[RFC][PATCH 11/21] tracing: Add variable support to hist triggers

From: Tom Zanussi
Date: Wed Feb 08 2017 - 12:31:37 EST

Add support for saving the value of a current event's event field by
assigning it to a variable that can be read by a subsequent event.

The basic syntax for saving a variable is to simply prefix a unique
variable name not corresponding to any keyword along with an '=' sign
to any event field.

Both keys and values can be saved and retrieved in this way:

# echo 'hist:keys=next_pid:vals=ts0=common_timestamp ...
# echo 'hist:key=timer_pid=common_pid ...'

If a variable isn't a key variable or prefixed with 'vals=', the
associated event field will be saved in a variable but won't be summed
as a value:

# echo 'hist:keys=next_pid:ts1=common_timestamp:...

Multiple variables can be assigned at the same time:

# echo 'hist:keys=pid:vals=ts0=common_timestamp,b=field1,field2 ...

Variables set as above can be used by being referenced from another
event, as described in a subsequent patch.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
kernel/trace/trace_events_hist.c | 160 ++++++++++++++++++++++++++++++++-------
1 file changed, 131 insertions(+), 29 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 8d7f7dd..e707577 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -29,6 +29,7 @@ typedef u64 (*hist_field_fn_t) (struct hist_field *field, void *event,
struct ring_buffer_event *rbe);

#define HIST_FIELD_OPERANDS_MAX 2
+#define HIST_ASSIGNMENT_MAX 4

struct hist_field {
struct ftrace_event_field *field;
@@ -36,8 +37,10 @@ struct hist_field {
hist_field_fn_t fn;
unsigned int size;
unsigned int offset;
- unsigned int is_signed;
+ unsigned int is_signed;
struct hist_field *operands[HIST_FIELD_OPERANDS_MAX];
+ u64 var_val;
+ char *var_name;
};

static u64 hist_field_none(struct hist_field *field, void *event,
@@ -140,12 +143,16 @@ enum hist_field_flags {
HIST_FIELD_FL_SYSCALL = 128,
HIST_FIELD_FL_STACKTRACE = 256,
HIST_FIELD_FL_LOG2 = 512,
- HIST_FIELD_FL_TIMESTAMP = 1024,
+ HIST_FIELD_FL_VAR = 1024,
+ HIST_FIELD_FL_VAR_ONLY = 2048,
+ HIST_FIELD_FL_TIMESTAMP = 4096,
};

struct hist_trigger_attrs {
char *keys_str;
char *vals_str;
+ char *assignment_str[HIST_ASSIGNMENT_MAX];
+ unsigned int n_assignments;
char *sort_key_str;
char *name;
bool pause;
@@ -241,9 +248,14 @@ static int parse_map_size(char *str)

static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
{
+ unsigned int i;
+
if (!attrs)
return;

+ for (i = 0; i < attrs->n_assignments; i++)
+ kfree(attrs->assignment_str[i]);
+
kfree(attrs->name);
kfree(attrs->sort_key_str);
kfree(attrs->keys_str);
@@ -258,9 +270,9 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
if ((strncmp(str, "key=", strlen("key=")) == 0) ||
(strncmp(str, "keys=", strlen("keys=")) == 0))
attrs->keys_str = kstrdup(str, GFP_KERNEL);
- else if ((strncmp(str, "val=", strlen("val=")) == 0) ||
- (strncmp(str, "vals=", strlen("vals=")) == 0) ||
- (strncmp(str, "values=", strlen("values=")) == 0))
+ else if (((strncmp(str, "val=", strlen("val=")) == 0) ||
+ (strncmp(str, "vals=", strlen("vals=")) == 0) ||
+ (strncmp(str, "values=", strlen("values=")) == 0)))
attrs->vals_str = kstrdup(str, GFP_KERNEL);
else if (strncmp(str, "sort=", strlen("sort=")) == 0)
attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
@@ -274,8 +286,22 @@ static int parse_assignment(char *str, struct hist_trigger_attrs *attrs)
goto out;
}
attrs->map_bits = map_bits;
- } else
- ret = -EINVAL;
+ } else {
+ char *assignment;
+
+ if (attrs->n_assignments == HIST_ASSIGNMENT_MAX) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ assignment = kstrdup(str, GFP_KERNEL);
+ if (!assignment) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ attrs->assignment_str[attrs->n_assignments++] = assignment;
+ }
out:
return ret;
}
@@ -398,11 +424,14 @@ static void destroy_hist_field(struct hist_field *hist_field)
for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
destroy_hist_field(hist_field->operands[i]);

