tracing: Move fields from event to class structure
Move the defined fields from the event to the class structure.
Since the fields of the event are defined by the class they belong
to, it makes sense to have the class hold the information instead
of the individual events. The events of the same class would just
hold duplicate information.
After this change the size of the kernel dropped another 3K:
text data bss dec hex filename
4913961 1088356 861512 6863829 68bbd5 vmlinux.orig
4900252 1057412 861512 6819176 680d68 vmlinux.regs
4900375 1053380 861512 6815267 67fe23 vmlinux.fields
Although the text increased, this was mainly due to the C files
having to adapt to the change. This is a constant increase, where
new tracepoints will not increase the Text. But the big drop is
in the data size (as well as needed allocations to hold the fields).
This will give even more savings as more tracepoints are created.
Note, if just TRACE_EVENT()s are used and not DECLARE_EVENT_CLASS()
with several DEFINE_EVENT()s, then the savings will be lost. But
we are pushing developers to consolidate events with DEFINE_EVENT()
so this should not be an issue.
The kprobes define a unique class to every new event, but are dynamic
so it should not be a issue.
The syscalls however have a single class but the fields for the individual
events are different. The syscalls use a metadata to define the
fields. I moved the fields list from the event to the metadata and
added a "get_fields()" function to the class. This function is used
to find the fields. For normal events and kprobes, get_fields() just
returns a pointer to the fields list_head in the class. For syscall
events, it returns the fields list_head in the metadata for the event.
v2: Fixed the syscall fields. The syscall metadata needs a list
of fields for both enter and exit.
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 19d1eb0..acc0f55 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -29,11 +29,23 @@
LIST_HEAD(ftrace_events);
+struct list_head *
+trace_get_fields(struct ftrace_event_call *event_call)
+{
+ if (!event_call->class->get_fields)
+ return &event_call->class->fields;
+ return event_call->class->get_fields(event_call);
+}
+
int trace_define_field(struct ftrace_event_call *call, const char *type,
const char *name, int offset, int size, int is_signed,
int filter_type)
{
struct ftrace_event_field *field;
+ struct list_head *head;
+
+ if (WARN_ON(!call->class))
+ return 0;
field = kzalloc(sizeof(*field), GFP_KERNEL);
if (!field)
@@ -56,7 +68,8 @@
field->size = size;
field->is_signed = is_signed;
- list_add(&field->link, &call->fields);
+ head = trace_get_fields(call);
+ list_add(&field->link, head);
return 0;
@@ -94,8 +107,10 @@
void trace_destroy_fields(struct ftrace_event_call *call)
{
struct ftrace_event_field *field, *next;
+ struct list_head *head;
- list_for_each_entry_safe(field, next, &call->fields, link) {
+ head = trace_get_fields(call);
+ list_for_each_entry_safe(field, next, head, link) {
list_del(&field->link);
kfree(field->type);
kfree(field->name);
@@ -111,7 +126,6 @@
if (!id)
return -ENODEV;
call->id = id;
- INIT_LIST_HEAD(&call->fields);
return 0;
}
@@ -537,6 +551,7 @@
{
struct ftrace_event_call *call = filp->private_data;
struct ftrace_event_field *field;
+ struct list_head *head;
struct trace_seq *s;
int common_field_count = 5;
char *buf;
@@ -555,7 +570,8 @@
trace_seq_printf(s, "ID: %d\n", call->id);
trace_seq_printf(s, "format:\n");
- list_for_each_entry_reverse(field, &call->fields, link) {
+ head = trace_get_fields(call);
+ list_for_each_entry_reverse(field, head, link) {
/*
* Smartly shows the array type(except dynamic array).
* Normal:
@@ -931,6 +947,7 @@
const struct file_operations *filter,
const struct file_operations *format)
{
+ struct list_head *head;
int ret;
/*
@@ -957,14 +974,21 @@
id);
#endif
- if (call->define_fields) {
- ret = trace_define_common_fields(call);
- if (!ret)
- ret = call->define_fields(call);
- if (ret < 0) {
- pr_warning("Could not initialize trace point"
- " events/%s\n", call->name);
- return ret;
+ if (call->class->define_fields) {
+ /*
+ * Other events may have the same class. Only update
+ * the fields if they are not already defined.
+ */
+ head = trace_get_fields(call);
+ if (list_empty(head)) {
+ ret = trace_define_common_fields(call);
+ if (!ret)
+ ret = call->class->define_fields(call);
+ if (ret < 0) {
+ pr_warning("Could not initialize trace point"
+ " events/%s\n", call->name);
+ return ret;
+ }
}
trace_create_file("filter", 0644, call->dir, call,
filter);