[PATCH v3 19/22] libtracefs: Allow for simple SQL statements to create a histogram
From: Steven Rostedt
Date: Tue Aug 03 2021 - 13:06:44 EST
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Allow tracefs_sql() to take a simple select statement without the
JOIN .. ON clause, that will simply update the start event. This, along
with tracefs_synth_get_start_hist(), will allow a user to utilize
tracefs_sql() to create a synthetic event.
Link: https://lore.kernel.org/linux-rt-users/YQakDYRnId+bK+ue@lx-t490/
Suggested-by: Ahmed S. Darwish <a.darwish@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
Documentation/libtracefs-sql.txt | 27 +++++-
include/tracefs-local.h | 3 +
src/sqlhist.y | 11 ++-
src/tracefs-hist.c | 60 +++++++++----
src/tracefs-sqlhist.c | 144 +++++++++++++++++++++++++++++--
5 files changed, 216 insertions(+), 29 deletions(-)
diff --git a/Documentation/libtracefs-sql.txt b/Documentation/libtracefs-sql.txt
index e10a22cd531b..ee8d5c1d63c7 100644
--- a/Documentation/libtracefs-sql.txt
+++ b/Documentation/libtracefs-sql.txt
@@ -32,6 +32,8 @@ to attach two events together and form another event (table). Utilizing the
SQL *SELECT* *FROM* *JOIN* *ON* [ *WHERE* ] syntax, a synthetic event can easily
be created from two different events.
+For simple SQL queries to make a histogram instead of a synthetic event, see
+HISTOGRAMS below.
*tracefs_sql*() takes in a *tep* handler (See _tep_local_events_(3)) that is used to
verify the events within the _sql_buffer_ expression. The _name_ is the name of the
@@ -160,6 +162,12 @@ select start.pid, (end.TIMESTAMP_USECS - start.TIMESTAMP_USECS) as lat from sche
WHERE start.prio < 100 || end.prev_prio < 100
--
+HISTOGRAMS
+----------
+
+Simple SQL statements without the *JOIN* *ON* may also be used, which will create a histogram
+instead. When doing this, the struct tracefs_hist descriptor can be retrieved from the
+returned synthetic event descriptor via the *tracefs_synth_get_start_hist*(3).
RETURN VALUE
------------
@@ -243,9 +251,22 @@ static int do_sql(const char *buffer, const char *name,
exit(-1);
}
- tracefs_synth_show(&seq, NULL, synth);
- if (execute)
- tracefs_synth_create(NULL, synth);
+ if (tracefs_synth_complete(synth)) {
+ tracefs_synth_show(&seq, NULL, synth);
+ if (execute)
+ tracefs_synth_create(NULL, synth);
+ } else {
+ struct tracefs_hist *hist;
+ hist = tracefs_synth_get_start_hist(synth);
+ if (!hist) {
+ perror("get_start_hist");
+ exit(-1);
+ }
+ tracefs_hist_show(&seq, NULL, hist, 0);
+ if (execute)
+ tracefs_hist_start(NULL, hist);
+ }
+
tracefs_synth_free(synth);
trace_seq_do_printf(&seq);
diff --git a/include/tracefs-local.h b/include/tracefs-local.h
index 41fbcc0faa95..09288aeac521 100644
--- a/include/tracefs-local.h
+++ b/include/tracefs-local.h
@@ -85,4 +85,7 @@ int trace_append_filter(char **filter, unsigned int *state,
enum tracefs_compare compare,
const char *val);
+struct tracefs_synth *synth_init_from(struct tep_handle *tep,
+ const char *start_system,
+ const char *start_event);
#endif /* _TRACE_FS_LOCAL_H */
diff --git a/src/sqlhist.y b/src/sqlhist.y
index 9d03a457ae84..d5cbecc7bf92 100644
--- a/src/sqlhist.y
+++ b/src/sqlhist.y
@@ -63,7 +63,7 @@ extern void yyerror(struct sqlhist_bison *, char *fmt, ...);
%type <string> name label
-%type <expr> selection_expr field item named_field join_clause
+%type <expr> selection_expr field item named_field
%type <expr> selection_addition
%type <expr> compare compare_list compare_cmds compare_items
%type <expr> compare_and_or
@@ -202,8 +202,13 @@ opt_where_clause :
| where_clause
;
+opt_join_clause :
+ /* empty set */
+ | join_clause
+ ;
+
table_exp :
- from_clause join_clause opt_where_clause
+ from_clause opt_join_clause opt_where_clause
;
from_clause :
@@ -222,7 +227,7 @@ from_clause :
;
join_clause :
- JOIN item ON match_clause { add_to(sb, $2); }
