[git commit] modprobe: use hash table. speeds up significantly if modprobe.dep is large

[Denys Vlasenko]

commit: http://git.busybox.net/busybox/commit/?id=e12e0acb92329f95a77121f489b491d84b6a2c33
branch: http://git.busybox.net/busybox/commit/?id=refs/heads/master

function                                             old     new   delta
helper_get_module                                    106     157     +51
config_file_action                                   413     431     +18
modprobe_main                                        690     706     +16
do_modprobe                                          580     588      +8
add_probe                                             81      83      +2
load_modules_dep                                     192     190      -2
get_or_add_modentry                                   10       -     -10
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 5/1 up/down: 95/-12)             Total: 83 bytes

Signed-off-by: Timo Teras <timo.teras at iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 modutils/modprobe.c |   43 +++++++++++++++++++++++++++++--------------
 1 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/modutils/modprobe.c b/modutils/modprobe.c
index 678f4be..c1a1828 100644
--- a/modutils/modprobe.c
+++ b/modutils/modprobe.c
@@ -157,20 +157,21 @@ struct module_entry { /* I'll call it ME. */
 	llist_t *deps; /* strings. modules we depend on */
 };
 
+#define DB_HASH_SIZE 256
+
 struct globals {
-	llist_t *db; /* MEs of all modules ever seen (caching for speed) */
 	llist_t *probes; /* MEs of module(s) requested on cmdline */
 	char *cmdline_mopts; /* module options from cmdline */
 	int num_unresolved_deps;
 	/* bool. "Did we have 'symbol:FOO' requested on cmdline?" */
 	smallint need_symbols;
 	struct utsname uts;
+	llist_t *db[DB_HASH_SIZE]; /* MEs of all modules ever seen (caching for speed) */
 } FIX_ALIASING;
-#define G (*(struct globals*)&bb_common_bufsiz1)
-#define INIT_G() do { } while (0)
-struct BUG_G_too_big {
-	char BUG_G_too_big[sizeof(G) <= COMMON_BUFSIZE ? 1 : -1];
-};
+#define G (*ptr_to_globals)
+#define INIT_G() do { \
+        SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
+} while (0)
 
 
 static int read_config(const char *path);
@@ -190,14 +191,26 @@ static char *gather_options_str(char *opts, const char *append)
 	return opts;
 }
 
+/* These three functions called many times, optimizing for speed.
+ * Users reported minute-long delays when they runn iptables repeatedly
+ * (iptables use modprobe to install needed kernel modules).
+ */
 static struct module_entry *helper_get_module(const char *module, int create)
 {
 	char modname[MODULE_NAME_LEN];
 	struct module_entry *e;
 	llist_t *l;
+	unsigned i;
+	unsigned hash;
 
 	filename2modname(module, modname);
-	for (l = G.db; l != NULL; l = l->link) {
+
+	hash = 0;
+	for (i = 0; modname[i]; i++)
+		hash = ((hash << 5) + hash) + modname[i];
+	hash %= DB_HASH_SIZE;
+
+	for (l = G.db[hash]; l; l = l->link) {
 		e = (struct module_entry *) l->data;
 		if (strcmp(e->modname, modname) == 0)
 			return e;
@@ -207,15 +220,15 @@ static struct module_entry *helper_get_module(const char *module, int create)
 
 	e = xzalloc(sizeof(*e));
 	e->modname = xstrdup(modname);
-	llist_add_to(&G.db, e);
+	llist_add_to(&G.db[hash], e);
 
 	return e;
 }
-static struct module_entry *get_or_add_modentry(const char *module)
+static ALWAYS_INLINE struct module_entry *get_or_add_modentry(const char *module)
 {
 	return helper_get_module(module, 1);
 }
-static struct module_entry *get_modentry(const char *module)
+static ALWAYS_INLINE struct module_entry *get_modentry(const char *module)
 {
 	return helper_get_module(module, 0);
 }
@@ -275,7 +288,7 @@ static int FAST_FUNC config_file_action(const char *filename,
 				continue;
 			filename2modname(tokens[1], wildcard);
 
-			for (l = G.probes; l != NULL; l = l->link) {
+			for (l = G.probes; l; l = l->link) {
 				m = (struct module_entry *) l->data;
 				if (fnmatch(wildcard, m->modname, 0) != 0)
 					continue;
@@ -377,7 +390,6 @@ static char *parse_and_add_kcmdline_module_options(char *options, const char *mo
 static int do_modprobe(struct module_entry *m)
 {
 	int rc, first;
-	llist_t *l;
 
 	if (!(m->flags & MODULE_FLAG_FOUND_IN_MODDEP)) {
 		if (!(option_mask32 & INSMOD_OPT_SILENT))
@@ -390,8 +402,11 @@ static int do_modprobe(struct module_entry *m)
 	if (!(option_mask32 & OPT_REMOVE))
 		m->deps = llist_rev(m->deps);
 
-	for (l = m->deps; l != NULL; l = l->link)
-		DBG("dep: %s", l->data);
+	if (0) {
+		llist_t *l;
+		for (l = m->deps; l; l = l->link)
+			DBG("dep: %s", l->data);
+	}
 
 	first = 1;
 	rc = 0;
-- 
1.7.3.4