Messages in this thread Patch in this message | | | Subject | Re: tracer_init_tracefs really slow | From | Lucas Stach <> | Date | Wed, 09 Dec 2020 15:38:50 +0100 |
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Hi Steven,
Am Montag, den 07.12.2020, 14:47 -0500 schrieb Steven Rostedt: On Mon, 07 Dec 2020 17:24:58 +0100 Lucas Stach <l.stach@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);
You don't want to do this...
+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(); - ... and this. Moving the trace_eval_init into its own initcall means it gets started before tracer_init_tracefs. As it holds the trace_event_sem while updating the eval maps, event_trace_init() then blocks further initcall execution when it tries to grab this semaphore a bit down the line, killing the parallelism we are trying to unlock here.
With those 2 lines dropped, the change seems to work as intended and shaves ~830ms from the kernel boot time on this system.
Regards, Lucas
trace_create_eval_file(NULL);
#ifdef CONFIG_MODULES
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