+ kfree(hist_field->var_name);
+
kfree(hist_field);
}

static struct hist_field *create_hist_field(struct ftrace_event_field *field,
- unsigned long flags)
+ unsigned long flags,
+ char *var_name)
{
struct hist_field *hist_field;

@@ -427,7 +456,7 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
if (flags & HIST_FIELD_FL_LOG2) {
unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
hist_field->fn = hist_field_log2;
- hist_field->operands[0] = create_hist_field(field, fl);
+ hist_field->operands[0] = create_hist_field(field, fl, NULL);
hist_field->size = hist_field->operands[0]->size;
goto out;
}
@@ -461,6 +490,8 @@ static struct hist_field *create_hist_field(struct ftrace_event_field *field,
out:
hist_field->field = field;
hist_field->flags = flags;
+ if (var_name)
+ hist_field->var_name = kstrdup(var_name, GFP_KERNEL);

return hist_field;
}
@@ -480,7 +511,7 @@ static void destroy_hist_fields(struct hist_trigger_data *hist_data)
static int create_hitcount_val(struct hist_trigger_data *hist_data)
{
hist_data->fields[HITCOUNT_IDX] =
- create_hist_field(NULL, HIST_FIELD_FL_HITCOUNT);
+ create_hist_field(NULL, HIST_FIELD_FL_HITCOUNT, NULL);
if (!hist_data->fields[HITCOUNT_IDX])
return -ENOMEM;

@@ -495,16 +526,29 @@ static int create_hitcount_val(struct hist_trigger_data *hist_data)
static int create_val_field(struct hist_trigger_data *hist_data,
unsigned int val_idx,
struct trace_event_file *file,
- char *field_str)
+ char *field_str, char *var_name)
{
struct ftrace_event_field *field = NULL;
+ char *field_name, *token;
unsigned long flags = 0;
- char *field_name;
int ret = 0;

if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX))
return -EINVAL;

+ if (var_name)
+ flags |= HIST_FIELD_FL_VAR | HIST_FIELD_FL_VAR_ONLY;
+
+ token = strsep(&field_str, "=");
+ if (field_str) {
+ if (var_name) {
+ ret = -EINVAL;
+ goto out;
+ }
+ var_name = token;
+ flags |= HIST_FIELD_FL_VAR;
+ }
+
field_name = strsep(&field_str, ".");
if (field_str) {
if (strcmp(field_str, "hex") == 0)
@@ -526,7 +570,7 @@ static int create_val_field(struct hist_trigger_data *hist_data,
}
}

- hist_data->fields[val_idx] = create_hist_field(field, flags);
+ hist_data->fields[val_idx] = create_hist_field(field, flags, var_name);
if (!hist_data->fields[val_idx]) {
ret = -ENOMEM;
goto out;
@@ -544,7 +588,7 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
struct trace_event_file *file)
{
char *fields_str, *field_str;
- unsigned int i, j;
+ unsigned int i, j = 1;
int ret;

ret = create_hitcount_val(hist_data);
@@ -555,10 +599,6 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
if (!fields_str)
goto out;

- strsep(&fields_str, "=");
- if (!fields_str)
- goto out;
-
for (i = 0, j = 1; i < TRACING_MAP_VALS_MAX &&
j < TRACING_MAP_VALS_MAX; i++) {
field_str = strsep(&fields_str, ",");
@@ -566,7 +606,7 @@ static int create_val_fields(struct hist_trigger_data *hist_data,
break;
if (strcmp(field_str, "hitcount") == 0)
continue;
- ret = create_val_field(hist_data, j++, file, field_str);
+ ret = create_val_field(hist_data, j++, file, field_str, NULL);
if (ret)
goto out;
}
@@ -585,6 +625,7 @@ 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 *var_name;
int ret = 0;

if (WARN_ON(key_idx >= TRACING_MAP_FIELDS_MAX))
@@ -592,6 +633,10 @@ static int create_key_field(struct hist_trigger_data *hist_data,

flags |= HIST_FIELD_FL_KEY;

+ var_name = strsep(&field_str, "=");
+ if (field_str)
+ flags |= HIST_FIELD_FL_VAR;
+
if (strcmp(field_str, "stacktrace") == 0) {
flags |= HIST_FIELD_FL_STACKTRACE;
key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
@@ -636,7 +681,7 @@ static int create_key_field(struct hist_trigger_data *hist_data,
}
}

