linux-kernel - Re: [PATCH 1/5] trace: Add a new readonly entry to report total buffer size

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Date:	Fri, 29 Jul 2011 14:01:03 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Vaibhav Nagarnaik <vnagarnaik@...gle.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Michael Rubin <mrubin@...gle.com>,
	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] trace: Add a new readonly entry to report total
 buffer size

On Tue, 2011-07-26 at 15:59 -0700, Vaibhav Nagarnaik wrote:
> The current file "buffer_size_kb" reports the size of per-cpu buffer and
> not the overall memory allocated which could be misleading. A new file
> "buffer_total_size_kb" adds up all the enabled CPU buffer sizes and
> reports it. This is only a readonly entry.
> 
> Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@...gle.com>
> ---
>  kernel/trace/trace.c |   27 +++++++++++++++++++++++++++
>  1 files changed, 27 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index e5df02c..ce57c55 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3569,6 +3569,24 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
>  }
>  
>  static ssize_t
> +tracing_total_entries_read(struct file *filp, char __user *ubuf,
> +				size_t cnt, loff_t *ppos)
> +{
> +	struct trace_array *tr = filp->private_data;
> +	char buf[64];
> +	int r, cpu;
> +	unsigned long size = 0;
> +
> +	mutex_lock(&trace_types_lock);
> +	for_each_tracing_cpu(cpu)
> +		size += tr->entries >> 10;

Could you make this consistent with buffer_size_kb as well. That is, if
the buffer is "shrunk", could you have the expanded size printed as
well.

Thanks,

-- Steve

> +	mutex_unlock(&trace_types_lock);
> +
> +	r = sprintf(buf, "%lu\n", size);
> +	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
> +}
> +
> +static ssize_t
>  tracing_free_buffer_write(struct file *filp, const char __user *ubuf,
>  			  size_t cnt, loff_t *ppos)
>  {
> @@ -3739,6 +3757,12 @@ static const struct file_operations tracing_entries_fops = {
>  	.llseek		= generic_file_llseek,
>  };
>  
> +static const struct file_operations tracing_total_entries_fops = {
> +	.open		= tracing_open_generic,
> +	.read		= tracing_total_entries_read,
> +	.llseek		= generic_file_llseek,
> +};
> +
>  static const struct file_operations tracing_free_buffer_fops = {
>  	.write		= tracing_free_buffer_write,
>  	.release	= tracing_free_buffer_release,
> @@ -4450,6 +4474,9 @@ static __init int tracer_init_debugfs(void)
>  	trace_create_file("buffer_size_kb", 0644, d_tracer,
>  			&global_trace, &tracing_entries_fops);
>  
> +	trace_create_file("buffer_total_size_kb", 0444, d_tracer,
> +			&global_trace, &tracing_total_entries_fops);
> +
>  	trace_create_file("free_buffer", 0644, d_tracer,
>  			&global_trace, &tracing_free_buffer_fops);
>  


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