+ JOIN item ON match_clause { add_to(sb, $2); }
;
match :
diff --git a/src/tracefs-hist.c b/src/tracefs-hist.c
index 305e3e720341..301abc255d5f 100644
--- a/src/tracefs-hist.c
+++ b/src/tracefs-hist.c
@@ -724,6 +724,33 @@ static int add_var(char ***list, const char *name, const char *var, bool is_var)
return 0;
}
+__hidden struct tracefs_synth *
+synth_init_from(struct tep_handle *tep, const char *start_system,
+ const char *start_event_name)
+{
+ struct tep_event *start_event;
+ struct tracefs_synth *synth;
+
+ start_event = tep_find_event_by_name(tep, start_system,
+ start_event_name);
+ if (!start_event) {
+ errno = ENODEV;
+ return NULL;
+ }
+
+ synth = calloc(1, sizeof(*synth));
+ if (!synth)
+ return NULL;
+
+ synth->start_event = start_event;
+
+ /* Hold onto a reference to this handler */
+ tep_ref(tep);
+ synth->tep = tep;
+
+ return synth;
+}
+
/**
* tracefs_synth_init - create a new tracefs_synth instance
* @tep: The tep handle that holds the events to work on
@@ -778,7 +805,6 @@ struct tracefs_synth *tracefs_synth_init(struct tep_handle *tep,
const char *end_match_field,
const char *match_name)
{
- struct tep_event *start_event;
struct tep_event *end_event;
struct tracefs_synth *synth;
int ret = 0;
@@ -789,25 +815,18 @@ struct tracefs_synth *tracefs_synth_init(struct tep_handle *tep,
return NULL;
}
- start_event = tep_find_event_by_name(tep, start_system,
- start_event_name);
- if (!start_event) {
- errno = ENODEV;
+ synth = synth_init_from(tep, start_system, start_event_name);
+ if (!synth)
return NULL;
- }
end_event = tep_find_event_by_name(tep, end_system,
end_event_name);
if (!end_event) {
+ tep_unref(tep);
errno = ENODEV;
return NULL;
}
- synth = calloc(1, sizeof(*synth));
- if (!synth)
- return NULL;
-
- synth->start_event = start_event;
synth->end_event = end_event;
synth->name = strdup(name);
@@ -815,10 +834,6 @@ struct tracefs_synth *tracefs_synth_init(struct tep_handle *tep,
ret = tracefs_synth_add_match_field(synth, start_match_field,
end_match_field, match_name);
- /* Hold onto a reference to this handler */
- tep_ref(tep);
- synth->tep = tep;
-
if (!synth->name || !synth->start_keys || !synth->end_keys || ret) {
tracefs_synth_free(synth);
synth = NULL;
@@ -1458,6 +1473,11 @@ int tracefs_synth_create(struct tracefs_instance *instance,
return -1;
}
+ if (!synth->name || !synth->end_event) {
+ errno = EUNATCH;
+ return -1;
+ }
+
if (verify_state(synth) < 0)
return -1;
@@ -1540,6 +1560,11 @@ int tracefs_synth_destroy(struct tracefs_instance *instance,
return -1;
}
+ if (!synth->name || !synth->end_event) {
+ errno = EUNATCH;
+ return -1;
+ }
+
/* Try to disable the event if possible */
tracefs_event_disable(instance, "synthetic", synth->name);
@@ -1596,6 +1621,11 @@ int tracefs_synth_show(struct trace_seq *seq,
return -1;
}
+ if (!synth->name || !synth->end_event) {
+ errno = EUNATCH;
+ return -1;
+ }
+
synthetic_event = create_synthetic_event(synth);
if (!synthetic_event)
return -1;
diff --git a/src/tracefs-sqlhist.c b/src/tracefs-sqlhist.c
index 81a0cd1a908b..d9ebe2eab411 100644
--- a/src/tracefs-sqlhist.c
+++ b/src/tracefs-sqlhist.c
@@ -678,6 +678,70 @@ static int update_vars(struct tep_handle *tep,
return 0;
}
+/*
+ * Called when there's a FROM but no JOIN(to), which means that the
+ * selections can be fields and not mention the event itself.
+ */
+static int update_fields(struct tep_handle *tep,
+ struct sql_table *table,
+ struct expr *expr)
+{
+ struct field *event_field = &expr->field;
+ struct sqlhist_bison *sb = table->sb;
+ struct tep_format_field *tfield;
+ struct tep_event *event;
+ struct field *field;
+ const char *p;
+ int len;
+
+ /* First update fields with aliases an such and add event */
+ update_vars(tep, table, expr);
+
+ /*
+ * If event is not found, the creation of the synth will
+ * add a proper error, so return "success".
