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SubjectRe: [PATCH] trace:add "gfp_t" support in synthetic_events
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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@linux.intel.com>
>> ---
>> 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@kernel.org>
> ---
> 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

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