- hist_data->fields[key_idx] = create_hist_field(field, flags);
+ hist_data->fields[key_idx] = create_hist_field(field, flags, var_name);
if (!hist_data->fields[key_idx]) {
ret = -ENOMEM;
goto out;
@@ -695,6 +740,31 @@ static int create_key_fields(struct hist_trigger_data *hist_data,
return ret;
}

+static int create_var_fields(struct hist_trigger_data *hist_data,
+ struct trace_event_file *file)
+{
+ unsigned int i, j = hist_data->n_vals;
+ char *str, *var;
+ int ret = 0;
+
+ for (i = 0; i < hist_data->attrs->n_assignments; i++) {
+
+ str = hist_data->attrs->assignment_str[i];
+
+ var = strsep(&str, "=");
+ if (!str) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = create_val_field(hist_data, j++, file, str, var);
+ if (ret)
+ goto out;
+ }
+ out:
+ return ret;
+}
+
static int create_hist_fields(struct hist_trigger_data *hist_data,
struct trace_event_file *file)
{
@@ -704,6 +774,10 @@ static int create_hist_fields(struct hist_trigger_data *hist_data,
if (ret)
goto out;

+ ret = create_var_fields(hist_data, file);
+ if (ret)
+ goto out;
+
ret = create_key_fields(hist_data, file);
if (ret)
goto out;
@@ -839,8 +913,7 @@ static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
idx = tracing_map_add_key_field(map,
hist_field->offset,
cmp_fn);
-
- } else
+ } else if (!(hist_field->flags & HIST_FIELD_FL_VAR))
idx = tracing_map_add_sum_field(map);

if (idx < 0)
@@ -931,6 +1004,11 @@ static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
for_each_hist_val_field(i, hist_data) {
hist_field = hist_data->fields[i];
hist_val = hist_field->fn(hist_field, rec, rbe);
+ if (hist_field->flags & HIST_FIELD_FL_VAR) {
+ hist_field->var_val = hist_val;
+ if (hist_field->flags & HIST_FIELD_FL_VAR_ONLY)
+ continue;
+ }
tracing_map_update_sum(elt, i, hist_val);
}
}
@@ -996,17 +1074,21 @@ static void event_hist_trigger(struct event_trigger_data *data, void *rec,
} else
key = (void *)&field_contents;
}
-
if (use_compound_key)
add_to_key(compound_key, key, key_field, rec);
+
+ if (key_field->flags & HIST_FIELD_FL_VAR)
+ key_field->var_val = (u64)key;
}

if (use_compound_key)
key = compound_key;

elt = tracing_map_insert(hist_data->map, key);
- if (elt)
- hist_trigger_elt_update(hist_data, elt, rec, rbe);
+ if (!elt)
+ return;
+
+ hist_trigger_elt_update(hist_data, elt, rec, rbe);
}

static void hist_trigger_stacktrace_print(struct seq_file *m,
@@ -1228,7 +1310,12 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
{
const char *field_name = hist_field_name(hist_field);

- seq_printf(m, "%s", field_name);
+ if (hist_field->var_name)
+ seq_printf(m, "%s=", hist_field->var_name);
+
+ if (field_name)
+ seq_printf(m, "%s", field_name);
+
if (hist_field->flags) {
const char *flags_str = get_hist_field_flags(hist_field);

@@ -1237,6 +1324,16 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
}
}

+static bool var_only(struct hist_trigger_data *hist_data)
+{
+ unsigned int i;
+
+ for_each_hist_val_field(i, hist_data)
+ if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR_ONLY)
+ return true;
+ return false;
+}
+
static int event_hist_trigger_print(struct seq_file *m,
struct event_trigger_ops *ops,
struct event_trigger_data *data)
@@ -1266,15 +1363,19 @@ static int event_hist_trigger_print(struct seq_file *m,
hist_field_print(m, key_field);
}

- seq_puts(m, ":vals=");
+ if (!var_only(hist_data))
+ seq_puts(m, ":vals=");
+ else
+ seq_puts(m, ":");

for_each_hist_val_field(i, hist_data) {
- if (i == HITCOUNT_IDX)
+ if (i == HITCOUNT_IDX && !var_only(hist_data))
seq_puts(m, "hitcount");
else if (hist_data->fields[i]->flags & HIST_FIELD_FL_TIMESTAMP)
seq_puts(m, "common_timestamp");
else {
- seq_puts(m, ",");
+ if (!var_only(hist_data))
+ seq_puts(m, ",");
hist_field_print(m, hist_data->fields[i]);
}
}
@@ -1673,6 +1774,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
}

ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file);
+
/*
* The above returns on success the # of triggers registered,
* but if it didn't register any it returns zero. Consider no
--
1.9.3