1. Stefan Saasen
  2. git

Commits

Linus Torvalds  committed 304de2d

Avoid unnecessary strlen() calls

This is a micro-optimization that grew out of the mailing list discussion
about "strlen()" showing up in profiles.

We used to pass regular C strings around to the low-level tree walking
routines, and while this worked fine, it meant that we needed to call
strlen() on strings that the caller always actually knew the size of
anyway.

So pass the length of the string down wih the string, and avoid
unnecessary calls to strlen(). Also, when extracting a pathname from a
tree entry, use "tree_entry_len()" instead of strlen(), since the length
of the pathname is directly calculable from the decoded tree entry itself
without having to actually do another strlen().

This shaves off another ~5-10% from some loads that are very tree
intensive (notably doing commit filtering by a pathspec).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>"
Signed-off-by: Junio C Hamano <junkio@cox.net>

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  • Parent commits a0cba10
  • Branches master

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Files changed (3)

File tree-diff.c

View file
 #include "diff.h"
 #include "tree.h"
 
-static char *malloc_base(const char *base, const char *path, int pathlen)
+static char *malloc_base(const char *base, int baselen, const char *path, int pathlen)
 {
-	int baselen = strlen(base);
 	char *newbase = xmalloc(baselen + pathlen + 2);
 	memcpy(newbase, base, baselen);
 	memcpy(newbase + baselen, path, pathlen);
 }
 
 static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
-		       const char *base);
+		       const char *base, int baselen);
 
-static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
+static int compare_tree_entry(struct tree_desc *t1, struct tree_desc *t2, const char *base, int baselen, struct diff_options *opt)
 {
 	unsigned mode1, mode2;
 	const char *path1, *path2;
 	sha1 = tree_entry_extract(t1, &path1, &mode1);
 	sha2 = tree_entry_extract(t2, &path2, &mode2);
 
-	pathlen1 = strlen(path1);
-	pathlen2 = strlen(path2);
+	pathlen1 = tree_entry_len(path1, sha1);
+	pathlen2 = tree_entry_len(path2, sha2);
 	cmp = base_name_compare(path1, pathlen1, mode1, path2, pathlen2, mode2);
 	if (cmp < 0) {
-		show_entry(opt, "-", t1, base);
+		show_entry(opt, "-", t1, base, baselen);
 		return -1;
 	}
 	if (cmp > 0) {
-		show_entry(opt, "+", t2, base);
+		show_entry(opt, "+", t2, base, baselen);
 		return 1;
 	}
 	if (!opt->find_copies_harder && !hashcmp(sha1, sha2) && mode1 == mode2)
 	 * file, we need to consider it a remove and an add.
 	 */
 	if (S_ISDIR(mode1) != S_ISDIR(mode2)) {
-		show_entry(opt, "-", t1, base);
-		show_entry(opt, "+", t2, base);
+		show_entry(opt, "-", t1, base, baselen);
+		show_entry(opt, "+", t2, base, baselen);
 		return 0;
 	}
 
 	if (opt->recursive && S_ISDIR(mode1)) {
 		int retval;
-		char *newbase = malloc_base(base, path1, pathlen1);
+		char *newbase = malloc_base(base, baselen, path1, pathlen1);
 		if (opt->tree_in_recursive)
 			opt->change(opt, mode1, mode2,
 				    sha1, sha2, base, path1);
 	return 0;
 }
 
-static int interesting(struct tree_desc *desc, const char *base, struct diff_options *opt)
+static int interesting(struct tree_desc *desc, const char *base, int baselen, struct diff_options *opt)
 {
 	const char *path;
+	const unsigned char *sha1;
 	unsigned mode;
 	int i;
-	int baselen, pathlen;
+	int pathlen;
 
 	if (!opt->nr_paths)
 		return 1;
 
-	(void)tree_entry_extract(desc, &path, &mode);
+	sha1 = tree_entry_extract(desc, &path, &mode);
 
