From: "Yordan Karadzhov (VMware)" <y.kar...@gmail.com>
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.kar...@gmail.com
Signed-off-by: Yordan Karadzhov (VMware) <y.kar...@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org>
---
kernel/trace/trace.h | 3 +++
kernel/trace/trace_entries.h | 22 +++++++++++++++++
kernel/trace/trace_output.c | 48 ++++++++++++++++++++++++++++++++++++
3 files changed, 73 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..251c819cf0c5 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) \
+
+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))
+);
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 333233d45596..3037f0c88f90 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -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
};
--
2.30.1
