perf script: Extend misc field decoding with switch out event type

Append 'p' sign to 'S' tag designating the type of context switch out event so
'Sp' means preemption context switch. Documentation is extended to cover
new presentation changes.

$ perf script --show-switch-events -F +misc -I -i perf.data:

hdparm 4073 [004] U 762.198265: 380194 cycles:ppp: 7faf727f5a23 strchr (/usr/lib64/ld-2.26.so)
hdparm 4073 [004] K 762.198366: 441572 cycles:ppp: ffffffffb9218435 alloc_set_pte (/lib/modules/4.16.0-rc6+/build/vmlinux)
hdparm 4073 [004] S 762.198391: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [004] 762.198392: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 4073/4073
swapper 0 [004] Sp 762.198477: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 4073/4073
hdparm 4073 [004] 762.198478: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
swapper 0 [007] K 762.198514: 2303073 cycles:ppp: ffffffffb98b0c66 intel_idle (/lib/modules/4.16.0-rc6+/build/vmlinux)
swapper 0 [007] Sp 762.198561: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 1134/1134
kworker/u16:18 1134 [007] 762.198562: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
kworker/u16:18 1134 [007] S 762.198567: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0

Signed-off-by: Alexey Budankov <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-script.txt

···
 	For sample events it's possible to display misc field with -F +misc option,
 	following letters are displayed for each bit:
 
-	  PERF_RECORD_MISC_KERNEL        K
-	  PERF_RECORD_MISC_USER          U
-	  PERF_RECORD_MISC_HYPERVISOR    H
-	  PERF_RECORD_MISC_GUEST_KERNEL  G
-	  PERF_RECORD_MISC_GUEST_USER    g
-	  PERF_RECORD_MISC_MMAP_DATA*    M
-	  PERF_RECORD_MISC_COMM_EXEC     E
-	  PERF_RECORD_MISC_SWITCH_OUT    S
+	  PERF_RECORD_MISC_KERNEL               K
+	  PERF_RECORD_MISC_USER                 U
+	  PERF_RECORD_MISC_HYPERVISOR           H
+	  PERF_RECORD_MISC_GUEST_KERNEL         G
+	  PERF_RECORD_MISC_GUEST_USER           g
+	  PERF_RECORD_MISC_MMAP_DATA*           M
+	  PERF_RECORD_MISC_COMM_EXEC            E
+	  PERF_RECORD_MISC_SWITCH_OUT           S
+	  PERF_RECORD_MISC_SWITCH_OUT_PREEMPT   Sp
 
 	  $ perf script -F +misc ...
 	   sched-messaging  1414 K     28690.636582:       4590 cycles ...

tools/perf/builtin-script.c

···
 			break;
 		case PERF_RECORD_SWITCH:
 		case PERF_RECORD_SWITCH_CPU_WIDE:
-			if (has(SWITCH_OUT))
+			if (has(SWITCH_OUT)) {
 				ret += fprintf(fp, "S");
+				if (sample->misc & PERF_RECORD_MISC_SWITCH_OUT_PREEMPT)
+					ret += fprintf(fp, "p");
+			}
 		default:
 			break;
 		}