+ u64 *ts_end; /*
+ * timestamp_end per sub-buffer.
+ * Time is sampled by the
+ * switch_*_end() callbacks which
+ * are the last space reservation
+ * performed in the sub-buffer
+ * before it can be fully
+ * committed and delivered. This
+ * time value is then read by
+ * the deliver callback,
+ * performed by the last commit
+ * before the buffer becomes
+ * readable.
+ */