Commit 15e6cb36 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

tracing: add a tracer to catch execution time of kernel functions 



Impact: add new tracing plugin which can trace full (entry+exit) function calls

This tracer uses the low level function return ftrace plugin to
measure the execution time of the kernel functions.

The first field is the caller of the function, the second is the
measured function, and the last one is the execution time in
nanoseconds.

- v3:

- HAVE_FUNCTION_RET_TRACER have been added. Each arch that support ftrace return
  should enable it.
- ftrace_return_stub becomes ftrace_stub.
- CONFIG_FUNCTION_RET_TRACER depends now on CONFIG_FUNCTION_TRACER
- Return traces printing can be used for other tracers on trace.c
- Adapt to the new tracing API (no more ctrl_update callback)
- Correct the check of "disabled" during insertion.
- Minor changes...

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent caf4b323

kernel/trace/Kconfig

+14 −0
Original line number Diff line number Diff line
@@ -9,6 +9,9 @@ config NOP_TRACER 
config HAVE_FUNCTION_TRACER

	bool



config HAVE_FUNCTION_RET_TRACER

	bool



config HAVE_FUNCTION_TRACE_MCOUNT_TEST

	bool

	help
@@ -54,6 +57,17 @@ config FUNCTION_TRACER 
	  (the bootup default), then the overhead of the instructions is very

	  small and not measurable even in micro-benchmarks.



config FUNCTION_RET_TRACER

	bool "Kernel Function return Tracer"

	depends on !DYNAMIC_FTRACE

	depends on HAVE_FUNCTION_RET_TRACER

	depends on FUNCTION_TRACER

	help

	  Enable the kernel to trace a function at its return.

	  It's first purpose is to trace the duration of functions.

	  This is done by setting the current return address on the thread

	  info structure of the current task.



config IRQSOFF_TRACER

	bool "Interrupts-off Latency Tracer"

	default n

kernel/trace/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -24,5 +24,6 @@ obj-$(CONFIG_NOP_TRACER) += trace_nop.o 
obj-$(CONFIG_STACK_TRACER) += trace_stack.o

obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o

obj-$(CONFIG_BOOT_TRACER) += trace_boot.o

obj-$(CONFIG_FUNCTION_RET_TRACER) += trace_functions_return.o



libftrace-y := ftrace.o

kernel/trace/ftrace.c

+16 −0
Original line number Diff line number Diff line
@@ -1484,3 +1484,19 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, 
	return ret;

}



#ifdef CONFIG_FUNCTION_RET_TRACER

trace_function_return_t ftrace_function_return =

			(trace_function_return_t)ftrace_stub;

void register_ftrace_return(trace_function_return_t func)

{

	ftrace_function_return = func;

}



void unregister_ftrace_return(void)

{

	ftrace_function_return = (trace_function_return_t)ftrace_stub;

}

#endif

kernel/trace/trace.c

+57 −8
Original line number Diff line number Diff line
@@ -244,13 +244,6 @@ unsigned long nsecs_to_usecs(unsigned long nsecs) 
	return nsecs / 1000;

}



/*

 * TRACE_ITER_SYM_MASK masks the options in trace_flags that

 * control the output of kernel symbols.

 */

#define TRACE_ITER_SYM_MASK \

	(TRACE_ITER_PRINT_PARENT|TRACE_ITER_SYM_OFFSET|TRACE_ITER_SYM_ADDR)



/* These must match the bit postions in trace_iterator_flags */

static const char *trace_options[] = {

	"print-parent",
@@ -810,6 +803,35 @@ trace_function(struct trace_array *tr, struct trace_array_cpu *data, 
	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);

}



#ifdef CONFIG_FUNCTION_RET_TRACER

static void __trace_function_return(struct trace_array *tr,

				struct trace_array_cpu *data,

				struct ftrace_retfunc *trace,

				unsigned long flags,

				int pc)

{

	struct ring_buffer_event *event;

	struct ftrace_ret_entry *entry;

	unsigned long irq_flags;



	if (unlikely(local_read(&__get_cpu_var(ftrace_cpu_disabled))))

		return;



	event = ring_buffer_lock_reserve(global_trace.buffer, sizeof(*entry),

					 &irq_flags);

	if (!event)

		return;

	entry	= ring_buffer_event_data(event);

	tracing_generic_entry_update(&entry->ent, flags, pc);

	entry->ent.type			= TRACE_FN_RET;

	entry->ip			= trace->func;

	entry->parent_ip	= trace->ret;

	entry->rettime		= trace->rettime;

	entry->calltime		= trace->calltime;

	ring_buffer_unlock_commit(global_trace.buffer, event, irq_flags);

