Re: [PATCH v2] tracing: Add verbose gfp_flag printing to synthetic events

[Xing Zhengjun]

Hi Tom,

On 7/11/2019 11:42 PM, Tom Zanussi wrote:

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.)

Thanks. I will send v3 version patch soon.

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 <zanu...@kernel.org>
Signed-off-by: Zhengjun Xing <zhengjun.x...@linux.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++;
                }
        }

--
Zhengjun Xing