Commit bc0c38d1 authored by Steven Rostedt's avatar Steven Rostedt Committed by Thomas Gleixner
Browse files

ftrace: latency tracer infrastructure

This patch adds the latency tracer infrastructure. This patch
does not add anything that will select and turn it on, but will
be used by later patches.

If it were to be compiled, it would add the following files
to the debugfs:

 The root tracing directory:


This patch also adds the following files:

     list of available tracers. Currently no tracers are
     available. Looking into this file only shows
     "none" which is used to unregister all tracers.

     The trace that is currently active. Empty on start up.
     To switch to a tracer simply echo one of the tracers that
     are listed in available_tracers:

   example: (used with later patches)

      echo function > /debugfs/tracing/current_tracer

     To disable the tracer:

       echo disable > /debugfs/tracing/current_tracer

     echoing "1" into this file starts the ftrace function tracing
      (if sysctl kernel.ftrace_enabled=1)
     echoing "0" turns it off.

      This file is readonly and holds the result of the trace.

      This file outputs a easier to read version of the trace.

      Controls the way the output of traces look.
      So far there's two controls:
        echoing in "symonly" will only show the kallsyms variables
            without the addresses (if kallsyms was configured)
        echoing in "verbose" will change the output to show
            a lot more data, but not very easy to understand by
        echoing in "nosymonly" turns off symonly.
        echoing in "noverbose" turns off verbose.
Signed-off-by: default avatarSteven Rostedt <>
Signed-off-by: default avatarArnaldo Carvalho de Melo <>
Signed-off-by: default avatarIngo Molnar <>
Signed-off-by: default avatarThomas Gleixner <>
parent 16444a8a
......@@ -70,6 +70,7 @@ obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
obj-$(CONFIG_MARKERS) += marker.o
obj-$(CONFIG_LATENCYTOP) += latencytop.o
obj-$(CONFIG_FTRACE) += trace/
obj-$(CONFIG_TRACING) += trace/
# According to Alan Modra <>, the -fno-omit-frame-pointer is
......@@ -3,3 +3,8 @@
config TRACING
select DEBUG_FS
obj-$(CONFIG_FTRACE) += libftrace.o
obj-$(CONFIG_TRACING) += trace.o
libftrace-y := ftrace.o
This diff is collapsed.
#include <linux/fs.h>
#include <asm/atomic.h>
#include <linux/sched.h>
#include <linux/clocksource.h>
* Function trace entry - function address and parent function addres:
struct ftrace_entry {
unsigned long ip;
unsigned long parent_ip;
* Context switch trace entry - which task (and prio) we switched from/to:
struct ctx_switch_entry {
unsigned int prev_pid;
unsigned char prev_prio;
unsigned char prev_state;
unsigned int next_pid;
unsigned char next_prio;
* The trace entry - the most basic unit of tracing. This is what
* is printed in the end as a single line in the trace output, such as:
* bash-15816 [01] 235.197585: idle_cpu <- irq_enter
struct trace_entry {
char type;
char cpu;
char flags;
char preempt_count;
int pid;
cycle_t t;
unsigned long idx;
union {
struct ftrace_entry fn;
struct ctx_switch_entry ctx;
#define TRACE_ENTRY_SIZE sizeof(struct trace_entry)
* The CPU trace array - it consists of thousands of trace entries
* plus some other descriptor data: (for example which task started
* the trace, etc.)
struct trace_array_cpu {
void *trace;
unsigned long trace_idx;
atomic_t disabled;
atomic_t underrun;
unsigned long saved_latency;
unsigned long critical_start;
unsigned long critical_end;
unsigned long critical_sequence;
unsigned long nice;
unsigned long policy;
unsigned long rt_priority;
cycle_t preempt_timestamp;
pid_t pid;
uid_t uid;
char comm[TASK_COMM_LEN];
struct trace_iterator;
* The trace array - an array of per-CPU trace arrays. This is the
* highest level data structure that individual tracers deal with.
* They have on/off state as well:
struct trace_array {
unsigned long entries;
long ctrl;
int cpu;
cycle_t time_start;
struct trace_array_cpu *data[NR_CPUS];
* A specific tracer, represented by methods that operate on a trace array:
struct tracer {
const char *name;
void (*init)(struct trace_array *tr);
void (*reset)(struct trace_array *tr);
void (*open)(struct trace_iterator *iter);
void (*close)(struct trace_iterator *iter);
void (*start)(struct trace_iterator *iter);
void (*stop)(struct trace_iterator *iter);
void (*ctrl_update)(struct trace_array *tr);
struct tracer *next;
int print_max;
* Trace iterator - used by printout routines who present trace
* results to users and which routines might sleep, etc:
struct trace_iterator {
struct trace_array *tr;
struct tracer *trace;
struct trace_entry *ent;
unsigned long iter_flags;
loff_t pos;
unsigned long next_idx[NR_CPUS];
int cpu;
int idx;
void notrace tracing_reset(struct trace_array_cpu *data);
int tracing_open_generic(struct inode *inode, struct file *filp);
struct dentry *tracing_init_dentry(void);
void ftrace(struct trace_array *tr,
struct trace_array_cpu *data,
unsigned long ip,
unsigned long parent_ip,
unsigned long flags);
void tracing_sched_switch_trace(struct trace_array *tr,
struct trace_array_cpu *data,
struct task_struct *prev,
struct task_struct *next,
unsigned long flags);
void tracing_record_cmdline(struct task_struct *tsk);
void tracing_start_function_trace(void);
void tracing_stop_function_trace(void);
int register_tracer(struct tracer *type);
void unregister_tracer(struct tracer *type);
extern unsigned long nsecs_to_usecs(unsigned long nsecs);
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,
struct task_struct *tsk, int cpu);
static inline notrace cycle_t now(int cpu)
return cpu_clock(cpu);
extern void notrace
wakeup_sched_switch(struct task_struct *prev, struct task_struct *next);
static inline void
wakeup_sched_switch(struct task_struct *prev, struct task_struct *next)
typedef void
(*tracer_switch_func_t)(void *private,
struct task_struct *prev,
struct task_struct *next);
struct tracer_switch_ops {
tracer_switch_func_t func;
void *private;
struct tracer_switch_ops *next;
extern int register_tracer_switch(struct tracer_switch_ops *ops);
extern int unregister_tracer_switch(struct tracer_switch_ops *ops);
extern unsigned long ftrace_update_tot_cnt;
#endif /* _LINUX_KERNEL_TRACE_H */
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