tracing, perf_counter: Add help text to CONFIG_EVENT_PROFILE

Explain what tracepoint profiling sources are about.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: NJeff Garzik <jeff@garzik.org>
LKML-Reference: <1248856508.6987.3041.camel@twins>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

init/Kconfig

@@ -961,9 +961,17 @@ config PERF_COUNTERS
 	  Say Y if unsure.
 
 config EVENT_PROFILE
-	bool "Tracepoint profile sources"
+	bool "Tracepoint profiling sources"
 	depends on PERF_COUNTERS && EVENT_TRACING
 	default y
+	help
+	 Allow the use of tracepoints as software performance counters.
+
+	 When this is enabled, you can create perf counters based on
+	 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
+	 found in debugfs://tracing/events/*/*/id. (The -e/--events
+	 option to the perf tool can parse and interpret symbolic
+	 tracepoints, in the subsystem:tracepoint_name format.)
 
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