tracing: Don't allocate common fields for every trace events

Every event has the same common fields, so it's a big waste of
memory to have a copy of those fields for every event.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BFA3759.30105@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 81 insertions, 52 deletions

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 01ce088c1cdf..cc90ccdad469 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -698,6 +698,8 @@ struct filter_pred {
         int                     pop_n;
 };
 
+extern struct list_head ftrace_common_fields;
+
 extern enum regex_type
 filter_parse_regex(char *buff, int len, char **search, int *not);
 extern void print_event_filter(struct ftrace_event_call *call,
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index a594f9a7ee3d..d3b4bdf00b39 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -28,6 +28,7 @@
 DEFINE_MUTEX(event_mutex);
 
 LIST_HEAD(ftrace_events);
+LIST_HEAD(ftrace_common_fields);
 
 struct list_head *
 trace_get_fields(struct ftrace_event_call *event_call)
@@ -37,15 +38,11 @@ trace_get_fields(struct ftrace_event_call *event_call)
         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)
+static int __trace_define_field(struct list_head *head, 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)
@@ -68,7 +65,6 @@ int trace_define_field(struct ftrace_event_call *call, const char *type,
         field->size = size;
         field->is_signed = is_signed;
 
-        head = trace_get_fields(call);
         list_add(&field->link, head);
 
         return 0;
@@ -80,17 +76,32 @@ err:
 
         return -ENOMEM;
 }
+
+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 list_head *head;
+
+        if (WARN_ON(!call->class))
+                return 0;
+
+        head = trace_get_fields(call);
+        return __trace_define_field(head, type, name, offset, size,
+                                    is_signed, filter_type);
+}
 EXPORT_SYMBOL_GPL(trace_define_field);
 
 #define __common_field(type, item)                                      \
-        ret = trace_define_field(call, #type, "common_" #item,          \
-                                 offsetof(typeof(ent), item),           \
-                                 sizeof(ent.item),                      \
-                                 is_signed_type(type), FILTER_OTHER);   \
+        ret = __trace_define_field(&ftrace_common_fields, #type,        \
+                                   "common_" #item,                     \
+                                   offsetof(typeof(ent), item),         \
+                                   sizeof(ent.item),                    \
+                                   is_signed_type(type), FILTER_OTHER); \
         if (ret)                                                        \
                 return ret;
 
-static int trace_define_common_fields(struct ftrace_event_call *call)
+static int trace_define_common_fields(void)
 {
         int ret;
         struct trace_entry ent;
@@ -544,32 +555,10 @@ out:
         return ret;
 }
 
-static ssize_t
-event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
-                  loff_t *ppos)
+static void print_event_fields(struct trace_seq *s, struct list_head *head)
 {
-        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;
-        int r = 0;
-
-        if (*ppos)
-                return 0;
-
-        s = kmalloc(sizeof(*s), GFP_KERNEL);
-        if (!s)
-                return -ENOMEM;
-
-        trace_seq_init(s);
 
-        trace_seq_printf(s, "name: %s\n", call->name);
-        trace_seq_printf(s, "ID: %d\n", call->event.type);
-        trace_seq_printf(s, "format:\n");
-
-        head = trace_get_fields(call);
         list_for_each_entry_reverse(field, head, link) {
                 /*
                  * Smartly shows the array type(except dynamic array).
@@ -584,29 +573,54 @@ event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
                         array_descriptor = NULL;
 
                 if (!array_descriptor) {
-                        r = trace_seq_printf(s, "\tfield:%s %s;\toffset:%u;"
+                        trace_seq_printf(s, "\tfield:%s %s;\toffset:%u;"
                                         "\tsize:%u;\tsigned:%d;\n",
                                         field->type, field->name, field->offset,
                                         field->size, !!field->is_signed);
                 } else {
-                        r = trace_seq_printf(s, "\tfield:%.*s %s%s;\toffset:%u;"
+                        trace_seq_printf(s, "\tfield:%.*s %s%s;\toffset:%u;"
                                         "\tsize:%u;\tsigned:%d;\n",
                                         (int)(array_descriptor - field->type),
                                         field->type, field->name,
                                         array_descriptor, field->offset,
                                         field->size, !!field->is_signed);
                 }
+        }
+}
 
-                if (--common_field_count == 0)
-                        r = trace_seq_printf(s, "\n");
+static ssize_t
+event_format_read(struct file *filp, char __user *ubuf, size_t cnt,
+                  loff_t *ppos)
+{
+        struct ftrace_event_call *call = filp->private_data;
+        struct list_head *head;
+        struct trace_seq *s;
+        char *buf;
+        int r;
 
-                if (!r)
-                        break;
-        }
+        if (*ppos)
+                return 0;
 
-        if (r)
-                r = trace_seq_printf(s, "\nprint fmt: %s\n",
-                                call->print_fmt);
+        s = kmalloc(sizeof(*s), GFP_KERNEL);
+        if (!s)
+                return -ENOMEM;
+
+        trace_seq_init(s);
+
+        trace_seq_printf(s, "name: %s\n", call->name);
+        trace_seq_printf(s, "ID: %d\n", call->event.type);
+        trace_seq_printf(s, "format:\n");
+
+        /* print common fields */
+        print_event_fields(s, &ftrace_common_fields);
+
+        trace_seq_putc(s, '\n');
+
+        /* print event specific fields */
+        head = trace_get_fields(call);
+        print_event_fields(s, head);
+
+        r = trace_seq_printf(s, "\nprint fmt: %s\n", call->print_fmt);
 
         if (!r) {
                 /*
@@ -980,9 +994,7 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
                  */
                 head = trace_get_fields(call);
                 if (list_empty(head)) {
-                        ret = trace_define_common_fields(call);
-                        if (!ret)
-                                ret = call->class->define_fields(call);
+                        ret = call->class->define_fields(call);
                         if (ret < 0) {
                                 pr_warning("Could not initialize trace point"
                                            " events/%s\n", call->name);
@@ -1319,6 +1331,9 @@ static __init int event_trace_init(void)
         trace_create_file("enable", 0644, d_events,
                           NULL, &ftrace_system_enable_fops);
 
+        if (trace_define_common_fields())
+                pr_warning("tracing: Failed to allocate common fields");
+
         for_each_event(call, __start_ftrace_events, __stop_ftrace_events) {
                 /* The linker may leave blanks */
                 if (!call->name)
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 57bb1bb32999..330fefd1de1c 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -497,12 +497,10 @@ void print_subsystem_event_filter(struct event_subsystem *system,
 }
 
 static struct ftrace_event_field *
-find_event_field(struct ftrace_event_call *call, char *name)
+__find_event_field(struct list_head *head, char *name)
 {
         struct ftrace_event_field *field;
-        struct list_head *head;
 
-        head = trace_get_fields(call);
         list_for_each_entry(field, head, link) {
                 if (!strcmp(field->name, name))
                         return field;
@@ -511,6 +509,20 @@ find_event_field(struct ftrace_event_call *call, char *name)
         return NULL;
 }
 
+static struct ftrace_event_field *
+find_event_field(struct ftrace_event_call *call, char *name)
+{
+        struct ftrace_event_field *field;
+        struct list_head *head;
+
+        field = __find_event_field(&ftrace_common_fields, name);
+        if (field)
+                return field;
+
+        head = trace_get_fields(call);
+        return __find_event_field(head, name);
+}
+
 static void filter_free_pred(struct filter_pred *pred)
 {
         if (!pred)