15 	 *    perf stat -e "{instructions,topdown-retiring,slots}" -C0 sleep 1  in arch_evlist__cmp()
18 	 *          15,066,240     slots  in arch_evlist__cmp()
22 	 *    perf stat -e "instructions,topdown-retiring,slots" -C0 sleep 1  in arch_evlist__cmp()
26 	 *          17,108,370     slots  in arch_evlist__cmp()
28 	 * c. slots event in a group but topdown metrics events outside the group  in arch_evlist__cmp()
29 	 *    perf stat -e "{instructions,slots},topdown-retiring" -C0 sleep 1  in arch_evlist__cmp()
32 	 *         20,323,878      slots  in arch_evlist__cmp()
35 	 * d. slots event and topdown metrics events in two groups  in arch_evlist__cmp()
36 	 *    perf stat -e "{instructions,slots},{topdown-retiring}" -C0 sleep 1  in arch_evlist__cmp()
39 	 *         26,319,024      slots  in arch_evlist__cmp()
42 	 * e. slots event and metrics event are not in a group and not adjacent  in arch_evlist__cmp()
43 	 *    perf stat -e "{instructions,slots},cycles,topdown-retiring" -C0 sleep 1  in arch_evlist__cmp()
45 	 *         68,433,522      slots  in arch_evlist__cmp()
52 		/* Ensure the topdown slots comes first. */  in arch_evlist__cmp()
60 		 * events are not in same group with previous slots event. If  in arch_evlist__cmp()
61 		 * topdown metrics events are already in same group with slots  in arch_evlist__cmp()
95 			/* Slots event already present, nothing to do. */  in arch_evlist__add_required_events()