avoid repeated scans for goto targets (udev_iter_find_label)

The scans are now performed up-front at parse-time, instead of being
repeated for each event at run-time.

Cachegrind reports a 5% reduction in cpu cycles
(excluding the time spent in-kernel).

diff --git a/udev/udev_rules.c b/udev/udev_rules.c
index d4dcb0680158305602eaf70d82e2a9ebb7a98bd4..9c37571fb0ae358825a0c07193355873105e88f3 100644 (file)
--- a/udev/udev_rules.c
+++ b/udev/udev_rules.c
@@ -1529,7 +1529,7 @@ int udev_rules_get_name(struct udev_rules *rules, struct udevice *udevice)
 
                        if (rule->goto_label.operation != KEY_OP_UNSET) {
                                dbg(udevice->udev, "moving forward to label '%s'\n", key_val(rule, &rule->goto_label));
-                               udev_rules_iter_label(&iter, key_val(rule, &rule->goto_label));
+                               udev_rules_iter_goto(&iter, rule->goto_rule_off);
                        }
                }
        }
@@ -1609,7 +1609,7 @@ int udev_rules_get_run(struct udev_rules *rules, struct udevice *udevice)
 
                        if (rule->goto_label.operation != KEY_OP_UNSET) {
                                dbg(udevice->udev, "moving forward to label '%s'\n", key_val(rule, &rule->goto_label));
-                               udev_rules_iter_label(&iter, key_val(rule, &rule->goto_label));
+                               udev_rules_iter_goto(&iter, rule->goto_rule_off);
                        }
                }
        }

diff --git a/udev/udev_rules.h b/udev/udev_rules.h
index 02685e18342ec80d9071a8fb496f5c3c6f371138..af96b8119b22f0888623e206b84a14b613c2014a 100644 (file)
--- a/udev/udev_rules.h
+++ b/udev/udev_rules.h
@@ -84,6 +84,7 @@ struct udev_rule {
        struct key wait_for;
        struct key label;
        struct key goto_label;
+       size_t goto_rule_off;
 
        struct key name;
        struct key symlink;
@@ -122,7 +123,7 @@ extern void udev_rules_cleanup(struct udev_rules *rules);
 
 extern void udev_rules_iter_init(struct udev_rules_iter *iter, struct udev_rules *rules);
 extern struct udev_rule *udev_rules_iter_next(struct udev_rules_iter *iter);
-extern struct udev_rule *udev_rules_iter_label(struct udev_rules_iter *iter, const char *label);
+extern struct udev_rule *udev_rules_iter_goto(struct udev_rules_iter *iter, size_t rule_off);
 
 extern int udev_rules_get_name(struct udev_rules *rules, struct udevice *udev);
 extern int udev_rules_get_run(struct udev_rules *rules, struct udevice *udev);

diff --git a/udev/udev_rules_parse.c b/udev/udev_rules_parse.c
index 229096c8d77d6d6809aab1c41c8e924f8d7b1458..5a76889c841adeca8781214baf8bd3dc3b8004cc 100644 (file)
--- a/udev/udev_rules_parse.c
+++ b/udev/udev_rules_parse.c
@@ -58,29 +58,40 @@ struct udev_rule *udev_rules_iter_next(struct udev_rules_iter *iter)
        return rule;
 }
 
-struct udev_rule *udev_rules_iter_label(struct udev_rules_iter *iter, const char *label)
+struct udev_rule *udev_rules_iter_goto(struct udev_rules_iter *iter, size_t rule_off)
+{
+       struct udev_rules *rules = iter->rules;
+       struct udev_rule *rule;
+
+       dbg(rules->udev "current=%zi\n", iter->current);
+       iter->current = rule_off;
+       rule = (struct udev_rule *) (rules->buf + iter->current);
+
+       return rule;
+}
+
+static size_t find_label(const struct udev_rules_iter *iter, const char *label)
 {
        struct udev_rule *rule;
        struct udev_rules *rules = iter->rules;
-       size_t start = iter->current;
+       size_t current = iter->current;
 
 next:
-       dbg(rules->udev, "current=%zi\n", iter->current);
-       if (iter->current >= rules->bufsize) {
+       dbg(rules->udev, "current=%zi\n", current);
+       if (current >= rules->bufsize) {
                err(rules->udev, "LABEL='%s' not found, GOTO will be ignored\n", label);
-               iter->current = start;
-               return NULL;
+               return iter->current;
        }
-       rule = (struct udev_rule *) (rules->buf + iter->current);
+       rule = (struct udev_rule *) (rules->buf + current);
 
        if (strcmp(&rule->buf[rule->label.val_off], label) != 0) {
                dbg(rules->udev, "moving forward, looking for label '%s'\n", label);
-               iter->current += sizeof(struct udev_rule) + rule->bufsize;
+               current += sizeof(struct udev_rule) + rule->bufsize;
                goto next;
        }
 
        dbg(rules->udev, "found label '%s'\n", label);
-       return rule;
+       return current;
 }
 
 static int get_key(struct udev_rules *rules, char **line, char **key, enum key_operation *operation, char **value)
@@ -674,6 +685,11 @@ static int parse_file(struct udev_rules *rules, const char *filename)
        size_t cur;
        size_t count;
        int retval = 0;
+       size_t start;
+       struct udev_rule *rule;
+       struct udev_rules_iter iter;
+
+       start = rules->bufsize;
 
        if (file_map(filename, &buf, &bufsize) != 0) {
                err(rules->udev, "can't open '%s' as rules file: %s\n", filename, strerror(errno));
@@ -722,6 +738,22 @@ static int parse_file(struct udev_rules *rules, const char *filename)
                add_to_rules(rules, line, filename, lineno);
        }
 
+       /* Compute all goto targets within this file */
+       udev_rules_iter_init(&iter, rules);
+       udev_rules_iter_goto(&iter, start);
+       while((rule = udev_rules_iter_next(&iter))) {
+               if (rule->goto_label.operation != KEY_OP_UNSET) {
+                       char *goto_label = &rule->buf[rule->goto_label.val_off];
+
+                       dbg(rules->udev, "resolving goto label '%s'", goto_label);
+                       rule->goto_rule_off = find_label(&iter, goto_label);
+                       if (rule->goto_rule_off == iter.current) {
+                               err(rules->udev, "goto nonexistent label '%s' in '%s'",
+                                   goto_label, filename);
+                       }
+               }
+       }
+
        file_unmap(buf, bufsize);
        return retval;
 }