[04/54] tracing: Reimplement log2

Commit Message

[e-mail] Aug. 29, 2018, 12:17 p.m. UTC

log2 as currently implemented applies only to u64 trace_event_field
derived fields, and assumes that anything it's applied to is a u64
field.

To prepare for synthetic fields like latencies, log2 should be
applicable to those as well, so take the opportunity now to fix the
current problems as well as expand to more general uses.

log2 should be thought of as a chaining function rather than a field
type.  To enable this as well as possible future function
implementations, add a hist_field operand array into the hist_field
definition for this purpose, and make use of it to implement the log2
'function'.

Link: http://lkml.kernel.org/r/b47[e-mail]

Signed-off-by: Tom Zanussi <[e-mail]>
Signed-off-by: Steven Rostedt (VMware) <[e-mail]>
(cherry picked from commit 5819eaddf35b24d628ddfa4fbb5f8d4026e44b96)
Signed-off-by: Hirotaka MOTAI <[e-mail]>
---
 kernel/trace/trace_events_hist.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

Patch

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 34edf5fd..1e1558c9 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -23,22 +23,26 @@ 
 
 #include "tracing_map.h"
 #include "trace.h"
 
 struct hist_field;
 
 typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event);
 
+#define HIST_FIELD_OPERANDS_MAX	2
+
 struct hist_field {
 	struct ftrace_event_field	*field;
 	unsigned long			flags;
 	hist_field_fn_t			fn;
 	unsigned int			size;
 	unsigned int			offset;
+	unsigned int                    is_signed;
+	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
 };
 
 static u64 hist_field_none(struct hist_field *field, void *event)
 {
 	return 0;
 }
 
 static u64 hist_field_counter(struct hist_field *field, void *event)
@@ -66,17 +70,19 @@  static u64 hist_field_pstring(struct hist_field *hist_field, void *event)
 {
 	char **addr = (char **)(event + hist_field->field->offset);
 
 	return (u64)(unsigned long)*addr;
 }
 
 static u64 hist_field_log2(struct hist_field *hist_field, void *event)
 {
-	u64 val = *(u64 *)(event + hist_field->field->offset);
+	struct hist_field *operand = hist_field->operands[0];
+
+	u64 val = operand->fn(operand, event);
 
 	return (u64) ilog2(roundup_pow_of_two(val));
 }
 
 #define DEFINE_HIST_FIELD_FN(type)					\
 static u64 hist_field_##type(struct hist_field *hist_field, void *event)\
 {									\
 	type *addr = (type *)(event + hist_field->field->offset);	\
@@ -151,16 +157,18 @@  static const char *hist_field_name(struct hist_field *field,
 {
 	const char *field_name = "";
 
 	if (level > 1)
 		return field_name;
 
 	if (field->field)
 		field_name = field->field->name;
+	else if (field->flags & HIST_FIELD_FL_LOG2)
+		field_name = hist_field_name(field->operands[0], ++level);
 
 	if (field_name == NULL)
 		field_name = "";
 
 	return field_name;
 }
 
 static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
@@ -352,18 +360,30 @@  static void hist_trigger_elt_comm_init(struct tracing_map_elt *elt)
 
 static const struct tracing_map_ops hist_trigger_elt_comm_ops = {
 	.elt_alloc	= hist_trigger_elt_comm_alloc,
 	.elt_copy	= hist_trigger_elt_comm_copy,
 	.elt_free	= hist_trigger_elt_comm_free,
 	.elt_init	= hist_trigger_elt_comm_init,
 };
 
-static void destroy_hist_field(struct hist_field *hist_field)
+static void destroy_hist_field(struct hist_field *hist_field,
+			       unsigned int level)
 {
+	unsigned int i;
+
+	if (level > 2)
+		return;
+
+	if (!hist_field)
+		return;
+
+	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
+		destroy_hist_field(hist_field->operands[i], level + 1);
+
 	kfree(hist_field);
 }
 
 static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 					    unsigned long flags)
 {
 	struct hist_field *hist_field;
 
@@ -380,17 +400,20 @@  static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 	}
 
 	if (flags & HIST_FIELD_FL_STACKTRACE) {
 		hist_field->fn = hist_field_none;
 		goto out;
 	}
 
 	if (flags & HIST_FIELD_FL_LOG2) {
+		unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
 		hist_field->fn = hist_field_log2;
+		hist_field->operands[0] = create_hist_field(field, fl);
+		hist_field->size = hist_field->operands[0]->size;
 		goto out;
 	}
 
 	if (WARN_ON_ONCE(!field))
 		goto out;
 
 	if (is_string_field(field)) {
 		flags |= HIST_FIELD_FL_STRING;
@@ -400,34 +423,34 @@  static struct hist_field *create_hist_field(struct ftrace_event_field *field,
 		else if (field->filter_type == FILTER_DYN_STRING)
 			hist_field->fn = hist_field_dynstring;
 		else
 			hist_field->fn = hist_field_pstring;
 	} else {
 		hist_field->fn = select_value_fn(field->size,
 						 field->is_signed);
 		if (!hist_field->fn) {
-			destroy_hist_field(hist_field);
+			destroy_hist_field(hist_field, 0);
 			return NULL;
 		}
 	}
  out:
 	hist_field->field = field;
 	hist_field->flags = flags;
 
 	return hist_field;
 }
 
 static void destroy_hist_fields(struct hist_trigger_data *hist_data)
 {
 	unsigned int i;
 
 	for (i = 0; i < TRACING_MAP_FIELDS_MAX; i++) {
 		if (hist_data->fields[i]) {
-			destroy_hist_field(hist_data->fields[i]);
+			destroy_hist_field(hist_data->fields[i], 0);
 			hist_data->fields[i] = NULL;
 		}
 	}
 }
 
 static int create_hitcount_val(struct hist_trigger_data *hist_data)
 {
 	hist_data->fields[HITCOUNT_IDX] =