Commit efe6196a authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

ring-buffer: Allow ring_buffer_event_time_stamp() to return time stamp of all events 

Currently, ring_buffer_event_time_stamp() only returns an accurate time
stamp of the event if it has an absolute extended time stamp attached to
it. To make it more robust, use the event_stamp() in case the event does
not have an absolute value attached to it.

This will allow ring_buffer_event_time_stamp() to be used in more cases
than just histograms, and it will also allow histograms to not require
including absolute values all the time.

Link: https://lkml.kernel.org/r/20210316164113.704830885@goodmis.org



Reviewed-by: default avatarTom Zanussi <zanussi@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent b47e3302

include/linux/ring_buffer.h

+2 −1
Original line number Diff line number Diff line
@@ -61,7 +61,8 @@ enum ring_buffer_type { 


unsigned ring_buffer_event_length(struct ring_buffer_event *event);

void *ring_buffer_event_data(struct ring_buffer_event *event);

u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event);

u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,

				 struct ring_buffer_event *event);



/*

 * ring_buffer_discard_commit will remove an event that has not

kernel/trace/ring_buffer.c

+45 −15
Original line number Diff line number Diff line
@@ -298,21 +298,6 @@ static u64 rb_event_time_stamp(struct ring_buffer_event *event) 
	return ts;

}



/**

 * ring_buffer_event_time_stamp - return the event's extended timestamp

 * @event: the event to get the timestamp of

 *

 * Returns the extended timestamp associated with a data event.

 * An extended time_stamp is a 64-bit timestamp represented

 * internally in a special way that makes the best use of space

 * contained within a ring buffer event.  This function decodes

 * it and maps it to a straight u64 value.

 */

u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event)

{

	return rb_event_time_stamp(event);

}



/* Flag when events were overwritten */

#define RB_MISSED_EVENTS	(1 << 31)

/* Missed count stored at end */
@@ -757,6 +742,51 @@ static bool rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set) 
}

#endif



static inline u64 rb_time_stamp(struct trace_buffer *buffer);



/**

 * ring_buffer_event_time_stamp - return the event's current time stamp

 * @buffer: The buffer that the event is on

 * @event: the event to get the time stamp of

 *

 * Note, this must be called after @event is reserved, and before it is

 * committed to the ring buffer. And must be called from the same

 * context where the event was reserved (normal, softirq, irq, etc).

 *

 * Returns the time stamp associated with the current event.

 * If the event has an extended time stamp, then that is used as

 * the time stamp to return.

 * In the highly unlikely case that the event was nested more than

 * the max nesting, then the write_stamp of the buffer is returned,

 * otherwise  current time is returned, but that really neither of

 * the last two cases should ever happen.

 */

u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,

				 struct ring_buffer_event *event)

{

	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];

	unsigned int nest;

	u64 ts;



	/* If the event includes an absolute time, then just use that */

	if (event->type_len == RINGBUF_TYPE_TIME_STAMP)

		return rb_event_time_stamp(event);



	/* Read the current saved nesting level time stamp */

	nest = local_read(&cpu_buffer->committing) - 1;

	if (likely(nest < MAX_NEST))

		return cpu_buffer->event_stamp[nest];



	WARN_ON_ONCE(1);



	/* Can only fail on 32 bit */

	if (!rb_time_read(&cpu_buffer->write_stamp, &ts))

		/* Screw it, just read the current time */

		ts = rb_time_stamp(cpu_buffer->buffer);



	return ts;

}



/**

 * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer

 * @buffer: The ring_buffer to get the number of pages from

kernel/trace/trace_events_hist.c

+1 −1
Original line number Diff line number Diff line
@@ -644,7 +644,7 @@ static u64 hist_field_timestamp(struct hist_field *hist_field, 
	struct hist_trigger_data *hist_data = hist_field->hist_data;

	struct trace_array *tr = hist_data->event_file->tr;



	u64 ts = ring_buffer_event_time_stamp(rbe);

	u64 ts = ring_buffer_event_time_stamp(buffer, rbe);



	if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr))

		ts = ns2usecs(ts);