Commit 067fe038 authored by Tom Zanussi's avatar Tom Zanussi Committed by Steven Rostedt (VMware)
Browse files

tracing: Add variable reference handling to hist triggers 

Add the necessary infrastructure to allow the variables defined on one
event to be referenced in another.  This allows variables set by a
previous event to be referenced and used in expressions combining the
variable values saved by that previous event and the event fields of
the current event.  For example, here's how a latency can be
calculated and saved into yet another variable named 'wakeup_lat':

    # echo 'hist:keys=pid,prio:ts0=common_timestamp ...
    # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp-$ts0 ...

In the first event, the event's timetamp is saved into the variable
ts0.  In the next line, ts0 is subtracted from the second event's
timestamp to produce the latency.

Further users of variable references will be described in subsequent
patches, such as for instance how the 'wakeup_lat' variable above can
be displayed in a latency histogram.

Link: http://lkml.kernel.org/r/b1d3e6975374e34d501ff417c20189c3f9b2c7b8.1516069914.git.tom.zanussi@linux.intel.com



Signed-off-by: default avatarTom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 19a9facd

kernel/trace/trace.c

+2 −0
Original line number Diff line number Diff line
@@ -7783,6 +7783,7 @@ static int instance_mkdir(const char *name) 


	INIT_LIST_HEAD(&tr->systems);

	INIT_LIST_HEAD(&tr->events);

	INIT_LIST_HEAD(&tr->hist_vars);



	if (allocate_trace_buffers(tr, trace_buf_size) < 0)

		goto out_free_tr;
@@ -8533,6 +8534,7 @@ __init static int tracer_alloc_buffers(void) 


	INIT_LIST_HEAD(&global_trace.systems);

	INIT_LIST_HEAD(&global_trace.events);

	INIT_LIST_HEAD(&global_trace.hist_vars);

	list_add(&global_trace.list, &ftrace_trace_arrays);



	apply_trace_boot_options();

kernel/trace/trace.h

+3 −0
Original line number Diff line number Diff line
@@ -274,6 +274,7 @@ struct trace_array { 
	int			function_enabled;

#endif

	int			time_stamp_abs_ref;

	struct list_head	hist_vars;

};



enum {
@@ -1548,6 +1549,8 @@ extern void pause_named_trigger(struct event_trigger_data *data); 
extern void unpause_named_trigger(struct event_trigger_data *data);

extern void set_named_trigger_data(struct event_trigger_data *data,

				   struct event_trigger_data *named_data);

extern struct event_trigger_data *

get_named_trigger_data(struct event_trigger_data *data);

extern int register_event_command(struct event_command *cmd);

extern int unregister_event_command(struct event_command *cmd);

extern int register_trigger_hist_enable_disable_cmds(void);

kernel/trace/trace_events_hist.c

+645 −16

File changed.

Preview size limit exceeded, changes collapsed.

kernel/trace/trace_events_trigger.c

+6 −0
Original line number Diff line number Diff line
@@ -909,6 +909,12 @@ void set_named_trigger_data(struct event_trigger_data *data, 
	data->named_data = named_data;

}



struct event_trigger_data *

get_named_trigger_data(struct event_trigger_data *data)

{

	return data->named_data;

}



static void

traceon_trigger(struct event_trigger_data *data, void *rec,

		struct ring_buffer_event *event)

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