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-rw-r--r--init/Kconfig37
1 files changed, 27 insertions, 10 deletions
diff --git a/init/Kconfig b/init/Kconfig
index cfdf5c3..706728b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -920,26 +920,31 @@ config HAVE_PERF_EVENTS
help
See tools/perf/design.txt for details.
-menu "Performance Counters"
+menu "Kernel Performance Events And Counters"
config PERF_EVENTS
- bool "Kernel Performance Counters"
- default y if PROFILING
+ bool "Kernel performance events and counters"
+ default y if (PROFILING || PERF_COUNTERS)
depends on HAVE_PERF_EVENTS
select ANON_INODES
help
- Enable kernel support for performance counter hardware.
+ Enable kernel support for various performance events provided
+ by software and hardware.
- Performance counters are special hardware registers available
- on most modern CPUs. These registers count the number of certain
+ Software events are supported either build-in or via the
+ use of generic tracepoints.
+
+ Most modern CPUs support performance events via performance
+ counter registers. These registers count the number of certain
types of hw events: such as instructions executed, cachemisses
suffered, or branches mis-predicted - without slowing down the
kernel or applications. These registers can also trigger interrupts
when a threshold number of events have passed - and can thus be
used to profile the code that runs on that CPU.
- The Linux Performance Counter subsystem provides an abstraction of
- these hardware capabilities, available via a system call. It
+ The Linux Performance Event subsystem provides an abstraction of
+ these software and hardware cevent apabilities, available via a
+ system call and used by the "perf" utility in tools/perf/. It
provides per task and per CPU counters, and it provides event
capabilities on top of those.
@@ -950,14 +955,26 @@ config EVENT_PROFILE
depends on PERF_EVENTS && EVENT_TRACING
default y
help
- Allow the use of tracepoints as software performance counters.
+ Allow the use of tracepoints as software performance events.
- When this is enabled, you can create perf counters based on
+ When this is enabled, you can create perf events 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.)
+config PERF_COUNTERS
+ bool "Kernel performance counters (old config option)"
+ depends on HAVE_PERF_EVENTS
+ help
+ This config has been obsoleted by the PERF_EVENTS
+ config option - please see that one for details.
+
+ It has no effect on the kernel whether you enable
+ it or not, it is a compatibility placeholder.
+
+ Say N if unsure.
+
endmenu
config VM_EVENT_COUNTERS
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