The new option for function tracing aims to save space on the ring
buffer and to make it more readable in the case when a single function
is called number of times consecutively:
while (cond)
do_func();
Instead of having an identical records for each call of the function
we will record only the first call, followed by an event showing the
number of repeats.
v3 changes:
* FUNC_REPEATS_SET_DELTA_TS macro has been optimised.
* Fixed bug in func_set_flag(): In the previous version the value
of the "new_flags" variable was not properly calculated because
I misinterpreted the meaning of the "bit" argument of the function.
This bug in v2 had no real effect, because for the moment we have
only two "function options" so the value of "new_flags" was correct,
although its way of calculating was wrong.
v2 changes:
* As suggested by Steven in his review, we now record not only the
repetition count, but also the time elapsed between the last
repetition of the function and the actual generation of the
"func_repeats" event. 16 bits are used to record the repetition
count. In the case of an overflow of the counter a second pair of
"function" and "func_repeats" events will be generated. The time
interval gets codded by using up to 48 (32 + 16) bits.
Yordan Karadzhov (VMware) (5):
tracing: Define new ftrace event "func_repeats"
tracing: Add "last_func_repeats" to struct trace_array
tracing: Add method for recording "func_repeats" events
tracing: Unify the logic for function tracing options
tracing: Add "func_no_repeats" option for function tracing
kernel/trace/trace.c | 27 ++++
kernel/trace/trace.h | 25 ++++
kernel/trace/trace_entries.h | 28 +++++
kernel/trace/trace_functions.c | 222 ++++++++++++++++++++++++++++-----
kernel/trace/trace_output.c | 47 +++++++
5 files changed, 321 insertions(+), 28 deletions(-)
--
2.25.1
