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tracing: Add hist trigger support for stacktraces as keys
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It's often useful to be able to use a stacktrace as a hash key, for
keeping a count of the number of times a particular call path resulted
in a trace event, for instance.  Add a special key named 'stacktrace'
which can be used as key in a 'keys=' param for this purpose:

    # echo hist:keys=stacktrace ... \
               [ if filter] > event/trigger

Link: http://lkml.kernel.org/r/87515e90b3785232a874a12156174635a348edb1.1457029949.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@tzanussi @rostedt
tzanussi authored and rostedt committed Apr 19, 2016
1 parent 3169619 commit 69a0200
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Showing 2 changed files with 109 additions and 42 deletions.
16 changes: 8 additions & 8 deletions kernel/trace/trace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3843,14 +3843,14 @@ static const char readme_msg[] =
"\t table using the key(s) and value(s) named, and the value of a\n"
"\t sum called 'hitcount' is incremented. Keys and values\n"
"\t correspond to fields in the event's format description. Keys\n"
"\t can be any field. Compound keys consisting of up to two\n"
"\t fields can be specified by the 'keys' keyword. Values must\n"
"\t correspond to numeric fields. Sort keys consisting of up to\n"
"\t two fields can be specified using the 'sort' keyword. The\n"
"\t sort direction can be modified by appending '.descending' or\n"
"\t '.ascending' to a sort field. The 'size' parameter can be\n"
"\t used to specify more or fewer than the default 2048 entries\n"
"\t for the hashtable size.\n\n"
"\t can be any field, or the special string 'stacktrace'.\n"
"\t Compound keys consisting of up to two fields can be specified\n"
"\t by the 'keys' keyword. Values must correspond to numeric\n"
"\t fields. Sort keys consisting of up to two fields can be\n"
"\t specified using the 'sort' keyword. The sort direction can\n"
"\t be modified by appending '.descending' or '.ascending' to a\n"
"\t sort field. The 'size' parameter can be used to specify more\n"
"\t or fewer than the default 2048 entries for the hashtable size.\n\n"
"\t Reading the 'hist' file for the event will dump the hash\n"
"\t table in its entirety to stdout. The default format used to\n"
"\t display a given field can be modified by appending any of the\n"
Expand Down
135 changes: 101 additions & 34 deletions kernel/trace/trace_events_hist.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,11 @@ struct hist_field {
unsigned int offset;
};

static u64 hist_field_none(struct hist_field *field, void *event)
{
return 0;
}

static u64 hist_field_counter(struct hist_field *field, void *event)
{
return 1;
Expand Down Expand Up @@ -73,8 +78,12 @@ DEFINE_HIST_FIELD_FN(u8);
#define for_each_hist_key_field(i, hist_data) \
for ((i) = (hist_data)->n_vals; (i) < (hist_data)->n_fields; (i)++)

#define HIST_STACKTRACE_DEPTH 16
#define HIST_STACKTRACE_SIZE (HIST_STACKTRACE_DEPTH * sizeof(unsigned long))
#define HIST_STACKTRACE_SKIP 5

#define HITCOUNT_IDX 0
#define HIST_KEY_SIZE_MAX (MAX_FILTER_STR_VAL + sizeof(u64))
#define HIST_KEY_SIZE_MAX (MAX_FILTER_STR_VAL + HIST_STACKTRACE_SIZE)

enum hist_field_flags {
HIST_FIELD_FL_HITCOUNT = 1,
Expand All @@ -85,6 +94,7 @@ enum hist_field_flags {
HIST_FIELD_FL_SYM_OFFSET = 32,
HIST_FIELD_FL_EXECNAME = 64,
HIST_FIELD_FL_SYSCALL = 128,
HIST_FIELD_FL_STACKTRACE = 256,
};

struct hist_trigger_attrs {
Expand Down Expand Up @@ -323,6 +333,11 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
goto out;
}

if (flags & HIST_FIELD_FL_STACKTRACE) {
hist_field->fn = hist_field_none;
goto out;
}

if (is_string_field(field)) {
flags |= HIST_FIELD_FL_STRING;
hist_field->fn = hist_field_string;
Expand Down Expand Up @@ -456,41 +471,46 @@ 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;

if (WARN_ON(key_idx >= TRACING_MAP_FIELDS_MAX))
return -EINVAL;

flags |= HIST_FIELD_FL_KEY;

field_name = strsep(&field_str, ".");
if (field_str) {
if (strcmp(field_str, "hex") == 0)
flags |= HIST_FIELD_FL_HEX;
else if (strcmp(field_str, "sym") == 0)
flags |= HIST_FIELD_FL_SYM;
else if (strcmp(field_str, "sym-offset") == 0)
flags |= HIST_FIELD_FL_SYM_OFFSET;
else if ((strcmp(field_str, "execname") == 0) &&
(strcmp(field_name, "common_pid") == 0))
flags |= HIST_FIELD_FL_EXECNAME;
else if (strcmp(field_str, "syscall") == 0)
flags |= HIST_FIELD_FL_SYSCALL;
else {
if (strcmp(field_str, "stacktrace") == 0) {
flags |= HIST_FIELD_FL_STACKTRACE;
key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
} else {
char *field_name = strsep(&field_str, ".");

