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

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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: Robert Elliott <elliott@hp.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Robert Elliott 2014-05-20 17:10:51 -05:00 committed by Steven Rostedt
parent ccdb594653
commit 607e3a2920
3 changed files with 33 additions and 3 deletions
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26
Documentation/trace/ftrace.txt
View File

@ -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

1
kernel/trace/trace.h
View File

@ -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)

9
kernel/trace/trace_functions_graph.c
View File

@ -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;