diffcore-delta: make the hash a bit denser.

Junio C Hamano · Junio C Hamano · commit 2821104db7fa · 2006-03-12T17:26:32.000-08:00
To reduce wasted memory, wait until the hash fills up more
densely before we rehash.  This reduces the working set size a
bit further.

Signed-off-by: Junio C Hamano &lt;junkio@cox.net&gt;
diff --git a/diffcore-delta.c b/diffcore-delta.c
@@ -25,8 +25,12 @@
  */
 
 /* Wild guess at the initial hash size */
-#define INITIAL_HASH_SIZE 10
+#define INITIAL_HASH_SIZE 9
 #define HASHBASE 65537 /* next_prime(2^16) */
+/* We leave more room in smaller hash but do not let it
+ * grow to have unused hole too much.
+ */
+#define INITIAL_FREE(sz_log2) ((1<<(sz_log2))*(sz_log2-3)/(sz_log2))
 
 struct spanhash {
 	unsigned long hashval;
@@ -38,7 +42,8 @@ struct spanhash_top {
 	struct spanhash data[FLEX_ARRAY];
 };
 
-static struct spanhash *spanhash_find(struct spanhash_top *top, unsigned long hashval)
+static struct spanhash *spanhash_find(struct spanhash_top *top,
+				      unsigned long hashval)
 {
 	int sz = 1 << top->alloc_log2;
 	int bucket = hashval & (sz - 1);
@@ -62,7 +67,7 @@ static struct spanhash_top *spanhash_rehash(struct spanhash_top *orig)
 
 	new = xmalloc(sizeof(*orig) + sizeof(struct spanhash) * sz);
 	new->alloc_log2 = orig->alloc_log2 + 1;
-	new->free = osz;
+	new->free = INITIAL_FREE(new->alloc_log2);
 	memset(new->data, 0, sizeof(struct spanhash) * sz);
 	for (i = 0; i < osz; i++) {
 		struct spanhash *o = &(orig->data[i]);
@@ -122,7 +127,7 @@ static struct spanhash_top *hash_chars(unsigned char *buf, unsigned long sz)
 	i = INITIAL_HASH_SIZE;
 	hash = xmalloc(sizeof(*hash) + sizeof(struct spanhash) * (1<<i));
 	hash->alloc_log2 = i;
-	hash->free = (1<<i)/2;
+	hash->free = INITIAL_FREE(i);
 	memset(hash->data, 0, sizeof(struct spanhash) * (1<<i));
 
 	/* an 8-byte shift register made of accum1 and accum2.  New
diff --git a/diffcore-rename.c b/diffcore-rename.c
@@ -307,8 +307,8 @@ void diffcore_rename(struct diff_options *options)
 			m->score = estimate_similarity(one, two,
 						       minimum_score);
 		}
-		free(two->cnt_data);
-		two->cnt_data = NULL;
+		/* We do not need the text anymore */
+		diff_free_filespec_data(two);
 		dst_cnt++;
 	}
 	/* cost matrix sorted by most to least similar pair */

Original file line number	Diff line number	Diff line change
`@@ -307,8 +307,8 @@ void diffcore_rename(struct diff_options *options)`
`307`	`307`	`m->score = estimate_similarity(one, two,`
`308`	`308`	`minimum_score);`
`309`	`309`	`}`
`310`		`- free(two->cnt_data);`
`311`		`- two->cnt_data = NULL;`
	`310`	`+ /* We do not need the text anymore */`
	`311`	`+ diff_free_filespec_data(two);`
`312`	`312`	`dst_cnt++;`
`313`	`313`	`}`
`314`	`314`	`/* cost matrix sorted by most to least similar pair */`