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From: Jeff King <>
Cc: Michael Haggerty <>,
	Junio C Hamano <>
Subject: [PATCH v2 5/7] pack-objects: break out of want_object loop early
Date: Fri, 29 Jul 2016 00:10:31 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

When pack-objects collects the list of objects to pack
(either from stdin, or via its internal rev-list), it
filters each one through want_object_in_pack().

This function loops through each existing packfile, looking
for the object. When we find it, we mark the pack/offset
combo for later use. However, we can't just return "yes, we
want it" at that point. If --honor-pack-keep is in effect,
we must keep looking to find it in _all_ packs, to make sure
none of them has a .keep. Likewise, if --local is in effect,
we must make sure it is not present in any non-local pack.

As a result, the sum effort of these calls is effectively
O(nr_objects * nr_packs). In an ordinary repository, we have
only a handful of packs, and this doesn't make a big
difference. But in pathological cases, it can slow the
counting phase to a crawl.

This patch notices the case that we have neither "--local"
nor "--honor-pack-keep" in effect and breaks out of the loop
early, after finding the first instance. Note that our worst
case is still "objects * packs" (i.e., we might find each
object in the last pack we look in), but in practice we will
often break out early. On an "average" repo, my git.git with
8 packs, this shows a modest 2% (a few dozen milliseconds)
improvement in the counting-objects phase of "git
pack-objects --all <foo" (hackily instrumented by sticking
exit(0) right after list_objects).

But in a much more pathological case, it makes a bigger
difference. I ran the same command on a real-world example
with ~9 million objects across 1300 packs. The counting time
dropped from 413s to 45s, an improvement of about 89%.

Note that this patch won't do anything by itself for a
normal "git gc", as it uses both --honor-pack-keep and

Signed-off-by: Jeff King <>
Same as earlier, though I took the re-ordering and comment from Junio
that came out of the earlier discussion.

 builtin/pack-objects.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index a2f8cfd..8ad11f2 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -977,6 +977,22 @@ static int want_object_in_pack(const unsigned char *sha1,
 				return 1;
 			if (incremental)
 				return 0;
+			/*
+			 * When asked to do --local (do not include an
+			 * object that appears in a pack we borrow
+			 * from elsewhere) or --honor-pack-keep (do not
+			 * include an object that appears in a pack marked
+			 * with .keep), we need to make sure no copy of this
+			 * object come from in _any_ pack that causes us to
+			 * omit it, and need to complete this loop.  When
+			 * neither option is in effect, we know the object
+			 * we just found is going to be packed, so break
+			 * out of the loop to return 1 now.
+			 */
+			if (!ignore_packed_keep && !local)
+				break;
 			if (local && !p->pack_local)
 				return 0;
 			if (ignore_packed_keep && p->pack_local && p->pack_keep)

  parent reply	other threads:[~2016-07-29  4:10 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-29  4:04 [PATCH v2 0/7] speed up pack-objects counting with many packs Jeff King
2016-07-29  4:06 ` [PATCH v2 1/7] t/perf: add tests for many-pack scenarios Jeff King
2016-07-29  4:06 ` [PATCH v2 2/7] sha1_file: drop free_pack_by_name Jeff King
2016-07-29  4:06 ` [PATCH v2 3/7] add generic most-recently-used list Jeff King
2016-07-29  4:09 ` [PATCH v2 4/7] find_pack_entry: replace last_found_pack with MRU cache Jeff King
2016-07-29  4:10 ` Jeff King [this message]
2016-07-29  4:11 ` [PATCH v2 6/7] pack-objects: compute local/ignore_pack_keep early Jeff King
2016-07-29  4:15 ` [PATCH v2 7/7] pack-objects: use mru list when iterating over packs Jeff King
2016-07-29  5:45   ` Jeff King
2016-07-29 15:02     ` Junio C Hamano
2016-08-08 14:50       ` Jeff King
2016-08-08 16:28         ` Junio C Hamano
2016-08-08 16:51           ` Jeff King
2016-08-08 17:16             ` Junio C Hamano
2016-08-09 14:04               ` Jeff King
2016-08-09 17:45                 ` Jeff King
2016-08-09 18:06                   ` Junio C Hamano
2016-08-09 22:29                 ` Junio C Hamano
2016-08-10 11:52                   ` [PATCH v3 0/2] pack-objects mru Jeff King
2016-08-10 12:02                     ` [PATCH v3 1/2] pack-objects: break delta cycles before delta-search phase Jeff King
2016-08-10 20:17                       ` Junio C Hamano
2016-08-11  5:02                         ` Jeff King
2016-08-11  5:15                           ` [PATCH v4 " Jeff King
2016-08-11  6:57                           ` [PATCH v3 " Jeff King
2016-08-11  9:20                             ` [PATCH v5] pack-objects mru Jeff King
2016-08-11  9:24                               ` [PATCH v5 1/4] provide an initializer for "struct object_info" Jeff King
2016-08-11  9:25                               ` [PATCH v5 2/4] sha1_file: make packed_object_info public Jeff King
2016-08-11  9:26                               ` [PATCH v5 3/4] pack-objects: break delta cycles before delta-search phase Jeff King
2016-08-11  9:26                               ` [PATCH v5 4/4] pack-objects: use mru list when iterating over packs Jeff King
2016-08-11  9:57                               ` [PATCH v5] pack-objects mru Jeff King
2016-08-11 15:11                                 ` Junio C Hamano
2016-08-11 16:19                                   ` Jeff King
2016-08-10 12:03                     ` [PATCH v3 2/2] pack-objects: use mru list when iterating over packs Jeff King
2016-08-10 16:47                     ` [PATCH v3 0/2] pack-objects mru Junio C Hamano
2016-08-11  4:48                       ` Jeff King

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