linux-kernel - Re: [PATCH v9 14/22] tracing: Add hist trigger 'hex' modifier for displaying numeric fields

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Message-ID: <20150719132233.GD25163@danjae.kornet>
Date:	Sun, 19 Jul 2015 22:22:33 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc:	rostedt@...dmis.org, daniel.wagner@...-carit.de,
	masami.hiramatsu.pt@...achi.com, josh@...htriplett.org,
	andi@...stfloor.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 14/22] tracing: Add hist trigger 'hex' modifier for
 displaying numeric fields

Hi Tom,

On Thu, Jul 16, 2015 at 12:22:47PM -0500, Tom Zanussi wrote:
> Allow users to have numeric fields displayed as hex values in the
> output by appending '.hex' to field names:
> 
>    # echo hist:keys=aaa,bbb.hex:vals=ccc.hex ... \
>               [ if filter] > event/trigger
> 
> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> ---
>  kernel/trace/trace.c             |  5 +++-
>  kernel/trace/trace_events_hist.c | 49 +++++++++++++++++++++++++++++++++++++---
>  2 files changed, 50 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 27daa28..14f9472 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3810,7 +3810,10 @@ static const char readme_msg[] =
>  	"\t    entry is a simple list of the keys and values comprising the\n"
>  	"\t    entry; keys are printed first and are delineated by curly\n"
>  	"\t    braces, and are followed by the set of value fields for the\n"
> -	"\t    entry.  Numeric fields are displayed as base-10 integers.\n"
> +	"\t    entry.  By default, numeric fields are displayed as base-10\n"
> +	"\t    integers.  This can be modified by appending any of the\n"
> +	"\t    following modifiers to the field name:\n\n"
> +	"\t            .hex        display a number as a hex value\n\n"
>  	"\t    By default, the size of the hash table is 2048 entries.  The\n"
>  	"\t    'size' param can be used to specify more or fewer than that.\n"
>  	"\t    The units are in terms of hashtable entries - if a run uses\n"
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index d8259fe..9cc38ee 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -72,6 +72,7 @@ enum hist_field_flags {
>  	HIST_FIELD_HITCOUNT	= 1,
>  	HIST_FIELD_KEY		= 2,
>  	HIST_FIELD_STRING	= 4,
> +	HIST_FIELD_HEX		= 8,
>  };
>  
>  struct hist_trigger_attrs {
> @@ -284,9 +285,20 @@ static int create_val_field(struct hist_trigger_data *hist_data,
>  {
>  	struct ftrace_event_field *field = NULL;
>  	unsigned long flags = 0;
> +	char *field_name;
>  	int ret = 0;
>  
> -	field = trace_find_event_field(file->event_call, field_str);
> +	field_name = strsep(&field_str, ".");
> +	if (field_str) {
> +		if (!strcmp(field_str, "hex"))
> +			flags |= HIST_FIELD_HEX;
> +		else {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +	}
> +
> +	field = trace_find_event_field(file->event_call, field_name);
>  	if (!field) {
>  		ret = -EINVAL;
>  		goto out;
> @@ -349,11 +361,22 @@ static int create_key_field(struct hist_trigger_data *hist_data,
>  	struct ftrace_event_field *field = NULL;
>  	unsigned long flags = 0;
>  	unsigned int key_size;
> +	char *field_name;
>  	int ret = 0;
>  
>  	flags |= HIST_FIELD_KEY;
>  
> -	field = trace_find_event_field(file->event_call, field_str);
> +	field_name = strsep(&field_str, ".");
> +	if (field_str) {
> +		if (!strcmp(field_str, "hex"))
> +			flags |= HIST_FIELD_HEX;
> +		else {
> +			ret = -EINVAL;
> +			goto out;
> +		}
> +	}
> +
> +	field = trace_find_event_field(file->event_call, field_name);
>  	if (!field) {
>  		ret = -EINVAL;
>  		goto out;
> @@ -688,7 +711,11 @@ hist_trigger_entry_print(struct seq_file *m,
>  		if (i > hist_data->n_vals)
>  			seq_puts(m, ", ");
>  
> -		if (key_field->flags & HIST_FIELD_STRING) {
> +		if (key_field->flags & HIST_FIELD_HEX) {
> +			uval = *(u64 *)(key + key_field->offset);
> +			seq_printf(m, "%s: %llx",
> +				   key_field->field->name, uval);
> +		} else if (key_field->flags & HIST_FIELD_STRING) {
>  			seq_printf(m, "%s: %-35s", key_field->field->name,
>  				   (char *)(key + key_field->offset));
>  		} else {

It seems the '.hex' modifier only affects key fields' output..

Thanks,
Namhyung


> @@ -791,9 +818,25 @@ const struct file_operations event_hist_fops = {
>  	.release = single_release,
>  };
>  
> +static const char *get_hist_field_flags(struct hist_field *hist_field)
> +{
> +	const char *flags_str = NULL;
> +
> +	if (hist_field->flags & HIST_FIELD_HEX)
> +		flags_str = "hex";
> +
> +	return flags_str;
> +}
> +
>  static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
>  {
>  	seq_printf(m, "%s", hist_field->field->name);
> +	if (hist_field->flags) {
> +		const char *flags_str = get_hist_field_flags(hist_field);
> +
> +		if (flags_str)
> +			seq_printf(m, ".%s", flags_str);
> +	}
>  }
>  
>  static int event_hist_trigger_print(struct seq_file *m,
> -- 
> 1.9.3
> 
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