Re: tracer_init_tracefs really slow

[Steven Rostedt]

On Mon, 07 Dec 2020 17:24:58 +0100
Lucas Stach <l.st...@pengutronix.de> wrote:

> I would be happy to test a patch on our whimpy machines, though. :)

Let me know if this helps:

-- Steve

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 06134189e9a7..48aa5b6a7d15 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9062,7 +9062,10 @@ int tracing_init_dentry(void)
 extern struct trace_eval_map *__start_ftrace_eval_maps[];
 extern struct trace_eval_map *__stop_ftrace_eval_maps[];
 
-static void __init trace_eval_init(void)
+static struct workqueue_struct *eval_map_wq __initdata;
+struct work_struct eval_map_work __initdata;
+
+static void __init eval_map_work_func(struct work_struct *work)
 {
        int len;
 
@@ -9070,6 +9073,34 @@ static void __init trace_eval_init(void)
        trace_insert_eval_map(NULL, __start_ftrace_eval_maps, len);
 }
 
+static int __init trace_eval_init(void)
+{
+       INIT_WORK(&eval_map_work, eval_map_work_func);
+
+       eval_map_wq = alloc_workqueue("eval_map_wq", WQ_UNBOUND, 0);
+       if (!eval_map_wq) {
+               pr_err("Unable to allocate eval_map_wq\n");
+               /* Do work here */
+               eval_map_work_func(&eval_map_work);
+               return -ENOMEM;
+       }
+
+       queue_work(eval_map_wq, &eval_map_work);
+       return 0;
+}
+
+static int __init trace_eval_sync(void)
+{
+       /* Make sure the eval map updates are finished */
+       if (eval_map_wq)
+               destroy_workqueue(eval_map_wq);
+       return 0;
+}
+
+subsys_initcall(trace_eval_init);
+late_initcall_sync(trace_eval_sync);
+
+
 #ifdef CONFIG_MODULES
 static void trace_module_add_evals(struct module *mod)
 {
@@ -9171,8 +9202,6 @@ static __init int tracer_init_tracefs(void)
        trace_create_file("saved_tgids", 0444, NULL,
                        NULL, &tracing_saved_tgids_fops);
 
-       trace_eval_init();
-
        trace_create_eval_file(NULL);
 
 #ifdef CONFIG_MODULES