-	pathlen = strlen(path);
-	baselen = strlen(base);
+	pathlen = tree_entry_len(path, sha1);
 
 	for (i=0; i < opt->nr_paths; i++) {
 		const char *match = opt->paths[i];
 }
 
 /* A whole sub-tree went away or appeared */
-static void show_tree(struct diff_options *opt, const char *prefix, struct tree_desc *desc, const char *base)
+static void show_tree(struct diff_options *opt, const char *prefix, struct tree_desc *desc, const char *base, int baselen)
 {
 	while (desc->size) {
-		if (interesting(desc, base, opt))
-			show_entry(opt, prefix, desc, base);
+		if (interesting(desc, base, baselen, opt))
+			show_entry(opt, prefix, desc, base, baselen);
 		update_tree_entry(desc);
 	}
 }
 
 /* A file entry went away or appeared */
 static void show_entry(struct diff_options *opt, const char *prefix, struct tree_desc *desc,
-		       const char *base)
+		       const char *base, int baselen)
 {
 	unsigned mode;
 	const char *path;
 
 	if (opt->recursive && S_ISDIR(mode)) {
 		enum object_type type;
-		char *newbase = malloc_base(base, path, strlen(path));
+		int pathlen = tree_entry_len(path, sha1);
+		char *newbase = malloc_base(base, baselen, path, pathlen);
 		struct tree_desc inner;
 		void *tree;
 
 			die("corrupt tree sha %s", sha1_to_hex(sha1));
 
 		inner.buf = tree;
-		show_tree(opt, prefix, &inner, newbase);
+		show_tree(opt, prefix, &inner, newbase, baselen + 1 + pathlen);
 
 		free(tree);
 		free(newbase);
 
 int diff_tree(struct tree_desc *t1, struct tree_desc *t2, const char *base, struct diff_options *opt)
 {
+	int baselen = strlen(base);
+
 	while (t1->size | t2->size) {
-		if (opt->nr_paths && t1->size && !interesting(t1, base, opt)) {
+		if (opt->nr_paths && t1->size && !interesting(t1, base, baselen, opt)) {
 			update_tree_entry(t1);
 			continue;
 		}
-		if (opt->nr_paths && t2->size && !interesting(t2, base, opt)) {
+		if (opt->nr_paths && t2->size && !interesting(t2, base, baselen, opt)) {
 			update_tree_entry(t2);
 			continue;
 		}
 		if (!t1->size) {
-			show_entry(opt, "+", t2, base);
+			show_entry(opt, "+", t2, base, baselen);
 			update_tree_entry(t2);
 			continue;
 		}
 		if (!t2->size) {
-			show_entry(opt, "-", t1, base);
+			show_entry(opt, "-", t1, base, baselen);
 			update_tree_entry(t1);
 			continue;
 		}
-		switch (compare_tree_entry(t1, t2, base, opt)) {
+		switch (compare_tree_entry(t1, t2, base, baselen, opt)) {
 		case -1:
 			update_tree_entry(t1);
 			continue;

File tree-walk.c

View file
 static void entry_extract(struct tree_desc *t, struct name_entry *a)
 {
 	a->sha1 = tree_entry_extract(t, &a->path, &a->mode);
-	a->pathlen = strlen(a->path);
+	a->pathlen = tree_entry_len(a->path, a->sha1);
 }
 
 void update_tree_entry(struct tree_desc *desc)
 
 		sha1 = tree_entry_extract(t, &entry, mode);
 		update_tree_entry(t);
-		entrylen = strlen(entry);
+		entrylen = tree_entry_len(entry, sha1);
 		if (entrylen > namelen)
 			continue;
 		cmp = memcmp(name, entry, entrylen);

File tree-walk.h

View file
 	int pathlen;
 };
 
+static inline int tree_entry_len(const char *name, const unsigned char *sha1)
+{
+	return (char *)sha1 - (char *)name - 1;
+}
+
 void update_tree_entry(struct tree_desc *);
 const unsigned char *tree_entry_extract(struct tree_desc *, const char **, unsigned int *);