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) <y.kar...@gmail.com>
---
kernel/trace/trace.h | 3 +++
kernel/trace/trace_entries.h | 39 ++++++++++++++++++++++++++++++
kernel/trace/trace_output.c | 47 ++++++++++++++++++++++++++++++++++++
3 files changed, 89 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..6f98c3b4e4fa 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -338,3 +338,42 @@ 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)
\
+
+#define FUNC_REPEATS_SET_DELTA_TS(entry, delta)
\
+ do {
\
+ if (likely(!((u64)delta >> 32))) {
\
+ entry->bottom_delta_ts = delta;
\
+ entry->top_delta_ts = 0;
\
+ } else {
\
+ if (likely(!((u64)delta >> 48))) {
\
+ entry->bottom_delta_ts = delta & U32_MAX;
\
+ entry->top_delta_ts = (delta >> 32);
\
+ } else {
\
+ /* Timestamp overflow. Set to max. */
\
+ entry->bottom_delta_ts = U32_MAX;
\
+ entry->top_delta_ts = U16_MAX;
\
+ }
\
+ }
\
+ } while (0);
\
+
+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
};
--
2.25.1
