-#define DEFAULT_CHANNEL_SUBBUF_NUM 8
-#define DEFAULT_CHANNEL_SWITCH_TIMER 0 /* usec */
-#define DEFAULT_CHANNEL_READ_TIMER 200 /* usec */
-/* See lttng.h enum lttng_kernel_output for channel output */
-#define DEFAULT_KERNEL_CHANNEL_OUTPUT LTTNG_KERNEL_SPLICE
+#define DEFAULT_CHANNEL_SUBBUF_NUM 8
+#define DEFAULT_CHANNEL_SWITCH_TIMER 0 /* usec */
+#define DEFAULT_CHANNEL_READ_TIMER 200 /* usec */
+#define DEFAULT_CHANNEL_OUTPUT LTTNG_EVENT_MMAP
+
+#define DEFAULT_METADATA_SUBBUF_SIZE 4096
+#define DEFAULT_METADATA_SUBBUF_NUM 2
+
+/* Kernel has different defaults */
+
+/* DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE must always be a power of 2 */
+#define DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE 262144 /* bytes */
+/* DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM must always be a power of 2 */
+#define DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM 4
+/* See lttng-kernel.h enum lttng_kernel_output for channel output */
+#define DEFAULT_KERNEL_CHANNEL_OUTPUT LTTNG_EVENT_SPLICE
+
+/* User space defaults */
+
+/* Must be a power of 2 */
+#define DEFAULT_UST_CHANNEL_SUBBUF_SIZE 4096 /* bytes */
+/* Must be a power of 2 */
+#define DEFAULT_UST_CHANNEL_SUBBUF_NUM 4
+/* See lttng-ust.h enum lttng_ust_output */