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let pack-objects do the writing of unreachable objects as loose objects

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Commit ccc1297226 changed the behavior
of 'git repack -A' so unreachable objects are stored as loose objects.
However it did so in a naive and inn efficient way by making packs
about to be deleted inaccessible and feeding their content through
'git unpack-objects'.  While this works, there are major flaws with
this approach:

- It is unacceptably sloooooooooooooow.

  In the Linux kernel repository with no actual unreachable objects,
  doing 'git repack -A -d' before:

	real    2m33.220s
	user    2m21.675s
	sys     0m3.510s

  And with this change:

	real    0m36.849s
	user    0m24.365s
	sys     0m1.950s

  For reference, here's the timing for 'git repack -a -d':

	real    0m35.816s
	user    0m22.571s
	sys     0m2.011s

  This is explained by the fact that 'git unpack-objects' was used to
  unpack _every_ objects even if (almost) 100% of them were thrown away.

- There is a black out period.

  Between the removal of the .idx file for the redundant pack and the
  completion of its unpacking, the unreachable objects become completely
  unaccessible.  This is not a big issue as we're talking about unreachable
  objects, but some consistency is always good.

- There is no way to easily set a sensible mtime for the newly created
  unreachable loose objects.

So, while having a command called "pack-objects" to perform object
unpacking looks really odd, this is probably the best compromize to be
able to solve the above issues in an efficient way.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Nicolas Pitre
2008-05-14 01:33:53 -04:00
committed by Junio C Hamano
parent bbac73117e
commit ca11b212eb
2 changed files with 45 additions and 17 deletions
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40
builtin-pack-objects.c
View File

@ -28,7 +28,8 @@ git-pack-objects [{ -q | --progress | --all-progress }] \n\
[--window=N] [--window-memory=N] [--depth=N] \n\
[--no-reuse-delta] [--no-reuse-object] [--delta-base-offset] \n\
[--threads=N] [--non-empty] [--revs [--unpacked | --all]*] [--reflog] \n\
[--stdout | base-name] [--include-tag] [--keep-unreachable] \n\
[--stdout | base-name] [--include-tag] \n\
[--keep-unreachable | --unpack-unreachable] \n\
[<ref-list | <object-list]";
struct object_entry {
@ -65,7 +66,7 @@ static struct pack_idx_entry **written_list;
static uint32_t nr_objects, nr_alloc, nr_result, nr_written;
static int non_empty;
static int no_reuse_delta, no_reuse_object, keep_unreachable, include_tag;
static int no_reuse_delta, no_reuse_object, keep_unreachable, unpack_unreachable, include_tag;
static int local;
static int incremental;
static int allow_ofs_delta;
@ -1905,6 +1906,32 @@ static void add_objects_in_unpacked_packs(struct rev_info *revs)
free(in_pack.array);
}
static void loosen_unused_packed_objects(struct rev_info *revs)
{
struct packed_git *p;
uint32_t i;
const unsigned char *sha1;
for (p = packed_git; p; p = p->next) {
for (i = 0; i < revs->num_ignore_packed; i++) {
if (matches_pack_name(p, revs->ignore_packed[i]))
break;
}
if (revs->num_ignore_packed <= i)
continue;
if (open_pack_index(p))
die("cannot open pack index");
for (i = 0; i < p->num_objects; i++) {
sha1 = nth_packed_object_sha1(p, i);
if (!locate_object_entry(sha1))
if (force_object_loose(sha1, p->mtime))
die("unable to force loose object");
}
}
}
static void get_object_list(int ac, const char **av)
{
struct rev_info revs;
@ -1939,6 +1966,8 @@ static void get_object_list(int ac, const char **av)
if (keep_unreachable)
add_objects_in_unpacked_packs(&revs);
if (unpack_unreachable)
loosen_unused_packed_objects(&revs);
}
static int adjust_perm(const char *path, mode_t mode)
@ -2073,6 +2102,10 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
keep_unreachable = 1;
continue;
}
if (!strcmp("--unpack-unreachable", arg)) {
unpack_unreachable = 1;
continue;
}
if (!strcmp("--include-tag", arg)) {
include_tag = 1;
continue;
@ -2138,6 +2171,9 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
if (!pack_to_stdout && thin)
die("--thin cannot be used to build an indexable pack.");
if (keep_unreachable && unpack_unreachable)
die("--keep-unreachable and --unpack-unreachable are incompatible.");
#ifdef THREADED_DELTA_SEARCH
if (!delta_search_threads) /* --threads=0 means autodetect */
delta_search_threads = online_cpus();