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| author | Tom Zanussi <tom.zanussi@linux.intel.com> | 2018-01-15 20:51:40 -0600 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2018-03-10 16:05:50 -0500 |
| commit | dc4e2801d400b0346fb281ce9cf010d611e2243c (patch) | |
| tree | c02ee22ac10758d4cf4d23fd9ed85934cdf0c80f /include/linux | |
| parent | 00b4145298aeb05a2d110117ed18148cb21ebd14 (diff) | |
| download | lwn-dc4e2801d400b0346fb281ce9cf010d611e2243c.tar.gz lwn-dc4e2801d400b0346fb281ce9cf010d611e2243c.zip | |
ring-buffer: Redefine the unimplemented RINGBUF_TYPE_TIME_STAMP
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.
Link: http://lkml.kernel.org/r/477b362dba1ce7fab9889a1a8e885a62c472f041.1516069914.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/ring_buffer.h | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h index 025159e17e1b..7cb84774c20d 100644 --- a/include/linux/ring_buffer.h +++ b/include/linux/ring_buffer.h @@ -34,10 +34,12 @@ struct ring_buffer_event { * array[0] = time delta (28 .. 59) * size = 8 bytes * - * @RINGBUF_TYPE_TIME_STAMP: Sync time stamp with external clock - * array[0] = tv_nsec - * array[1..2] = tv_sec - * size = 16 bytes + * @RINGBUF_TYPE_TIME_STAMP: Absolute timestamp + * Same format as TIME_EXTEND except that the + * value is an absolute timestamp, not a delta + * event.time_delta contains bottom 27 bits + * array[0] = top (28 .. 59) bits + * size = 8 bytes * * <= @RINGBUF_TYPE_DATA_TYPE_LEN_MAX: * Data record @@ -54,12 +56,12 @@ enum ring_buffer_type { RINGBUF_TYPE_DATA_TYPE_LEN_MAX = 28, RINGBUF_TYPE_PADDING, RINGBUF_TYPE_TIME_EXTEND, - /* FIXME: RINGBUF_TYPE_TIME_STAMP not implemented */ RINGBUF_TYPE_TIME_STAMP, }; 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); /* * ring_buffer_discard_commit will remove an event that has not |