}

#endif



void

ftrace(struct trace_array *tr, struct trace_array_cpu *data,

       unsigned long ip, unsigned long parent_ip, unsigned long flags,
@@ -1038,6 +1060,29 @@ function_trace_call(unsigned long ip, unsigned long parent_ip) 
	raw_local_irq_restore(flags);

}



#ifdef CONFIG_FUNCTION_RET_TRACER

void trace_function_return(struct ftrace_retfunc *trace)

{

	struct trace_array *tr = &global_trace;

	struct trace_array_cpu *data;

	unsigned long flags;

	long disabled;

	int cpu;

	int pc;



	raw_local_irq_save(flags);

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];

	disabled = atomic_inc_return(&data->disabled);

	if (likely(disabled == 1)) {

		pc = preempt_count();

		__trace_function_return(tr, data, trace, flags, pc);

	}

	atomic_dec(&data->disabled);

	raw_local_irq_restore(flags);

}

#endif /* CONFIG_FUNCTION_RET_TRACER */



static struct ftrace_ops trace_ops __read_mostly =

{

	.func = function_trace_call,
@@ -1285,7 +1330,7 @@ seq_print_sym_offset(struct trace_seq *s, const char *fmt, 
# define IP_FMT "%016lx"

#endif



static int

int

seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)

{

	int ret;
@@ -1738,6 +1783,10 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter) 
			trace_seq_print_cont(s, iter);

		break;

	}

	case TRACE_FN_RET: {

		return print_return_function(iter);

		break;

	}

	}

	return TRACE_TYPE_HANDLED;

}

kernel/trace/trace.h

+35 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ enum trace_type { 
	TRACE_MMIO_RW,

	TRACE_MMIO_MAP,

	TRACE_BOOT,

	TRACE_FN_RET,



	__TRACE_LAST_TYPE

};
@@ -48,6 +49,15 @@ struct ftrace_entry { 
	unsigned long		ip;

	unsigned long		parent_ip;

};



/* Function return entry */

struct ftrace_ret_entry {

	struct trace_entry	ent;

	unsigned long		ip;

	unsigned long		parent_ip;

	unsigned long long	calltime;

	unsigned long long	rettime;

};

extern struct tracer boot_tracer;



/*
@@ -218,6 +228,7 @@ extern void __ftrace_bad_type(void); 
		IF_ASSIGN(var, ent, struct trace_mmiotrace_map,		\

			  TRACE_MMIO_MAP);				\

		IF_ASSIGN(var, ent, struct trace_boot, TRACE_BOOT);	\

		IF_ASSIGN(var, ent, struct ftrace_ret_entry, TRACE_FN_RET); \

		__ftrace_bad_type();					\

	} while (0)
@@ -321,6 +332,8 @@ void trace_function(struct trace_array *tr, 
		    unsigned long ip,

		    unsigned long parent_ip,

		    unsigned long flags, int pc);

void

trace_function_return(struct ftrace_retfunc *trace);



void tracing_start_cmdline_record(void);

void tracing_stop_cmdline_record(void);
@@ -393,6 +406,10 @@ extern void *head_page(struct trace_array_cpu *data); 
extern int trace_seq_printf(struct trace_seq *s, const char *fmt, ...);

extern void trace_seq_print_cont(struct trace_seq *s,

				 struct trace_iterator *iter);



extern int

seq_print_ip_sym(struct trace_seq *s, unsigned long ip,

		unsigned long sym_flags);

extern ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf,

				 size_t cnt);

extern long ns2usecs(cycle_t nsec);
@@ -400,6 +417,17 @@ extern int trace_vprintk(unsigned long ip, const char *fmt, va_list args); 


extern unsigned long trace_flags;



/* Standard output formatting function used for function return traces */

#ifdef CONFIG_FUNCTION_RET_TRACER

extern enum print_line_t print_return_function(struct trace_iterator *iter);

#else

static inline enum print_line_t

print_return_function(struct trace_iterator *iter)

{

	return TRACE_TYPE_UNHANDLED;

}

#endif



/*

 * trace_iterator_flags is an enumeration that defines bit

 * positions into trace_flags that controls the output.
@@ -422,6 +450,13 @@ enum trace_iterator_flags { 
	TRACE_ITER_PREEMPTONLY		= 0x800,

};



/*

 * TRACE_ITER_SYM_MASK masks the options in trace_flags that

 * control the output of kernel symbols.

 */

#define TRACE_ITER_SYM_MASK \

	(TRACE_ITER_PRINT_PARENT|TRACE_ITER_SYM_OFFSET|TRACE_ITER_SYM_ADDR)



extern struct tracer nop_trace;



/**

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