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Commit 5d4a9dba authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

tracing: only show tracing_max_latency when latency tracer configured 



The tracing_max_latency file should only be present when one of the
latency tracers ({preempt|irqs}off, wakeup*) are enabled.

This patch also removes tracing_thresh when latency tracers are not
enabled, as well as compiles out code that is only used for latency
tracers.

Reported-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent c0729be9

kernel/trace/trace.c

+50 −42
Original line number Diff line number Diff line
@@ -43,9 +43,6 @@ 


#define TRACE_BUFFER_FLAGS	(RB_FL_OVERWRITE)



unsigned long __read_mostly	tracing_max_latency;

unsigned long __read_mostly	tracing_thresh;



/*

 * On boot up, the ring buffer is set to the minimum size, so that

 * we do not waste memory on systems that are not using tracing.
@@ -338,45 +335,6 @@ static struct { 


int trace_clock_id;



/*

 * ftrace_max_lock is used to protect the swapping of buffers

 * when taking a max snapshot. The buffers themselves are

 * protected by per_cpu spinlocks. But the action of the swap

 * needs its own lock.

 *

 * This is defined as a raw_spinlock_t in order to help

 * with performance when lockdep debugging is enabled.

 */

static raw_spinlock_t ftrace_max_lock =

	(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;



/*

 * Copy the new maximum trace into the separate maximum-trace

 * structure. (this way the maximum trace is permanently saved,

 * for later retrieval via /sys/kernel/debug/tracing/latency_trace)

 */

static void

__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)

{

	struct trace_array_cpu *data = tr->data[cpu];



	max_tr.cpu = cpu;

	max_tr.time_start = data->preempt_timestamp;



	data = max_tr.data[cpu];

	data->saved_latency = tracing_max_latency;



	memcpy(data->comm, tsk->comm, TASK_COMM_LEN);

	data->pid = tsk->pid;

	data->uid = task_uid(tsk);

	data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;

	data->policy = tsk->policy;

	data->rt_priority = tsk->rt_priority;



	/* record this tasks comm */

	tracing_record_cmdline(tsk);

}



ssize_t trace_seq_to_user(struct trace_seq *s, char __user *ubuf, size_t cnt)

{

	int len;
@@ -420,6 +378,53 @@ static ssize_t trace_seq_to_buffer(struct trace_seq *s, void *buf, size_t cnt) 
	return cnt;

}



/*

 * ftrace_max_lock is used to protect the swapping of buffers

 * when taking a max snapshot. The buffers themselves are

 * protected by per_cpu spinlocks. But the action of the swap

 * needs its own lock.

 *

 * This is defined as a raw_spinlock_t in order to help

 * with performance when lockdep debugging is enabled.

 *

 * It is also used in other places outside the update_max_tr

 * so it needs to be defined outside of the

 * CONFIG_TRACER_MAX_TRACE.

 */

static raw_spinlock_t ftrace_max_lock =

	(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;



#ifdef CONFIG_TRACER_MAX_TRACE

unsigned long __read_mostly	tracing_max_latency;

unsigned long __read_mostly	tracing_thresh;



/*

 * Copy the new maximum trace into the separate maximum-trace

 * structure. (this way the maximum trace is permanently saved,

 * for later retrieval via /sys/kernel/debug/tracing/latency_trace)

 */

static void

__update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)

{

	struct trace_array_cpu *data = tr->data[cpu];



	max_tr.cpu = cpu;

	max_tr.time_start = data->preempt_timestamp;



	data = max_tr.data[cpu];

	data->saved_latency = tracing_max_latency;



	memcpy(data->comm, tsk->comm, TASK_COMM_LEN);

	data->pid = tsk->pid;

	data->uid = task_uid(tsk);

	data->nice = tsk->static_prio - 20 - MAX_RT_PRIO;

	data->policy = tsk->policy;

	data->rt_priority = tsk->rt_priority;



	/* record this tasks comm */

	tracing_record_cmdline(tsk);

}



/**

 * update_max_tr - snapshot all trace buffers from global_trace to max_tr

 * @tr: tracer
@@ -476,6 +481,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu) 
	__update_max_tr(tr, tsk, cpu);

	__raw_spin_unlock(&ftrace_max_lock);

}

#endif /* CONFIG_TRACER_MAX_TRACE */



/**

 * register_tracer - register a tracer with the ftrace system.
@@ -3952,11 +3958,13 @@ static __init int tracer_init_debugfs(void) 
	trace_create_file("current_tracer", 0644, d_tracer,

			&global_trace, &set_tracer_fops);



#ifdef CONFIG_TRACER_MAX_TRACE

	trace_create_file("tracing_max_latency", 0644, d_tracer,

			&tracing_max_latency, &tracing_max_lat_fops);



	trace_create_file("tracing_thresh", 0644, d_tracer,

			&tracing_thresh, &tracing_max_lat_fops);

#endif



	trace_create_file("README", 0444, d_tracer,

			NULL, &tracing_readme_fops);

kernel/trace/trace.h

+2 −0
Original line number Diff line number Diff line
@@ -473,12 +473,14 @@ void unregister_tracer(struct tracer *type); 


extern unsigned long nsecs_to_usecs(unsigned long nsecs);



#ifdef CONFIG_TRACER_MAX_TRACE

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);

#endif /* CONFIG_TRACER_MAX_TRACE */



#ifdef CONFIG_STACKTRACE

void ftrace_trace_stack(struct trace_array *tr, unsigned long flags,