-	va_end(adx);
-}
-
 /*
  * This is a stripped-down version of strtoull, suitable only for converting
  * lowercase hexidecimal numbers that don't overflow.
@@ -1765,7 +1740,4 @@ EXPORT_SYMBOL(spa_writeable);
 EXPORT_SYMBOL(spa_mode);
 
 EXPORT_SYMBOL(spa_namespace_lock);
-
-module_param(zfs_recover, int, 0644);
-MODULE_PARM_DESC(zfs_recover, "Set to attempt to recover from fatal errors");
 #endif
diff --git a/module/zfs/zfs_debug.c b/module/zfs/zfs_debug.c
index d0f411a99350..f4b5e6fa1513 100644
--- a/module/zfs/zfs_debug.c
+++ b/module/zfs/zfs_debug.c
@@ -24,72 +24,60 @@
 
 #include <sys/zfs_context.h>
 
-list_t zfs_dbgmsgs;
-int zfs_dbgmsg_size;
-kmutex_t zfs_dbgmsgs_lock;
-int zfs_dbgmsg_maxsize = 1<<20; /* 1MB */
+/*
+ * Enable various debugging features.
+ */
+int zfs_flags = 0;
 
+/*
+ * zfs_recover can be set to nonzero to attempt to recover from
+ * otherwise-fatal errors, typically caused by on-disk corruption.  When
+ * set, calls to zfs_panic_recover() will turn into warning messages.
+ */
+int zfs_recover = 0;
+
+
+void
+zfs_panic_recover(const char *fmt, ...)
+{
+	va_list adx;
+
+	va_start(adx, fmt);
+	vcmn_err(zfs_recover ? CE_WARN : CE_PANIC, fmt, adx);
+	va_end(adx);
+}
+
+/*
+ * Debug logging is enabled by default for production kernel builds.
+ * The overhead for this is negligible and the logs can be valuable when
+ * debugging.  For non-production user space builds all debugging except
+ * logging is enabled since performance is no longer a concern.
+ */
 void
 zfs_dbgmsg_init(void)
 {
-	list_create(&zfs_dbgmsgs, sizeof (zfs_dbgmsg_t),
-	    offsetof(zfs_dbgmsg_t, zdm_node));
-	mutex_init(&zfs_dbgmsgs_lock, NULL, MUTEX_DEFAULT, NULL);
+	if (zfs_flags == 0) {
+#if defined(_KERNEL)
+		zfs_flags = ZFS_DEBUG_DPRINTF;
+		spl_debug_mask |= SD_DPRINTF;
+		spl_debug_subsys |= SS_USER1;
+#else
+		zfs_flags = ~ZFS_DEBUG_DPRINTF;
+#endif /* _KERNEL */
+	}
 }
 
 void
 zfs_dbgmsg_fini(void)
 {
-	zfs_dbgmsg_t *zdm;
-
-	while ((zdm = list_remove_head(&zfs_dbgmsgs)) != NULL) {
-		int size = sizeof (zfs_dbgmsg_t) + strlen(zdm->zdm_msg);
-		kmem_free(zdm, size);
-		zfs_dbgmsg_size -= size;
-	}
-	mutex_destroy(&zfs_dbgmsgs_lock);
-	ASSERT3U(zfs_dbgmsg_size, ==, 0);
+	return;
 }
 
-/*
- * Print these messages by running:
- * 	echo ::zfs_dbgmsg | mdb -k
- *
- * Monitor these messages by running:
- * 	dtrace -q -n 'zfs-dbgmsg{printf("%s\n", stringof(arg0))}'
- */
-void
-zfs_dbgmsg(const char *fmt, ...)
-{
-	int size;
-	va_list adx;
-	zfs_dbgmsg_t *zdm;
 
-	va_start(adx, fmt);
-	size = vsnprintf(NULL, 0, fmt, adx);
-	va_end(adx);
+#if defined(_KERNEL)
+module_param(zfs_flags, int, 0644);
+MODULE_PARM_DESC(zfs_flags, "Set additional debugging flags");
 
-	/*
-	 * There is one byte of string in sizeof (zfs_dbgmsg_t), used
-	 * for the terminating null.
-	 */
-	zdm = kmem_alloc(sizeof (zfs_dbgmsg_t) + size, KM_SLEEP);
-	zdm->zdm_timestamp = gethrestime_sec();
-
-	va_start(adx, fmt);
-	(void) vsnprintf(zdm->zdm_msg, size + 1, fmt, adx);
-	va_end(adx);
-
-	DTRACE_PROBE1(zfs__dbgmsg, char *, zdm->zdm_msg);
-
-	mutex_enter(&zfs_dbgmsgs_lock);
-	list_insert_tail(&zfs_dbgmsgs, zdm);
-	zfs_dbgmsg_size += sizeof (zfs_dbgmsg_t) + size;
-	while (zfs_dbgmsg_size > zfs_dbgmsg_maxsize) {
-		zdm = list_remove_head(&zfs_dbgmsgs);
-		size = sizeof (zfs_dbgmsg_t) + strlen(zdm->zdm_msg);
-		kmem_free(zdm, size);
-		zfs_dbgmsg_size -= size;
-	}
-	mutex_exit(&zfs_dbgmsgs_lock);
-}
+module_param(zfs_recover, int, 0644);
+MODULE_PARM_DESC(zfs_recover, "Set to attempt to recover from fatal errors");
+#endif /* _KERNEL */
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index c8ff0359553c..532f17aa16af 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -119,42 +119,6 @@ static int zfs_fill_zplprops_root(uint64_t, nvlist_t *, nvlist_t *,
     boolean_t *);
 int zfs_set_prop_nvlist(const char *, zprop_source_t, nvlist_t *, nvlist_t **);
 
-/* _NOTE(PRINTFLIKE(4)) - this is printf-like, but lint is too whiney */
-void
-__dprintf(const char *file, const char *func, int line, const char *fmt, ...)
-{
-	const char *newfile;
-	char buf[512];
-	va_list adx;
-
-	/*
-	 * Get rid of annoying "../common/" prefix to filename.
-	 */
-	newfile = strrchr(file, '/');
-	if (newfile != NULL) {
-		newfile = newfile + 1; /* Get rid of leading / */
-	} else {
-		newfile = file;
-	}
-
-	va_start(adx, fmt);
-	(void) vsnprintf(buf, sizeof (buf), fmt, adx);
-	va_end(adx);
-
-	/*
-	 * To get this data, use the zfs-dprintf probe as so:
-	 * dtrace -q -n 'zfs-dprintf \
-	 *	/stringof(arg0) == "dbuf.c"/ \
-	 *	{printf("%s: %s", stringof(arg1), stringof(arg3))}'
-	 * arg0 = file name
-	 * arg1 = function name
-	 * arg2 = line number
-	 * arg3 = message
-	 */
-	DTRACE_PROBE4(zfs__dprintf,
-	    char *, newfile, char *, func, int, line, char *, buf);
-}
-
 static void
 history_str_free(char *buf)
 {