Normally a data event includes the delta time between itself and the previous data event. But if a write interrupts another write then the event cannot check the timestamp of the previous event and so it uses a delta of 0.
Adds a new trace option: force-abs-timestamp. When this is on each event is proceeded by an absolute timestamp event. Reviewed-by: Peter Shier <[email protected]> Signed-off-by: Korben Rusek <[email protected]> --- Documentation/trace/ftrace.rst | 5 +++++ kernel/trace/trace.c | 4 ++++ kernel/trace/trace.h | 1 + 3 files changed, 10 insertions(+) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 430a16283103..704264164ffd 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -1029,6 +1029,7 @@ To see what is available, simply cat the file:: irq-info markers noevent-fork + noforce-abs-timestamp function-trace nofunction-fork nodisplay-graph @@ -1212,6 +1213,10 @@ Here are the available options: This affects PIDs listed in set_event_notrace_pid as well. + force-abs-timestamp + When set, always use absolute timestamps rather than + defaulting to deltas. + function-trace The latency tracers will enable function tracing if this option is enabled (default it is). When diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index ec44b0e2a19c..8b5c4e998895 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4852,6 +4852,12 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled) trace_printk_control(enabled); } + if (mask == TRACE_ITER_FORCE_ABS_TIMESTAMP) { + ring_buffer_set_time_stamp_abs(tr->array_buffer.buffer, enabled); +#ifdef CONFIG_TRACER_MAX_TRACE + ring_buffer_set_time_stamp_abs(tr->max_buffer.buffer, enabled); +#endif + } return 0; } diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index def769df5bf1..cb1ecc540494 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1330,6 +1330,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf, C(MARKERS, "markers"), \ C(EVENT_FORK, "event-fork"), \ C(PAUSE_ON_TRACE, "pause-on-trace"), \ + C(FORCE_ABS_TIMESTAMP, "force-abs-timestamp"), \ FUNCTION_FLAGS \ FGRAPH_FLAGS \ STACK_FLAGS \ -- 2.27.0.290.gba653c62da-goog
