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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-03-11 07:54:29 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-03-11 07:54:29 -0700 |
| commit | 7c6baa304b841673d3a55ea4fcf9a5cbf7a1674b (patch) | |
| tree | a6f9970cebfb573a74a4abd06ff9caee41460e9a /kernel/trace/Kconfig | |
| parent | 0cb77508252e2d0e00c5ec7e57b4be9b3f7eb24d (diff) | |
| parent | cb16b91a449afd01b85ec4e59f30449d11c4acd7 (diff) | |
| download | linux-7c6baa304b841673d3a55ea4fcf9a5cbf7a1674b.tar.bz2 | |
Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar:
"Misc minor fixes mostly related to tracing"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
s390: Fix a header dependencies related build error
tracing: update documentation of snapshot utility
tracing: Do not return EINVAL in snapshot when not allocated
tracing: Add help of snapshot feature when snapshot is empty
ftrace: Update the kconfig for DYNAMIC_FTRACE
Diffstat (limited to 'kernel/trace/Kconfig')
| -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 192473b22799..fc382d6e2765 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -414,24 +414,28 @@ 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 |