[v2] Tracing: Accelerate Kernel Boot by Asynchronizing

[PATCH v2 1/3] tracing: Rename `eval_map_wq` and export it for asynchronous use by other modules

Posted by Yaxiong Tian 2 weeks, 1 day ago

The eval_map_work_func() function, though queued in eval_map_wq,
holds the trace_event_sem read-write lock for a long time during
kernel boot. This causes blocking issues for other functions.

Rename eval_map_wq to trace_init_wq and export it, thereby allowing
other modules to schedule work on this queue asynchronously and
avoiding blockage of the main boot thread.

Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
---
 kernel/trace/trace.c | 18 +++++++++---------
 kernel/trace/trace.h |  2 ++
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e18005807395..c61e30cb7339 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -10774,7 +10774,7 @@ int tracing_init_dentry(void)
 extern struct trace_eval_map *__start_ftrace_eval_maps[];
 extern struct trace_eval_map *__stop_ftrace_eval_maps[];
 
-static struct workqueue_struct *eval_map_wq __initdata;
+struct workqueue_struct *trace_init_wq __initdata;
 static struct work_struct eval_map_work __initdata;
 static struct work_struct tracerfs_init_work __initdata;
 
@@ -10790,15 +10790,15 @@ 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");
+	trace_init_wq = alloc_workqueue("trace_init_wq", WQ_UNBOUND, 0);
+	if (!trace_init_wq) {
+		pr_err("Unable to allocate trace_init_wq\n");
 		/* Do work here */
 		eval_map_work_func(&eval_map_work);
 		return -ENOMEM;
 	}
 
-	queue_work(eval_map_wq, &eval_map_work);
+	queue_work(trace_init_wq, &eval_map_work);
 	return 0;
 }
 
@@ -10807,8 +10807,8 @@ subsys_initcall(trace_eval_init);
 static int __init trace_eval_sync(void)
 {
 	/* Make sure the eval map updates are finished */
-	if (eval_map_wq)
-		destroy_workqueue(eval_map_wq);
+	if (trace_init_wq)
+		destroy_workqueue(trace_init_wq);
 	return 0;
 }
 
@@ -10969,9 +10969,9 @@ static __init int tracer_init_tracefs(void)
 	if (ret)
 		return 0;
 
-	if (eval_map_wq) {
+	if (trace_init_wq) {
 		INIT_WORK(&tracerfs_init_work, tracer_init_tracefs_work_func);
-		queue_work(eval_map_wq, &tracerfs_init_work);
+		queue_work(trace_init_wq, &tracerfs_init_work);
 	} else {
 		tracer_init_tracefs_work_func(NULL);
 	}
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index de4e6713b84e..e52f259f8945 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -770,6 +770,8 @@ extern unsigned long nsecs_to_usecs(unsigned long nsecs);
 
 extern unsigned long tracing_thresh;
 
+extern struct workqueue_struct *trace_init_wq __initdata;
+
 /* PID filtering */
 
 bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,
-- 
2.25.1

Re: [PATCH v2 1/3] tracing: Rename `eval_map_wq` and export it for asynchronous use by other modules

Posted by Steven Rostedt 2 weeks, 1 day ago

On Mon, 26 Jan 2026 10:43:16 +0800
Yaxiong Tian <tianyaxiong@kylinos.cn> wrote:

Hi,

Some of your terminology is a little confusing. The subject says "modules"
but no module will use it (the term module means loadable code at runtime
into the Linux kernel). A better subject would be:


  tracing: Rename `eval_map_wq` and allow other parts of tracing use it


> The eval_map_work_func() function, though queued in eval_map_wq,
> holds the trace_event_sem read-write lock for a long time during
> kernel boot. This causes blocking issues for other functions.
> 
> Rename eval_map_wq to trace_init_wq and export it, thereby allowing

Also saying "export" for a function means something like "EXPORT_SYMBOLE()"
which again deals with Linux modules. A better term is "make it global".

> other modules to schedule work on this queue asynchronously and

 .. other parts of tracing ..

