linux-kernel - Re: [PATCH v2] tracing: Add verbose gfp

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Date:   Thu, 11 Jul 2019 10:42:33 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     Zhengjun Xing <zhengjun.xing@...ux.intel.com>, rostedt@...dmis.org,
        mingo@...hat.com, tom.zanussi@...ux.intel.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tracing: Add verbose gfp_flag printing to synthetic
 events

Hi Zhengjun,

The patch itself looks fine to me, but could you please create a v3
with a couple changes to the commit message?  I noticed you dropped
your original commit message - please add it back and combine with part
of mine, as below.  Also, please keep your original Subject line
('[PATCH] trace:add "gfp_t" support in synthetic_events') (but the
first word after trace:, 'add', should be capitalized.) 

On Thu, 2019-07-11 at 16:46 +0800, Zhengjun Xing wrote:
> Add on top of 'trace:add "gfp_t" support in synthetic_events'.

Please remove this part but keep the part below.

> 
> Prints the gfp flags as hex in addition to the human-readable flag
> string.  Example output:
> 
>   whoopsie-630 [000] ...1 78.969452: testevent: bar=b20
> (GFP_ATOMIC|__GFP_ZERO)
>     rcuc/0-11  [000] ...1 81.097555: testevent: bar=a20 (GFP_ATOMIC)
>     rcuc/0-11  [000] ...1 81.583123: testevent: bar=a20 (GFP_ATOMIC)
> 

So basically, something like this:

[PATCH] trace: Add "gfp_t" support in synthetic_events

Add "gfp_t" support in synthetic_events, then the "gfp_t" type
parameter in some functions can be traced.

Print the gfp flags as hex in addition to the human-readable flag
string.  Example output:

  whoopsie-630 [000] ...1 78.969452: testevent: bar=b20 (GFP_ATOMIC|__GFP_ZERO)
    rcuc/0-11  [000] ...1 81.097555: testevent: bar=a20 (GFP_ATOMIC)
    rcuc/0-11  [000] ...1 81.583123: testevent: bar=a20 (GFP_ATOMIC)

> Signed-off-by: Tom Zanussi <zanussi@...nel.org>
> Signed-off-by: Zhengjun Xing <zhengjun.xing@...ux.intel.com>


Thanks,

Tom

> ---
>  kernel/trace/trace_events_hist.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/kernel/trace/trace_events_hist.c
> b/kernel/trace/trace_events_hist.c
> index ca6b0dff60c5..938ef3f54c5c 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -13,6 +13,10 @@
>  #include <linux/rculist.h>
>  #include <linux/tracefs.h>
>  
> +/* for gfp flag names */
> +#include <linux/trace_events.h>
> +#include <trace/events/mmflags.h>
> +
>  #include "tracing_map.h"
>  #include "trace.h"
>  #include "trace_dynevent.h"
> @@ -752,6 +756,8 @@ static int synth_field_size(char *type)
>  		size = sizeof(unsigned long);
>  	else if (strcmp(type, "pid_t") == 0)
>  		size = sizeof(pid_t);
> +	else if (strcmp(type, "gfp_t") == 0)
> +		size = sizeof(gfp_t);
>  	else if (synth_field_is_string(type))
>  		size = synth_field_string_size(type);
>  
> @@ -792,6 +798,8 @@ static const char *synth_field_fmt(char *type)
>  		fmt = "%lu";
>  	else if (strcmp(type, "pid_t") == 0)
>  		fmt = "%d";
> +	else if (strcmp(type, "gfp_t") == 0)
> +		fmt = "%x";
>  	else if (synth_field_is_string(type))
>  		fmt = "%s";
>  
> @@ -834,9 +838,20 @@ static enum print_line_t
> print_synth_event(struct trace_iterator *iter,
>  					 i == se->n_fields - 1 ? ""
> : " ");
>  			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
>  		} else {
> +			struct trace_print_flags __flags[] = {
> +			    __def_gfpflag_names, {-1, NULL} };
> +
>  			trace_seq_printf(s, print_fmt, se-
> >fields[i]->name,
>  					 entry->fields[n_u64],
>  					 i == se->n_fields - 1 ? ""
> : " ");
> +
> +			if (strcmp(se->fields[i]->type, "gfp_t") ==
> 0) {
> +				trace_seq_puts(s, " (");
> +				trace_print_flags_seq(s, "|",
> +						      entry-
> >fields[n_u64],
> +						      __flags);
> +				trace_seq_putc(s, ')');
> +			}
>  			n_u64++;
>  		}
>  	}