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. v4 changes: * "[PATCH 1/5] Define static void trace_print_time()" is added to the patch-set. This patch simply applies the modification suggested by Steven Rostedt in his review of v3. My contribution to the code of this patch is really negligible. * FUNC_REPEATS_GET_DELTA_TS macro is improved. * The way we print the time of the last function repeat is improved. * "tracer_alloc_func_repeats(struct trace_array *tr)" is removed from trace.h. * FUNC_REPEATS_GET_DELTA_TS macro is replased by a static inline function 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) (6): tracing: Define static void trace_print_time() 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 | 35 ++++++ kernel/trace/trace.h | 19 +++ kernel/trace/trace_entries.h | 22 ++++ kernel/trace/trace_functions.c | 223 ++++++++++++++++++++++++++++----- kernel/trace/trace_output.c | 74 +++++++++-- 5 files changed, 336 insertions(+), 37 deletions(-) -- 2.25.1