Commit a312a0f7 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
Browse files

fgraph: Use fgraph data to store subtime for profiler 

Instead of having the "subtime" for the function profiler in the
infrastructure ftrace_ret_stack structure, have it use the fgraph data
reserve and retrieve functions.

This will keep the limited shadow stack from wasting 8 bytes for something
that is seldom used.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Link: https://lore.kernel.org/20240914214826.780323141@goodmis.org


Acked-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent a370b72e

include/linux/ftrace.h

+1 −3
Original line number Diff line number Diff line
@@ -1081,6 +1081,7 @@ struct fgraph_ops { 


void *fgraph_reserve_data(int idx, int size_bytes);

void *fgraph_retrieve_data(int idx, int *size_bytes);

void *fgraph_retrieve_parent_data(int idx, int *size_bytes, int depth);



/*

 * Stack of return addresses for functions
@@ -1091,9 +1092,6 @@ struct ftrace_ret_stack { 
	unsigned long ret;

	unsigned long func;

	unsigned long long calltime;

#ifdef CONFIG_FUNCTION_PROFILER

	unsigned long long subtime;

#endif

#ifdef HAVE_FUNCTION_GRAPH_FP_TEST

	unsigned long fp;

#endif

kernel/trace/fgraph.c

+49 −15
Original line number Diff line number Diff line
@@ -390,21 +390,7 @@ void *fgraph_reserve_data(int idx, int size_bytes) 
 */

void *fgraph_retrieve_data(int idx, int *size_bytes)

{

	int offset = current->curr_ret_stack - 1;

	unsigned long val;



	val = get_fgraph_entry(current, offset);

	while (__get_type(val) == FGRAPH_TYPE_DATA) {

		if (__get_data_index(val) == idx)

			goto found;

		offset -= __get_data_size(val) + 1;

		val = get_fgraph_entry(current, offset);

	}

	return NULL;

found:

	if (size_bytes)

		*size_bytes = __get_data_size(val) * sizeof(long);

	return get_data_type_data(current, offset);

	return fgraph_retrieve_parent_data(idx, size_bytes, 0);

}



/**
@@ -460,6 +446,54 @@ get_ret_stack(struct task_struct *t, int offset, int *frame_offset) 
	return RET_STACK(t, offset);

}



/**

 * fgraph_retrieve_parent_data - get data from a parent function

 * @idx: The index into the fgraph_array (fgraph_ops::idx)

 * @size_bytes: A pointer to retrieved data size

 * @depth: The depth to find the parent (0 is the current function)

 *

 * This is similar to fgraph_retrieve_data() but can be used to retrieve

 * data from a parent caller function.

 *

 * Return: a pointer to the specified parent data or NULL if not found

 */

void *fgraph_retrieve_parent_data(int idx, int *size_bytes, int depth)

{

	struct ftrace_ret_stack *ret_stack = NULL;

	int offset = current->curr_ret_stack;

	unsigned long val;



	if (offset <= 0)

		return NULL;



	for (;;) {

		int next_offset;



		ret_stack = get_ret_stack(current, offset, &next_offset);

		if (!ret_stack || --depth < 0)

			break;

		offset = next_offset;

	}



	if (!ret_stack)

		return NULL;



	offset--;



	val = get_fgraph_entry(current, offset);

	while (__get_type(val) == FGRAPH_TYPE_DATA) {

		if (__get_data_index(val) == idx)

			goto found;

		offset -= __get_data_size(val) + 1;

		val = get_fgraph_entry(current, offset);

	}

	return NULL;

found:

	if (size_bytes)

		*size_bytes = __get_data_size(val) * sizeof(long);

	return get_data_type_data(current, offset);

}



/* Both enabled by default (can be cleared by function_graph tracer flags */

static bool fgraph_sleep_time = true;

kernel/trace/ftrace.c

+12 −11
Original line number Diff line number Diff line
@@ -823,7 +823,7 @@ void ftrace_graph_graph_time_control(bool enable) 
static int profile_graph_entry(struct ftrace_graph_ent *trace,

			       struct fgraph_ops *gops)

{

	struct ftrace_ret_stack *ret_stack;

	unsigned long long *subtime;



	function_profile_call(trace->func, 0, NULL, NULL);
@@ -831,9 +831,9 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace, 
	if (!current->ret_stack)

		return 0;



	ret_stack = ftrace_graph_get_ret_stack(current, 0);

	if (ret_stack)

		ret_stack->subtime = 0;

	subtime = fgraph_reserve_data(gops->idx, sizeof(*subtime));

	if (subtime)

		*subtime = 0;



	return 1;

}
@@ -841,11 +841,12 @@ static int profile_graph_entry(struct ftrace_graph_ent *trace, 
static void profile_graph_return(struct ftrace_graph_ret *trace,

				 struct fgraph_ops *gops)

{

	struct ftrace_ret_stack *ret_stack;

	struct ftrace_profile_stat *stat;

	unsigned long long calltime;

	unsigned long long *subtime;

	struct ftrace_profile *rec;

	unsigned long flags;

	int size;



	local_irq_save(flags);

	stat = this_cpu_ptr(&ftrace_profile_stats);
@@ -861,13 +862,13 @@ static void profile_graph_return(struct ftrace_graph_ret *trace, 
	if (!fgraph_graph_time) {



		/* Append this call time to the parent time to subtract */

		ret_stack = ftrace_graph_get_ret_stack(current, 1);

		if (ret_stack)

			ret_stack->subtime += calltime;

		subtime = fgraph_retrieve_parent_data(gops->idx, &size, 1);

		if (subtime)

			*subtime += calltime;



		ret_stack = ftrace_graph_get_ret_stack(current, 0);

		if (ret_stack && ret_stack->subtime < calltime)

			calltime -= ret_stack->subtime;

		subtime = fgraph_retrieve_data(gops->idx, &size);

		if (subtime && *subtime && *subtime < calltime)

			calltime -= *subtime;

		else

			calltime = 0;

	}