> avoiding blockage of the main boot thread.
> 
> Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>

Other than that, this patch looks good.

-- Steve

> ---
>  kernel/trace/trace.c | 18 +++++++++---------
>  kernel/trace/trace.h |  2 ++
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index e18005807395..c61e30cb7339 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -10774,7 +10774,7 @@ int tracing_init_dentry(void)
>  extern struct trace_eval_map *__start_ftrace_eval_maps[];
>  extern struct trace_eval_map *__stop_ftrace_eval_maps[];
>  
> -static struct workqueue_struct *eval_map_wq __initdata;
> +struct workqueue_struct *trace_init_wq __initdata;
>  static struct work_struct eval_map_work __initdata;
>  static struct work_struct tracerfs_init_work __initdata;
>  
> @@ -10790,15 +10790,15 @@ 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");
> +	trace_init_wq = alloc_workqueue("trace_init_wq", WQ_UNBOUND, 0);
> +	if (!trace_init_wq) {
> +		pr_err("Unable to allocate trace_init_wq\n");
>  		/* Do work here */
>  		eval_map_work_func(&eval_map_work);
>  		return -ENOMEM;
>  	}
>  
> -	queue_work(eval_map_wq, &eval_map_work);
> +	queue_work(trace_init_wq, &eval_map_work);
>  	return 0;
>  }
>  
> @@ -10807,8 +10807,8 @@ subsys_initcall(trace_eval_init);
>  static int __init trace_eval_sync(void)
>  {
>  	/* Make sure the eval map updates are finished */
> -	if (eval_map_wq)
> -		destroy_workqueue(eval_map_wq);
> +	if (trace_init_wq)
> +		destroy_workqueue(trace_init_wq);
>  	return 0;
>  }
>  
> @@ -10969,9 +10969,9 @@ static __init int tracer_init_tracefs(void)
>  	if (ret)
>  		return 0;
>  
> -	if (eval_map_wq) {
> +	if (trace_init_wq) {
>  		INIT_WORK(&tracerfs_init_work, tracer_init_tracefs_work_func);
> -		queue_work(eval_map_wq, &tracerfs_init_work);
> +		queue_work(trace_init_wq, &tracerfs_init_work);
>  	} else {
>  		tracer_init_tracefs_work_func(NULL);
>  	}
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index de4e6713b84e..e52f259f8945 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -770,6 +770,8 @@ extern unsigned long nsecs_to_usecs(unsigned long nsecs);
>  
>  extern unsigned long tracing_thresh;
>  
> +extern struct workqueue_struct *trace_init_wq __initdata;
> +
>  /* PID filtering */
>  
>  bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,

Re: [PATCH v2 1/3] tracing: Rename `eval_map_wq` and export it for asynchronous use by other modules

Posted by Yaxiong Tian 2 weeks ago

在 2026/1/26 22:36, Steven Rostedt 写道:
> On Mon, 26 Jan 2026 10:43:16 +0800
> Yaxiong Tian <tianyaxiong@kylinos.cn> wrote:
>
> Hi,
>
> Some of your terminology is a little confusing. The subject says "modules"
> but no module will use it (the term module means loadable code at runtime
> into the Linux kernel). A better subject would be:
>
>
>    tracing: Rename `eval_map_wq` and allow other parts of tracing use it
>
>
>> The eval_map_work_func() function, though queued in eval_map_wq,
>> holds the trace_event_sem read-write lock for a long time during
>> kernel boot. This causes blocking issues for other functions.
>>
>> Rename eval_map_wq to trace_init_wq and export it, thereby allowing
> Also saying "export" for a function means something like "EXPORT_SYMBOLE()"
> which again deals with Linux modules. A better term is "make it global".
>
>> other modules to schedule work on this queue asynchronously and
>   .. other parts of tracing ..
>
>> avoiding blockage of the main boot thread.
>>
>> Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
> Other than that, this patch looks good.
>
> -- Steve

    Yes, those statements were not quite accurate. I have addressed them
    in Version 3.