Hi Tom,
On Mon, Oct 30, 2017 at 03:51:48PM -0500, Tom Zanussi wrote:
> RINGBUF_TYPE_TIME_STAMP is defined but not used, and from what I can
> gather was reserved for something like an absolute timestamp feature
> for the ring buffer, if not a complete replacement of the current
> time_delta scheme.
>
> This code redefines RINGBUF_TYPE_TIME_STAMP to implement absolute time
> stamps. Another way to look at it is that it essentially forces
> extended time_deltas for all events.
>
> The motivation for doing this is to enable time_deltas that aren't
> dependent on previous events in the ring buffer, making it feasible to
> use the ring_buffer_event timetamps in a more random-access way, for
> purposes other than serial event printing.
>
> To set/reset this mode, use tracing_set_timestamp_abs() from the
> previous interface patch.
>
> Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
> ---
[SNIP]
> @@ -2220,13 +2246,16 @@ static void rb_inc_iter(struct ring_buffer_iter *iter)
> }
>
> /* Slow path, do not inline */
> -static noinline struct ring_buffer_event *
> +static struct noinline ring_buffer_event *
struct noinline? Looks like a mistake..
Thanks,
Namhyung
> -rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
> +rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs)
> {
> - event->type_len = RINGBUF_TYPE_TIME_EXTEND;
> + if (abs)
> + event->type_len = RINGBUF_TYPE_TIME_STAMP;
> + else
> + event->type_len = RINGBUF_TYPE_TIME_EXTEND;
>
> - /* Not the first event on the page? */
> - if (rb_event_index(event)) {
> + /* Not the first event on the page, or not delta? */
> + if (abs || rb_event_index(event)) {
> event->time_delta = delta & TS_MASK;
> event->array[0] = delta >> TS_SHIFT;
> } else {
--
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