tracing: move function profiler data out of function struct

Impact: reduce size of memory in function profiler

The function profiler originally introduces its counters into the
function records itself. There is 20 thousand different functions on
a normal system, and that is adding 20 thousand counters for profiling
event when not needed.

A normal run of the profiler yields only a couple of thousand functions
executed, depending on what is being profiled. This means we have around
18 thousand useless counters.

This patch rectifies this by moving the data out of the function
records used by dynamic ftrace. Data is preallocated to hold the functions
when the profiling begins. Checks are made during profiling to see if
more recorcds should be allocated, and they are allocated if it is safe
to do so.

This also removes the dependency from using dynamic ftrace, and also
removes the overhead by having it enabled.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 95e9ad5735d9..8a4136096d7d 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -379,20 +379,16 @@ config DYNAMIC_FTRACE
 
 config FUNCTION_PROFILER
         bool "Kernel function profiler"
-        depends on DYNAMIC_FTRACE
+        depends on FUNCTION_TRACER
         default n
         help
-         This option enables the kernel function profiler. When the dynamic
-         function tracing is enabled, a counter is added into the function
-         records used by the dynamic function tracer. A file is created in
-         debugfs called function_profile_enabled which defaults to zero.
+         This option enables the kernel function profiler. A file is created
+         in debugfs called function_profile_enabled which defaults to zero.
          When a 1 is echoed into this file profiling begins, and when a
          zero is entered, profiling stops. A file in the trace_stats
          directory called functions, that show the list of functions that
          have been hit and their counters.
 
-         This takes up around 320K more memory.
-
          If in doubt, say N
 
 config FTRACE_MCOUNT_RECORD