+ */
+ if (!event_field->event)
+ return 0;
+
+ event = event_field->event;
+
+ for_each_field(expr, field, table) {
+ const char *field_name;
+
+ field = &expr->field;
+
+ if (field->event)
+ continue;
+
+ field_name = field->raw;
+
+ p = strchr(field_name, '.');
+ if (p) {
+ len = p - field_name;
+ p = strndup(field_name, len);
+ if (!p)
+ return -1;
+ field_name = store_str(sb, p);
+ if (!field_name)
+ return -1;
+ free((char *)p);
+ }
+
+ tfield = tep_find_any_field(event, field_name);
+ /* Let it error properly later */
+ if (!tfield)
+ continue;
+
+ field->system = event_field->system;
+ field->event_name = event_field->event_name;
+ field->event = event;
+ field->field = field_name;
+ }
+
+ return 0;
+}
+
static int match_error(struct sqlhist_bison *sb, struct match *match,
struct field *lmatch, struct field *rmatch)
{
@@ -1153,6 +1217,42 @@ static void compare_error(struct tep_handle *tep,
compare->lval->field.raw, compare->rval->field.raw);
}
+static void compare_no_to_error(struct sqlhist_bison *sb, struct expr *expr)
+{
+ struct compare *compare = &expr->compare;
+
+ sb->line_no = compare->lval->line;
+ sb->line_idx = compare->lval->idx;
+
+ parse_error(sb, compare->lval->field.raw,
+ "Simple SQL (without JOIN/ON) do not allow comparisons\n",
+ compare->lval->field.raw, compare->rval->field.raw);
+}
+
+static void where_no_to_error(struct sqlhist_bison *sb, struct expr *expr,
+ const char *from_event, const char *event)
+{
+ while (expr) {
+ switch (expr->filter.type) {
+ case FILTER_OR:
+ case FILTER_AND:
+ case FILTER_GROUP:
+ case FILTER_NOT_GROUP:
+ expr = expr->filter.lval;
+ continue;
+ default:
+ break;
+ }
+ break;
+ }
+ sb->line_no = expr->filter.lval->line;
+ sb->line_idx = expr->filter.lval->idx;
+
+ parse_error(sb, expr->filter.lval->field.raw,
+ "Event '%s' does not match FROM event '%s'\n",
+ event, from_event);
+}
+
static struct tracefs_synth *build_synth(struct tep_handle *tep,
const char *name,
struct sql_table *table)
@@ -1171,17 +1271,35 @@ static struct tracefs_synth *build_synth(struct tep_handle *tep,
bool started_end = false;
int ret;
- if (!table->to || !table->from)
+ if (!table->from)
return NULL;
- ret = update_vars(tep, table, table->to);
+ /* This could be a simple SQL statement to only build a histogram */
+ if (!table->to) {
+ ret = update_fields(tep, table, table->from);
+ if (ret < 0)
+ return NULL;
+
+ start_system = table->from->field.system;
+ start_event = table->from->field.event_name;
+
+ synth = synth_init_from(tep, start_system, start_event);
+ if (!synth)
+ return synth_init_error(tep, table);
+ goto hist_only;
+ }
+
+ ret = update_vars(tep, table, table->from);
if (ret < 0)
return NULL;
- ret = update_vars(tep, table, table->from);
+ ret = update_vars(tep, table, table->to);
if (ret < 0)
return NULL;
+ start_system = table->from->field.system;
+ start_event = table->from->field.event_name;
+
match = table->matches;
if (!match)
return NULL;
@@ -1190,9 +1308,6 @@ static struct tracefs_synth *build_synth(struct tep_handle *tep,
if (ret < 0)
return NULL;
- start_system = table->from->field.system;
- start_event = table->from->field.event_name;
-
end_system = table->to->field.system;
end_event = table->to->field.event_name;
@@ -1222,14 +1337,18 @@ static struct tracefs_synth *build_synth(struct tep_handle *tep,
}
}
+ hist_only:
+ /* table->to may be NULL here */
+
for (expr = table->selections; expr; expr = expr->next) {
if (expr->type == EXPR_FIELD) {
+ ret = -1;
field = &expr->field;
if (field->system == start_system &&
field->event_name == start_event) {
ret = tracefs_synth_add_start_field(synth,
field->field, field->label);
- } else {
+ } else if (table->to) {
ret = tracefs_synth_add_end_field(synth,
field->field, field->label);
}
@@ -1240,6 +1359,11 @@ static struct tracefs_synth *build_synth(struct tep_handle *tep,
continue;
}
+ if (!table->to) {
+ compare_no_to_error(table->sb, expr);
+ goto free;
+ }
+
if (expr->type != EXPR_COMPARE)
goto free;
@@ -1267,7 +1391,11 @@ static struct tracefs_synth *build_synth(struct tep_handle *tep,
if (start)
started = &started_start;
- else
+ else if (!table->to) {
+ where_no_to_error(table->sb, expr, start_event,
+ filter_event);
+ goto free;
+ } else
started = &started_end;
ret = build_filter(tep, table->sb, synth, start, expr, started);
--
2.30.2