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Commit cdd31cd2 authored by Ingo Molnar's avatar Ingo Molnar Committed by Thomas Gleixner
Browse files

ftrace: remove-idx-sync 



remove idx syncing - it's expensive on SMP.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 53c37c17

kernel/trace/trace.c

+5 −35
Original line number Diff line number Diff line
@@ -99,7 +99,6 @@ notrace cycle_t ftrace_now(int cpu) 
	return time;

}



static atomic_t			tracer_counter;

static struct trace_array	global_trace;



static DEFINE_PER_CPU(struct trace_array_cpu, global_trace_cpu);
@@ -661,7 +660,6 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags) 


	pc = preempt_count();



	entry->idx		= atomic_inc_return(&tracer_counter);

	entry->preempt_count	= pc & 0xff;

	entry->pid		= tsk->pid;

	entry->t		= ftrace_now(raw_smp_processor_id());
@@ -757,8 +755,10 @@ find_next_entry(struct trace_iterator *iter, int *ent_cpu) 
		if (!head_page(tr->data[cpu]))

			continue;

		ent = trace_entry_idx(tr, tr->data[cpu], iter, cpu);

		if (ent &&

		    (!next || (long)(next->idx - ent->idx) > 0)) {

		/*

		 * Pick the entry with the smallest timestamp:

		 */

		if (ent && (!next || ent->t < next->t)) {

			next = ent;

			next_cpu = cpu;

		}
@@ -800,8 +800,6 @@ trace_consume(struct trace_iterator *iter) 
	if (data->trace_head == data->trace_tail &&

	    data->trace_head_idx == data->trace_tail_idx)

		data->trace_idx = 0;



	trace_iterator_increment(iter);

}



static notrace void *
@@ -1160,33 +1158,6 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu) 
	}

}



static notrace void sync_time_offset(struct trace_iterator *iter)

{

	struct trace_array_cpu *prev_array, *array;

	struct trace_entry *prev_entry, *entry;

	cycle_t prev_t, t;



	entry = iter->ent;

	prev_entry = iter->prev_ent;

	if (!prev_entry)

		return;



	prev_array = iter->tr->data[iter->prev_cpu];

	array = iter->tr->data[iter->cpu];



	prev_t = prev_entry->t + prev_array->time_offset;

	t = entry->t + array->time_offset;



	/*

	 * If time goes backwards we increase the offset of

	 * the current array, to not have observable time warps.

	 * This will quickly synchronize the time offsets of

	 * multiple CPUs:

	 */

	if (t < prev_t)

		array->time_offset += prev_t - t;

}



static notrace int

print_trace_fmt(struct trace_iterator *iter)

{
@@ -1200,12 +1171,11 @@ print_trace_fmt(struct trace_iterator *iter) 
	int S;

	int ret;



	sync_time_offset(iter);

	entry = iter->ent;



	comm = trace_find_cmdline(iter->ent->pid);



	t = ns2usecs(entry->t + iter->tr->data[iter->cpu]->time_offset);

	t = ns2usecs(entry->t);

	usec_rem = do_div(t, 1000000ULL);

	secs = (unsigned long)t;

kernel/trace/trace.h

+0 −2
Original line number Diff line number Diff line
@@ -38,7 +38,6 @@ struct trace_entry { 
	char			preempt_count;

	int			pid;

	cycle_t			t;

	unsigned long		idx;

	union {

		struct ftrace_entry		fn;

		struct ctx_switch_entry		ctx;
@@ -57,7 +56,6 @@ struct trace_array_cpu { 
	atomic_t		disabled;

	spinlock_t		lock;

	struct lock_class_key	lock_key;

	cycle_t			time_offset;



	/* these fields get copied into max-trace: */

	unsigned		trace_head_idx;