if (field_str) {
if (strcmp(field_str, "hex") == 0)
flags |= HIST_FIELD_FL_HEX;
else if (strcmp(field_str, "sym") == 0)
flags |= HIST_FIELD_FL_SYM;
else if (strcmp(field_str, "sym-offset") == 0)
flags |= HIST_FIELD_FL_SYM_OFFSET;
else if ((strcmp(field_str, "execname") == 0) &&
(strcmp(field_name, "common_pid") == 0))
flags |= HIST_FIELD_FL_EXECNAME;
else if (strcmp(field_str, "syscall") == 0)
flags |= HIST_FIELD_FL_SYSCALL;
else {
ret = -EINVAL;
goto out;
}
}

field = trace_find_event_field(file->event_call, field_name);
if (!field) {
ret = -EINVAL;
goto out;
}
}

field = trace_find_event_field(file->event_call, field_name);
if (!field) {
ret = -EINVAL;
goto out;
key_size = field->size;
}

key_size = field->size;

hist_data->fields[key_idx] = create_hist_field(field, flags);
if (!hist_data->fields[key_idx]) {
ret = -ENOMEM;
Expand Down Expand Up @@ -679,7 +699,9 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)

field = hist_field->field;

if (is_string_field(field))
if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
cmp_fn = tracing_map_cmp_none;
else if (is_string_field(field))
cmp_fn = tracing_map_cmp_string;
else
cmp_fn = tracing_map_cmp_num(field->size,
Expand Down Expand Up @@ -786,7 +808,9 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
static void event_hist_trigger(struct event_trigger_data *data, void *rec)
{
struct hist_trigger_data *hist_data = data->private_data;
unsigned long entries[HIST_STACKTRACE_DEPTH];
char compound_key[HIST_KEY_SIZE_MAX];
struct stack_trace stacktrace;
struct hist_field *key_field;
struct tracing_map_elt *elt;
u64 field_contents;
Expand All @@ -799,15 +823,27 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
for_each_hist_key_field(i, hist_data) {
key_field = hist_data->fields[i];

field_contents = key_field->fn(key_field, rec);
if (key_field->flags & HIST_FIELD_FL_STRING)
key = (void *)(unsigned long)field_contents;
else
key = (void *)&field_contents;
if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
stacktrace.max_entries = HIST_STACKTRACE_DEPTH;
stacktrace.entries = entries;
stacktrace.nr_entries = 0;
stacktrace.skip = HIST_STACKTRACE_SKIP;

if (hist_data->n_keys > 1) {
memcpy(compound_key + key_field->offset, key,
key_field->size);
memset(stacktrace.entries, 0, HIST_STACKTRACE_SIZE);
save_stack_trace(&stacktrace);

key = entries;
} else {
field_contents = key_field->fn(key_field, rec);
if (key_field->flags & HIST_FIELD_FL_STRING)
key = (void *)(unsigned long)field_contents;
else
key = (void *)&field_contents;

if (hist_data->n_keys > 1) {
memcpy(compound_key + key_field->offset, key,
key_field->size);
}
}
}

Expand All @@ -819,13 +855,32 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec)
hist_trigger_elt_update(hist_data, elt, rec);
}

static void hist_trigger_stacktrace_print(struct seq_file *m,
unsigned long *stacktrace_entries,
unsigned int max_entries)
{
char str[KSYM_SYMBOL_LEN];
unsigned int spaces = 8;
unsigned int i;

for (i = 0; i < max_entries; i++) {
if (stacktrace_entries[i] == ULONG_MAX)
return;

seq_printf(m, "%*c", 1 + spaces, ' ');
sprint_symbol(str, stacktrace_entries[i]);
seq_printf(m, "%s\n", str);
}
}

static void
hist_trigger_entry_print(struct seq_file *m,
struct hist_trigger_data *hist_data, void *key,
struct tracing_map_elt *elt)
{
struct hist_field *key_field;
char str[KSYM_SYMBOL_LEN];
bool multiline = false;
unsigned int i;
u64 uval;

Expand Down Expand Up @@ -867,6 +922,12 @@ hist_trigger_entry_print(struct seq_file *m,

seq_printf(m, "%s: %-30s[%3llu]",
key_field->field->name, syscall_name, uval);
} else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
seq_puts(m, "stacktrace:\n");
hist_trigger_stacktrace_print(m,
key + key_field->offset,
HIST_STACKTRACE_DEPTH);
multiline = true;
} else if (key_field->flags & HIST_FIELD_FL_STRING) {
seq_printf(m, "%s: %-50s", key_field->field->name,
(char *)(key + key_field->offset));
Expand All @@ -877,7 +938,10 @@ hist_trigger_entry_print(struct seq_file *m,
}
}

seq_puts(m, " }");
if (!multiline)
seq_puts(m, " ");

seq_puts(m, "}");

seq_printf(m, " hitcount: %10llu",
tracing_map_read_sum(elt, HITCOUNT_IDX));
Expand Down Expand Up @@ -1021,7 +1085,10 @@ static int event_hist_trigger_print(struct seq_file *m,
if (i > hist_data->n_vals)
seq_puts(m, ",");

hist_field_print(m, key_field);
if (key_field->flags & HIST_FIELD_FL_STACKTRACE)
seq_puts(m, "stacktrace");
else
hist_field_print(m, key_field);
}

seq_puts(m, ":vals=");
Expand Down

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