diff options
| author | Tim Bird <tim.bird@am.sony.com> | 2010-02-25 15:36:43 -0800 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2010-03-05 21:20:57 -0500 |
| commit | 0e95017355dcf43031da6d0e360a748717e56df1 (patch) | |
| tree | 829989bfb494e8d2d773d9dc1bc014b7f28d3bed /kernel/trace/trace.h | |
| parent | 1acaa1b2d9b5904c9cce06122990a2d71046ce16 (diff) | |
function-graph: Add tracing_thresh support to function_graph tracer
Add support for tracing_thresh to the function_graph tracer. This
version of this feature isolates the checks into new entry and
return functions, to avoid adding more conditional code into the
main function_graph paths.
When the tracing_thresh is set and the function graph tracer is
enabled, only the functions that took longer than the time in
microseconds that was set in tracing_thresh are recorded. To do this
efficiently, only the function exits are recorded:
[tracing]# echo 100 > tracing_thresh
[tracing]# echo function_graph > current_tracer
[tracing]# cat trace
# tracer: function_graph
#
# CPU DURATION FUNCTION CALLS
# | | | | | | |
1) ! 119.214 us | } /* smp_apic_timer_interrupt */
1) <========== |
0) ! 101.527 us | } /* __rcu_process_callbacks */
0) ! 126.461 us | } /* rcu_process_callbacks */
0) ! 145.111 us | } /* __do_softirq */
0) ! 149.667 us | } /* do_softirq */
0) ! 168.817 us | } /* irq_exit */
0) ! 248.254 us | } /* smp_apic_timer_interrupt */
Also, add support for specifying tracing_thresh on the kernel
command line. When used like so: "tracing_thresh=200 ftrace=function_graph"
this can be used to analyse system startup. It is important to disable
tracing soon after boot, in order to avoid losing the trace data.
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Tim Bird <tim.bird@am.sony.com>
LKML-Reference: <4B87098B.4040308@am.sony.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace.h')
| -rw-r--r-- | kernel/trace/trace.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index fd05bcaf91b0..1bc8cd1431d7 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -396,9 +396,10 @@ extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr); extern unsigned long nsecs_to_usecs(unsigned long nsecs); +extern unsigned long tracing_thresh; + #ifdef CONFIG_TRACER_MAX_TRACE extern unsigned long tracing_max_latency; -extern unsigned long tracing_thresh; void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu); void update_max_tr_single(struct trace_array *tr, |