tracing/filters: Defer pred allocation

init_preds() allocates about 5392 bytes of memory (on x86_32) for
a TRACE_EVENT. With my config, at system boot total memory occupied
is:

	5392 * (642 + 15) == 3459KB

642 == cat available_events | wc -l
15 == number of dirs in events/ftrace

That's quite a lot, so we'd better defer memory allocation util
it's needed, that's when filter is used.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <4A9B8EA5.6020700@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 41 insertions, 10 deletions

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 9f03082c81d8..c6b2edfb7fe9 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -309,7 +309,7 @@ void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s)
         struct event_filter *filter = call->filter;
 
         mutex_lock(&event_mutex);
-        if (filter->filter_string)
+        if (filter && filter->filter_string)
                 trace_seq_printf(s, "%s\n", filter->filter_string);
         else
                 trace_seq_printf(s, "none\n");
@@ -322,7 +322,7 @@ void print_subsystem_event_filter(struct event_subsystem *system,
         struct event_filter *filter = system->filter;
 
         mutex_lock(&event_mutex);
-        if (filter->filter_string)
+        if (filter && filter->filter_string)
                 trace_seq_printf(s, "%s\n", filter->filter_string);
         else
                 trace_seq_printf(s, "none\n");
@@ -390,6 +390,9 @@ void destroy_preds(struct ftrace_event_call *call)
         struct event_filter *filter = call->filter;
         int i;
 
+        if (!filter)
+                return;
+
         for (i = 0; i < MAX_FILTER_PRED; i++) {
                 if (filter->preds[i])
                         filter_free_pred(filter->preds[i]);
@@ -400,7 +403,7 @@ void destroy_preds(struct ftrace_event_call *call)
         call->filter = NULL;
 }
 
-int init_preds(struct ftrace_event_call *call)
+static int init_preds(struct ftrace_event_call *call)
 {
         struct event_filter *filter;
         struct filter_pred *pred;
@@ -410,7 +413,6 @@ int init_preds(struct ftrace_event_call *call)
         if (!call->filter)
                 return -ENOMEM;
 
-        call->filter_active = 0;
         filter->n_preds = 0;
 
         filter->preds = kzalloc(MAX_FILTER_PRED * sizeof(pred), GFP_KERNEL);
@@ -432,7 +434,28 @@ oom:
 
         return -ENOMEM;
 }
-EXPORT_SYMBOL_GPL(init_preds);
+
+static int init_subsystem_preds(struct event_subsystem *system)
+{
+        struct ftrace_event_call *call;
+        int err;
+
+        list_for_each_entry(call, &ftrace_events, list) {
+                if (!call->define_fields)
+                        continue;
+
+                if (strcmp(call->system, system->name) != 0)
+                        continue;
+
+                if (!call->filter) {
+                        err = init_preds(call);
+                        if (err)
+                                return err;
+                }
+        }
+
+        return 0;
+}
 
 enum {
         FILTER_DISABLE_ALL,
@@ -449,6 +472,9 @@ static void filter_free_subsystem_preds(struct event_subsystem *system,
                 if (!call->define_fields)
                         continue;
 
+                if (strcmp(call->system, system->name) != 0)
+                        continue;
+
                 if (flag == FILTER_INIT_NO_RESET) {
                         call->filter->no_reset = false;
                         continue;
@@ -457,10 +483,8 @@ static void filter_free_subsystem_preds(struct event_subsystem *system,
                 if (flag == FILTER_SKIP_NO_RESET && call->filter->no_reset)
                         continue;
 
-                if (!strcmp(call->system, system->name)) {
-                        filter_disable_preds(call);
-                        remove_filter_string(call->filter);
-                }
+                filter_disable_preds(call);
+                remove_filter_string(call->filter);
         }
 }
 
@@ -1094,6 +1118,10 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
 
         mutex_lock(&event_mutex);
 
+        err = init_preds(call);
+        if (err)
+                goto out_unlock;
+
         if (!strcmp(strstrip(filter_string), "0")) {
                 filter_disable_preds(call);
                 remove_filter_string(call->filter);
@@ -1139,6 +1167,10 @@ int apply_subsystem_event_filter(struct event_subsystem *system,
 
         mutex_lock(&event_mutex);
 
+        err = init_subsystem_preds(system);
+        if (err)
+                goto out_unlock;
+
         if (!strcmp(strstrip(filter_string), "0")) {
                 filter_free_subsystem_preds(system, FILTER_DISABLE_ALL);
                 remove_filter_string(system->filter);
diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
index 029a91f42287..df1bf6e48bb9 100644
--- a/kernel/trace/trace_export.c
+++ b/kernel/trace/trace_export.c
@@ -135,7 +135,6 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
 static int ftrace_raw_init_event_##call(void)                           \
 {                                                                       \
         INIT_LIST_HEAD(&event_##call.fields);                           \
-        init_preds(&event_##call);                                      \
         return 0;                                                       \
 }                                                                       \