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Commit 37886f6a authored by Steven Rostedt's avatar Steven Rostedt
Browse files

ring-buffer: add api to allow a tracer to change clock source 



This patch adds a new function called ring_buffer_set_clock that
allows a tracer to assign its own clock source to the buffer.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent 6adaad14

include/linux/ring_buffer.h

+5 −2
Original line number Diff line number Diff line
@@ -118,8 +118,11 @@ unsigned long ring_buffer_overruns(struct ring_buffer *buffer); 
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu);

unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu);



u64 ring_buffer_time_stamp(int cpu);

void ring_buffer_normalize_time_stamp(int cpu, u64 *ts);

u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu);

void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,

				      int cpu, u64 *ts);

void ring_buffer_set_clock(struct ring_buffer *buffer,

			   u64 (*clock)(void));



size_t ring_buffer_page_len(void *page);

kernel/trace/ring_buffer.c

+38 −27
Original line number Diff line number Diff line
@@ -180,29 +180,6 @@ EXPORT_SYMBOL_GPL(tracing_is_on); 


#include "trace.h"



/* Up this if you want to test the TIME_EXTENTS and normalization */

#define DEBUG_SHIFT 0



u64 ring_buffer_time_stamp(int cpu)

{

	u64 time;



	preempt_disable_notrace();

	/* shift to debug/test normalization and TIME_EXTENTS */

	time = trace_clock_local() << DEBUG_SHIFT;

	preempt_enable_no_resched_notrace();



	return time;

}

EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);



void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)

{

	/* Just stupid testing the normalize function and deltas */

	*ts >>= DEBUG_SHIFT;

}

EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);



#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))

#define RB_ALIGNMENT		4U

#define RB_MAX_SMALL_DATA	28
@@ -374,6 +351,7 @@ struct ring_buffer { 
#ifdef CONFIG_HOTPLUG_CPU

	struct notifier_block		cpu_notify;

#endif

	u64				(*clock)(void);

};



struct ring_buffer_iter {
@@ -394,6 +372,30 @@ struct ring_buffer_iter { 
		_____ret;					\

	})



/* Up this if you want to test the TIME_EXTENTS and normalization */

#define DEBUG_SHIFT 0



u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)

{

	u64 time;



	preempt_disable_notrace();

	/* shift to debug/test normalization and TIME_EXTENTS */

	time = buffer->clock() << DEBUG_SHIFT;

	preempt_enable_no_resched_notrace();



	return time;

}

EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);



void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,

				      int cpu, u64 *ts)

{

	/* Just stupid testing the normalize function and deltas */

	*ts >>= DEBUG_SHIFT;

}

EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);



/**

 * check_pages - integrity check of buffer pages

 * @cpu_buffer: CPU buffer with pages to test
@@ -569,6 +571,7 @@ struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags) 


	buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);

	buffer->flags = flags;

	buffer->clock = trace_clock_local;



	/* need at least two pages */

	if (buffer->pages == 1)
@@ -645,6 +648,12 @@ ring_buffer_free(struct ring_buffer *buffer) 
}

EXPORT_SYMBOL_GPL(ring_buffer_free);



void ring_buffer_set_clock(struct ring_buffer *buffer,

			   u64 (*clock)(void))

{

	buffer->clock = clock;

}



static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);



static void
@@ -1191,7 +1200,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, 
			cpu_buffer->tail_page = next_page;



			/* reread the time stamp */

			*ts = ring_buffer_time_stamp(cpu_buffer->cpu);

			*ts = ring_buffer_time_stamp(buffer, cpu_buffer->cpu);

			cpu_buffer->tail_page->page->time_stamp = *ts;

		}
@@ -1334,7 +1343,7 @@ rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer, 
	if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))

		return NULL;



	ts = ring_buffer_time_stamp(cpu_buffer->cpu);

	ts = ring_buffer_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);



	/*

	 * Only the first commit can update the timestamp.
@@ -2051,7 +2060,8 @@ rb_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts) 
	case RINGBUF_TYPE_DATA:

		if (ts) {

			*ts = cpu_buffer->read_stamp + event->time_delta;

			ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);

			ring_buffer_normalize_time_stamp(buffer,

							 cpu_buffer->cpu, ts);

		}

		return event;
@@ -2112,7 +2122,8 @@ rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts) 
	case RINGBUF_TYPE_DATA:

		if (ts) {

			*ts = iter->read_stamp + event->time_delta;

			ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);

			ring_buffer_normalize_time_stamp(buffer,

							 cpu_buffer->cpu, ts);

		}

		return event;

kernel/trace/trace.c

+14 −7
Original line number Diff line number Diff line
@@ -155,13 +155,6 @@ ns2usecs(cycle_t nsec) 
	return nsec;

}



cycle_t ftrace_now(int cpu)

{

	u64 ts = ring_buffer_time_stamp(cpu);

	ring_buffer_normalize_time_stamp(cpu, &ts);

	return ts;

}



/*

 * The global_trace is the descriptor that holds the tracing

 * buffers for the live tracing. For each CPU, it contains
@@ -178,6 +171,20 @@ static struct trace_array global_trace; 


static DEFINE_PER_CPU(struct trace_array_cpu, global_trace_cpu);



cycle_t ftrace_now(int cpu)

{

	u64 ts;



	/* Early boot up does not have a buffer yet */

	if (!global_trace.buffer)

		return trace_clock_local();



	ts = ring_buffer_time_stamp(global_trace.buffer, cpu);

	ring_buffer_normalize_time_stamp(global_trace.buffer, cpu, &ts);



	return ts;

}



/*

 * The max_tr is used to snapshot the global_trace when a maximum

 * latency is reached. Some tracers will use this to store a maximum