Re: [PATCH] trace:add "gfp_t" support in synthetic_events

[Xing Zhengjun]

Hi Tom,

On 7/11/2019 3:51 AM, Tom Zanussi wrote:
> Hi Zhengjun,
>
> On Thu, 2019-07-04 at 10:55 +0800, Zhengjun Xing wrote:
> > Add "gfp_t" support in synthetic_events, then the "gfp_t" type
> > parameter in some functions can be traced.
> >
> > Signed-off-by: Zhengjun Xing <zhengjun.xing@xxxxxxxxxxxxxxx>
> > ---
> >   kernel/trace/trace_events_hist.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/trace/trace_events_hist.c
> > b/kernel/trace/trace_events_hist.c
> > index ca6b0dff60c5..0d3ab01b7cb5 100644
> > --- a/kernel/trace/trace_events_hist.c
> > +++ b/kernel/trace/trace_events_hist.c
> > @@ -752,6 +752,8 @@ 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 +794,8 @@ 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 = "%u";
> >   	else if (synth_field_is_string(type))
> >   		fmt = "%s";
> >   
>
> This will work, but I think it would be better to display as hex, and
> also show the flags in human-readable form.
>
> How about adding something like this on top of your patch?:
Thanks, I will add it to the v2 version patch.
> [PATCH] tracing: Add verbose gfp_flag printing to synthetic events
>
> Add on top of 'trace:add "gfp_t" support in synthetic_events'.
>
> 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)
>
> Signed-off-by: Tom Zanussi <zanussi@xxxxxxxxxx>
> ---
>   kernel/trace/trace_events_hist.c | 17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 0d3ab01..aeb4449 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"
> @@ -795,7 +799,7 @@ static const char *synth_field_fmt(char *type)
>   	else if (strcmp(type, "pid_t") == 0)
>   		fmt = "%d";
>   	else if (strcmp(type, "gfp_t") == 0)
> -		fmt = "%u";
> +		fmt = "%x";
>   	else if (synth_field_is_string(type))
>   		fmt = "%s";
>   
> @@ -838,9 +842,20 @@ 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++;
>   		}
>   	}

--
Zhengjun Xing