Commit 607e3a29 authored by Robert Elliott's avatar Robert Elliott Committed by Steven Rostedt
Browse files

tracing: Add funcgraph_tail option to print function name after closing braces 

In the function-graph tracer, add a funcgraph_tail option
to print the function name on all } lines, not just
functions whose first line is no longer in the trace
buffer.

If a function calls other traced functions, its total
time appears on its } line.  This change allows grep
to be used to determine the function for which the
line corresponds.

Update Documentation/trace/ftrace.txt to describe
this new option.

Link: http://lkml.kernel.org/p/20140520221041.8359.6782.stgit@beardog.cce.hp.com



Signed-off-by: default avatarRobert Elliott <elliott@hp.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent ccdb5946

Documentation/trace/ftrace.txt

+26 −0
Original line number Diff line number Diff line
@@ -2003,6 +2003,32 @@ want, depending on your needs. 
  360.774530 |   1)   0.594 us    |                                          __phys_addr();





The function name is always displayed after the closing bracket

for a function if the start of that function is not in the

trace buffer.



Display of the function name after the closing bracket may be

enabled for functions whose start is in the trace buffer,

allowing easier searching with grep for function durations.

It is default disabled.



	hide: echo nofuncgraph-tail > trace_options

	show: echo funcgraph-tail > trace_options



  Example with nofuncgraph-tail (default):

  0)               |      putname() {

  0)               |        kmem_cache_free() {

  0)   0.518 us    |          __phys_addr();

  0)   1.757 us    |        }

  0)   2.861 us    |      }



  Example with funcgraph-tail:

  0)               |      putname() {

  0)               |        kmem_cache_free() {

  0)   0.518 us    |          __phys_addr();

  0)   1.757 us    |        } /* kmem_cache_free() */

  0)   2.861 us    |      } /* putname() */



You can put some comments on specific functions by using

trace_printk() For example, if you want to put a comment inside

the __might_sleep() function, you just have to include

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -725,6 +725,7 @@ extern unsigned long trace_flags; 
#define TRACE_GRAPH_PRINT_DURATION      0x10

#define TRACE_GRAPH_PRINT_ABS_TIME      0x20

#define TRACE_GRAPH_PRINT_IRQS          0x40

#define TRACE_GRAPH_PRINT_TAIL          0x80

#define TRACE_GRAPH_PRINT_FILL_SHIFT	28

#define TRACE_GRAPH_PRINT_FILL_MASK	(0x3 << TRACE_GRAPH_PRINT_FILL_SHIFT)

kernel/trace/trace_functions_graph.c

+6 −3
Original line number Diff line number Diff line
@@ -55,11 +55,13 @@ static struct tracer_opt trace_opts[] = { 
	{ TRACER_OPT(funcgraph-abstime, TRACE_GRAPH_PRINT_ABS_TIME) },

	/* Display interrupts */

	{ TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) },

	/* Display function name after trailing } */

	{ TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) },

	{ } /* Empty entry */

};



static struct tracer_flags tracer_flags = {

	/* Don't display overruns and proc by default */

	/* Don't display overruns, proc, or tail by default */

	.val = TRACE_GRAPH_PRINT_CPU | TRACE_GRAPH_PRINT_OVERHEAD |

	       TRACE_GRAPH_PRINT_DURATION | TRACE_GRAPH_PRINT_IRQS,

	.opts = trace_opts
@@ -1167,9 +1169,10 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s, 
	 * If the return function does not have a matching entry,

	 * then the entry was lost. Instead of just printing

	 * the '}' and letting the user guess what function this

	 * belongs to, write out the function name.

	 * belongs to, write out the function name. Always do

	 * that if the funcgraph-tail option is enabled.

	 */

	if (func_match) {

	if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL)) {

		ret = trace_seq_puts(s, "}\n");

		if (!ret)

			return TRACE_TYPE_PARTIAL_LINE;

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