path: root/kernel/trace/trace_events.c
diff options
authorSteven Rostedt <srostedt@redhat.com>2010-04-22 10:35:55 -0400
committerSteven Rostedt <rostedt@goodmis.org>2010-05-14 14:20:23 -0400
commit2e33af029556cb8bd22bf4f86f42d540249177ea (patch)
tree8a479d21300c7692d61093846054f626e3e71ed5 /kernel/trace/trace_events.c
parent2239291aeb0379fe47980b0e560e0eb9fd7e82ec (diff)
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>
Diffstat (limited to 'kernel/trace/trace_events.c')
1 files changed, 36 insertions, 12 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 19d1eb0a7188..acc0f55742c3 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -29,11 +29,23 @@ DEFINE_MUTEX(event_mutex);
+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 @@ int trace_define_field(struct ftrace_event_call *call, const char *type,
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 @@ static int trace_define_common_fields(struct ftrace_event_call *call)
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) {
@@ -111,7 +126,6 @@ int trace_event_raw_init(struct ftrace_event_call *call)
if (!id)
return -ENODEV;
call->id = id;
- INIT_LIST_HEAD(&call->fields);
return 0;
@@ -537,6 +551,7 @@ event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
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 @@ event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
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 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
const struct file_operations *filter,
const struct file_operations *format)
+ struct list_head *head;
int ret;
@@ -957,14 +974,21 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
- 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,

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