On Fri, 9 Apr 2021 21:10:27 +0300 "Yordan Karadzhov (VMware)" <[email protected]> wrote:
> The event aims to consolidate the function tracing record in the cases > when a single function is called number of times consecutively. > > while (cond) > do_func(); > > This may happen in various scenarios (busy waiting for example). > The new ftrace event can be used to show repeated function events with > a single event and save space on the ring buffer > > Signed-off-by: Yordan Karadzhov (VMware) <[email protected]> > --- > kernel/trace/trace.h | 3 +++ > kernel/trace/trace_entries.h | 22 +++++++++++++++++ > kernel/trace/trace_output.c | 47 ++++++++++++++++++++++++++++++++++++ > 3 files changed, 72 insertions(+) > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > index 5506424eae2a..6a5b4c2a0fa7 100644 > --- a/kernel/trace/trace.h > +++ b/kernel/trace/trace.h > @@ -45,6 +45,7 @@ enum trace_type { > TRACE_BPUTS, > TRACE_HWLAT, > TRACE_RAW_DATA, > + TRACE_FUNC_REPEATS, > > __TRACE_LAST_TYPE, > }; > @@ -442,6 +443,8 @@ extern void __ftrace_bad_type(void); > TRACE_GRAPH_ENT); \ > IF_ASSIGN(var, ent, struct ftrace_graph_ret_entry, \ > TRACE_GRAPH_RET); \ > + IF_ASSIGN(var, ent, struct func_repeats_entry, \ > + TRACE_FUNC_REPEATS); \ > __ftrace_bad_type(); \ > } while (0) > > diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h > index 4547ac59da61..fdd022a7aecf 100644 > --- a/kernel/trace/trace_entries.h > +++ b/kernel/trace/trace_entries.h > @@ -338,3 +338,25 @@ FTRACE_ENTRY(hwlat, hwlat_entry, > __entry->nmi_total_ts, > __entry->nmi_count) > ); > + > +#define FUNC_REPEATS_GET_DELTA_TS(entry) \ > +(((u64)entry->top_delta_ts << 32) | entry->bottom_delta_ts) \ Have macros have side effects by their parameters, it is always recommended to wrap them around parenthesis: #define FUNC_REPEATS_GET_DELTA_TS(entry) \ (((u64)(entry)->top_delta_ts << 32) | (entry)->bottom_delta_ts) \ And have the next line start with at tab after the #define. I would normally ignore this issue if it was just used in this header file, because tracing macros are "special", but it's used in actual code as well. -- Steve > + > +FTRACE_ENTRY(func_repeats, func_repeats_entry, > + > + TRACE_FUNC_REPEATS, > + > + F_STRUCT( > + __field( unsigned long, ip ) > + __field( unsigned long, parent_ip ) > + __field( u16 , count ) > + __field( u16 , top_delta_ts ) > + __field( u32 , bottom_delta_ts ) > + ), > + > + F_printk(" %ps <-%ps\t(repeats:%u delta_ts: -%llu)", > + (void *)__entry->ip, > + (void *)__entry->parent_ip, > + __entry->count, > + FUNC_REPEATS_GET_DELTA_TS(__entry)) > +); > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c > index a0146e1fffdf..55b08e146afc 100644 > --- a/kernel/trace/trace_output.c > +++ b/kernel/trace/trace_output.c > @@ -1373,6 +1373,52 @@ static struct trace_event trace_raw_data_event = { > .funcs = &trace_raw_data_funcs, > }; > > +static enum print_line_t > +trace_func_repeats_raw(struct trace_iterator *iter, int flags, > + struct trace_event *event) > +{ > + struct func_repeats_entry *field; > + struct trace_seq *s = &iter->seq; > + > + trace_assign_type(field, iter->ent); > + > + trace_seq_printf(s, "%lu %lu %u %llu\n", > + field->ip, > + field->parent_ip, > + field->count, > + FUNC_REPEATS_GET_DELTA_TS(field)); > + > + return trace_handle_return(s); > +} > + > +static enum print_line_t > +trace_func_repeats_print(struct trace_iterator *iter, int flags, > + struct trace_event *event) > +{ > + struct func_repeats_entry *field; > + struct trace_seq *s = &iter->seq; > + > + trace_assign_type(field, iter->ent); > + > + seq_print_ip_sym(s, field->ip, flags); > + trace_seq_puts(s, " <-"); > + seq_print_ip_sym(s, field->parent_ip, flags); > + trace_seq_printf(s, " (repeats: %u, delta_ts: -%llu)\n", > + field->count, > + FUNC_REPEATS_GET_DELTA_TS(field)); > + > + return trace_handle_return(s); > +} > + > +static struct trace_event_functions trace_func_repeats_funcs = { > + .trace = trace_func_repeats_print, > + .raw = trace_func_repeats_raw, > +}; > + > +static struct trace_event trace_func_repeats_event = { > + .type = TRACE_FUNC_REPEATS, > + .funcs = &trace_func_repeats_funcs, > +}; > > static struct trace_event *events[] __initdata = { > &trace_fn_event, > @@ -1385,6 +1431,7 @@ static struct trace_event *events[] __initdata = { > &trace_print_event, > &trace_hwlat_event, > &trace_raw_data_event, > + &trace_func_repeats_event, > NULL > }; >
