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[PATCH 10/11] object: try 3-way cuckoo

From
Junio C Hamano <gitster@pobox.com>
Date
Aug 11, 2011, 17:53 UTC
Message-ID
<1313085196-13249-11-git-send-email-gitster@pobox.com>
In-Reply-To
<1313085196-13249-1-git-send-email-gitster@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
../+v/48b49262cd2d0d64696b489fe5bdfa8efb9180f5/git-pack-objects
Counting objects: 2139209, done.
30.68user 2.26system 0:33.05elapsed 99%CPU (0avgtext+0avgdata 3660832maxresident)k
0inputs+0outputs (0major+421963minor)pagefaults 0swaps
Counting objects: 2139209, done.
30.76user 2.26system 0:33.12elapsed 99%CPU (0avgtext+0avgdata 3660480maxresident)k
0inputs+0outputs (0major+421941minor)pagefaults 0swaps
Counting objects: 2139209, done.
30.74user 2.33system 0:33.18elapsed 99%CPU (0avgtext+0avgdata 3661696maxresident)k
0inputs+0outputs (0major+422017minor)pagefaults 0swaps
---
 object.c |   15 ++++-----------
 1 files changed, 4 insertions(+), 11 deletions(-)
diff --git a/object.c b/object.c
index caced56..18e6bcf 100644
--- a/object.c
+++ b/object.c
@@ -49,20 +49,18 @@ struct object *get_indexed_object(unsigned int idx)
 struct object *lookup_object(const unsigned char *sha1)
 {
 	struct object *obj;
-	unsigned int hashval[4];
+	unsigned int hashval[3];
 
 	if (!obj_hash)
 		return NULL;
 
-	memcpy(hashval, sha1, 16);
+	memcpy(hashval, sha1, 12);
 	if ((obj = obj_hash[H(hashval, 0)]) && !hashcmp(sha1, obj->sha1))
 		return obj;
 	if ((obj = obj_hash[H(hashval, 1)]) && !hashcmp(sha1, obj->sha1))
 		return obj;
 	if ((obj = obj_hash[H(hashval, 2)]) && !hashcmp(sha1, obj->sha1))
 		return obj;
-	if ((obj = obj_hash[H(hashval, 3)]) && !hashcmp(sha1, obj->sha1))
-		return obj;
 	return NULL;
 }
 
@@ -82,9 +80,9 @@ static struct object *insert_obj_hash(struct object *obj)
 	for (loop = obj_hash_size / 2; 0 <= loop; loop--) {
 		struct object *tmp_obj;
 		unsigned int ix;
-		unsigned int hashval[4];
+		unsigned int hashval[3];
 
-		memcpy(hashval, obj->sha1, 16);
+		memcpy(hashval, obj->sha1, 12);
 		ix = H(hashval, 0);
 		if (!obj_hash[ix]) {
 			obj_hash[ix] = obj;
@@ -96,11 +94,6 @@ static struct object *insert_obj_hash(struct object *obj)
 			return NULL;
 		}
 		ix = H(hashval, 2);
-		if (!obj_hash[ix]) {
-			obj_hash[ix] = obj;
-			return NULL;
-		}
-		ix = H(hashval, 3);
 		tmp_obj = obj_hash[ix];
 		obj_hash[ix] = obj;
 		if (!tmp_obj)
-- 
1.7.6.433.g1421f
Previous: Junio C HamanoNext: Junio C Hamano
Message 11 of 15 in “Micro-optimizing lookup_object()”
  1. 00/11 Micro-optimizing lookup_object()Junio C Hamano, Aug 11, 2011
  2. 01/11 object.c: code movement for readabilityJunio C Hamano, Aug 11, 2011
  3. 02/11 object.c: remove duplicated code for object hashingJunio C Hamano, Aug 11, 2011
  4. 03/11 pack-objects --count-onlyJunio C Hamano, Aug 11, 2011
  5. 04/11 object: next_size() helper for readabilityJunio C Hamano, Aug 11, 2011
  6. 05/11 object hash: we know the table size is a power of twoJunio C Hamano, Aug 11, 2011
  7. 06/11 object: growing the hash-table more aggressively does not help muchJunio C Hamano, Aug 11, 2011
  8. 07/11 object: try naive cuckoo hashingJunio C Hamano, Aug 11, 2011
  9. 08/11 object: try 5-way cuckoo -- use all 20-bytes of SHA-1Junio C Hamano, Aug 11, 2011
  10. 09/11 object: try 4-way cuckooJunio C Hamano, Aug 11, 2011
  11. 10/11 object: try 3-way cuckooJunio C Hamano, Aug 11, 2011
  12. 11/11 object: try 2-way cuckoo againJunio C Hamano, Aug 11, 2011
  13. 12/11 object.c: make object hash implementation more opaqueJunio C Hamano, Aug 11, 2011
  14. git_checkattr() is inefficient when repeated [Re: [PATCH 00/11] Micro-optimizing lookup_object()]Thomas Rast, Aug 12, 2011
  15. Junio C HamanoAug 15, 2011

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