linux-kernel - Re: [PATCH 2/6] tracing: event_id_read() uses simple buffer instead of trace

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Message-ID: <20100120180428.GC5017@nowhere>
Date:	Wed, 20 Jan 2010 19:04:29 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/6] tracing: event_id_read() uses simple buffer
	instead of trace_seq

On Tue, Jan 19, 2010 at 03:34:01PM +0800, Lai Jiangshan wrote:
> 
> It seems that struct trace_seq is too heavy for event_id_read().
> we use simple buffer instead of struct trace_seq.
> 
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>


Acked-by: Frederic Weisbecker <fweisbec@...il.com>



> ---
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 04d3f90..835b370 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -604,23 +604,16 @@ static ssize_t
>  event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
>  {
>  	struct ftrace_event_call *call = filp->private_data;
> -	struct trace_seq *s;
> -	int r;
> +	char buf[20];
> +	int len;
>  
>  	if (*ppos)
>  		return 0;
>  
> -	s = kmalloc(sizeof(*s), GFP_KERNEL);
> -	if (!s)
> -		return -ENOMEM;
> +	len = snprintf(buf, sizeof(buf), "%d\n", call->id);
> +	len = simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
>  
> -	trace_seq_init(s);
> -	trace_seq_printf(s, "%d\n", call->id);
> -
> -	r = simple_read_from_buffer(ubuf, cnt, ppos,
> -				    s->buffer, s->len);
> -	kfree(s);
> -	return r;
> +	return len;
>  }
>  
>  static ssize_t
> 
> 

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