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tracing: Define new ftrace event "func_repeats"

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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

Link: https://lkml.kernel.org/r/20210415181854.147448-3-y.karadz@gmail.com

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Yordan Karadzhov (VMware) 2021-04-15 21:18:50 +03:00 committed by Steven Rostedt (VMware)
parent eaa7a89720
commit f689e4f280
3 changed files with 73 additions and 0 deletions
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3
kernel/trace/trace.h
View File

@ -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)

22
kernel/trace/trace_entries.h
View File

@ -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) \
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: -%llu)",
(void *)__entry->ip,
(void *)__entry->parent_ip,
__entry->count,
FUNC_REPEATS_GET_DELTA_TS(__entry))
);

48
kernel/trace/trace_output.c
View File

@ -1381,6 +1381,53 @@ 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, last_ts:", field->count);
trace_print_time(s, iter,
iter->ts - FUNC_REPEATS_GET_DELTA_TS(field));
trace_seq_puts(s, ")\n");
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,
@ -1393,6 +1440,7 @@ static struct trace_event *events[] __initdata = {
&trace_print_event,
&trace_hwlat_event,
&trace_raw_data_event,
&trace_func_repeats_event,
NULL
};