diff options
author | Ingo Molnar <mingo@kernel.org> | 2013-02-28 10:12:04 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2013-02-28 10:12:04 +0100 |
commit | a335358f52aec4397594043ac799d15f92e728dd (patch) | |
tree | 8146f2c71be7a05ef1615a431adecd9ec46d3e2f | |
parent | ff1fb5f6b4925a536ffb8171e5f2dbd01ccfeb97 (diff) | |
parent | db05021d49a994ee40a9735d9c3cb0060c9babb8 (diff) | |
download | linux-stable-a335358f52aec4397594043ac799d15f92e728dd.tar.gz linux-stable-a335358f52aec4397594043ac799d15f92e728dd.tar.bz2 linux-stable-a335358f52aec4397594043ac799d15f92e728dd.zip |
Merge branch 'tip/perf/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into perf/urgent
Pull an ftrace Kconfig help text fix from Steve Rostedt.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r-- | kernel/trace/Kconfig | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 36567564e221..b516a8e19d51 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -429,24 +429,28 @@ config PROBE_EVENTS def_bool n config DYNAMIC_FTRACE - bool "enable/disable ftrace tracepoints dynamically" + bool "enable/disable function tracing dynamically" depends on FUNCTION_TRACER depends on HAVE_DYNAMIC_FTRACE default y help - This option will modify all the calls to ftrace dynamically - (will patch them out of the binary image and replace them - with a No-Op instruction) as they are called. A table is - created to dynamically enable them again. + This option will modify all the calls to function tracing + dynamically (will patch them out of the binary image and + replace them with a No-Op instruction) on boot up. During + compile time, a table is made of all the locations that ftrace + can function trace, and this table is linked into the kernel + image. When this is enabled, functions can be individually + enabled, and the functions not enabled will not affect + performance of the system. + + See the files in /sys/kernel/debug/tracing: + available_filter_functions + set_ftrace_filter + set_ftrace_notrace This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but otherwise has native performance as long as no tracing is active. - The changes to the code are done by a kernel thread that - wakes up once a second and checks to see if any ftrace calls - were made. If so, it runs stop_machine (stops all CPUS) - and modifies the code to jump over the call to ftrace. - config DYNAMIC_FTRACE_WITH_REGS def_bool y depends on DYNAMIC_FTRACE |