Commit f689e4f2 authored by Yordan Karadzhov (VMware)'s avatar Yordan Karadzhov (VMware) Committed by Steven Rostedt (VMware)
Browse files

tracing: Define new ftrace event "func_repeats" 

The event aims to consolidate the function tracing record in the cases
when a single function is called number of times consecutively.

	while (cond)
		do_func();

This may happen in various scenarios (busy waiting for example).
The new ftrace event can be used to show repeated function events with
a single event and save space on the ring buffer

Link: https://lkml.kernel.org/r/20210415181854.147448-3-y.karadz@gmail.com



Signed-off-by: default avatarYordan Karadzhov (VMware) <y.karadz@gmail.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent eaa7a897

kernel/trace/trace.h

+3 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ enum trace_type { 
	TRACE_BPUTS,

	TRACE_HWLAT,

	TRACE_RAW_DATA,

	TRACE_FUNC_REPEATS,



	__TRACE_LAST_TYPE,

};
@@ -442,6 +443,8 @@ extern void __ftrace_bad_type(void); 
			  TRACE_GRAPH_ENT);		\

		IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry,	\

			  TRACE_GRAPH_RET);		\

		IF_ASSIGN(var, ent, struct func_repeats_entry,		\

			  TRACE_FUNC_REPEATS);				\

		__ftrace_bad_type();					\

	} while (0)

kernel/trace/trace_entries.h

+22 −0
Original line number Diff line number Diff line
@@ -338,3 +338,25 @@ FTRACE_ENTRY(hwlat, hwlat_entry, 
		 __entry->nmi_total_ts,

		 __entry->nmi_count)

);



#define FUNC_REPEATS_GET_DELTA_TS(entry)				\

	(((u64)(entry)->top_delta_ts << 32) | (entry)->bottom_delta_ts)	\



FTRACE_ENTRY(func_repeats, func_repeats_entry,



	TRACE_FUNC_REPEATS,



	F_STRUCT(

		__field(	unsigned long,	ip		)

		__field(	unsigned long,	parent_ip	)

		__field(	u16	,	count		)

		__field(	u16	,	top_delta_ts	)

		__field(	u32	,	bottom_delta_ts	)

	),



	F_printk(" %ps <-%ps\t(repeats:%u  delta: -%llu)",

		 (void *)__entry->ip,

		 (void *)__entry->parent_ip,

		 __entry->count,

		 FUNC_REPEATS_GET_DELTA_TS(__entry))

);

kernel/trace/trace_output.c

+48 −0
Original line number Diff line number Diff line
@@ -1381,6 +1381,53 @@ static struct trace_event trace_raw_data_event = { 
	.funcs		= &trace_raw_data_funcs,

};



static enum print_line_t

trace_func_repeats_raw(struct trace_iterator *iter, int flags,

			 struct trace_event *event)

{

	struct func_repeats_entry *field;

	struct trace_seq *s = &iter->seq;



	trace_assign_type(field, iter->ent);



	trace_seq_printf(s, "%lu %lu %u %llu\n",

			 field->ip,

			 field->parent_ip,

			 field->count,

			 FUNC_REPEATS_GET_DELTA_TS(field));



	return trace_handle_return(s);

}



static enum print_line_t

trace_func_repeats_print(struct trace_iterator *iter, int flags,

			 struct trace_event *event)

{

	struct func_repeats_entry *field;

	struct trace_seq *s = &iter->seq;



	trace_assign_type(field, iter->ent);



	seq_print_ip_sym(s, field->ip, flags);

	trace_seq_puts(s, " <-");

	seq_print_ip_sym(s, field->parent_ip, flags);

	trace_seq_printf(s, " (repeats: %u, last_ts:", field->count);

	trace_print_time(s, iter,

			 iter->ts - FUNC_REPEATS_GET_DELTA_TS(field));

	trace_seq_puts(s, ")\n");



	return trace_handle_return(s);

}



static struct trace_event_functions trace_func_repeats_funcs = {

	.trace		= trace_func_repeats_print,

	.raw		= trace_func_repeats_raw,

};



static struct trace_event trace_func_repeats_event = {

	.type	 	= TRACE_FUNC_REPEATS,

	.funcs		= &trace_func_repeats_funcs,

};



static struct trace_event *events[] __initdata = {

	&trace_fn_event,
@@ -1393,6 +1440,7 @@ static struct trace_event *events[] __initdata = { 
	&trace_print_event,

	&trace_hwlat_event,

	&trace_raw_data_event,

	&trace_func_repeats_event,

	NULL

};