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pcloudsgitster
pclouds
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gc: add --keep-largest-pack option
This adds a new repack mode that combines everything into a secondary pack, leaving the largest pack alone. This could help reduce memory pressure. On linux-2.6.git, valgrind massif reports 1.6GB heap in "pack all" case, and 535MB in "pack all except the base pack" case. We save roughly 1GB memory by excluding the base pack. This should also lower I/O because we don't have to rewrite a giant pack every time (e.g. for linux-2.6.git that's a 1.4GB pack file).. PS. The use of string_list here seems overkill, but we'll need it in the next patch... Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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‎Documentation/git-gc.txt‎

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@ git-gc - Cleanup unnecessary files and optimize the local repository
99
SYNOPSIS
1010
--------
1111
[verse]
12-
'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force]
12+
'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
1313

1414
DESCRIPTION
1515
-----------
@@ -84,6 +84,10 @@ be performed as well.
8484
Force `git gc` to run even if there may be another `git gc`
8585
instance running on this repository.
8686

87+
--keep-largest-pack::
88+
All packs except the largest pack and those marked with a
89+
`.keep` files are consolidated into a single pack.
90+
8791
Configuration
8892
-------------
8993

‎builtin/gc.c‎

Lines changed: 41 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -166,6 +166,22 @@ static int too_many_loose_objects(void)
166166
return needed;
167167
}
168168

169+
static void find_base_packs(struct string_list *packs)
170+
{
171+
struct packed_git *p, *base = NULL;
172+
173+
for (p = get_packed_git(the_repository); p; p = p->next) {
174+
if (!p->pack_local)
175+
continue;
176+
if (!base || base->pack_size < p->pack_size) {
177+
base = p;
178+
}
179+
}
180+
181+
if (base)
182+
string_list_append(packs, base->pack_name);
183+
}
184+
169185
static int too_many_packs(void)
170186
{
171187
struct packed_git *p;
@@ -188,7 +204,13 @@ static int too_many_packs(void)
188204
return gc_auto_pack_limit < cnt;
189205
}
190206

191-
static void add_repack_all_option(void)
207+
static int keep_one_pack(struct string_list_item *item, void *data)
208+
{
209+
argv_array_pushf(&repack, "--keep-pack=%s", basename(item->string));
210+
return 0;
211+
}
212+
213+
static void add_repack_all_option(struct string_list *keep_pack)
192214
{
193215
if (prune_expire && !strcmp(prune_expire, "now"))
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argv_array_push(&repack, "-a");
@@ -197,6 +219,9 @@ static void add_repack_all_option(void)
197219
if (prune_expire)
198220
argv_array_pushf(&repack, "--unpack-unreachable=%s", prune_expire);
199221
}
222+
223+
if (keep_pack)
224+
for_each_string_list(keep_pack, keep_one_pack, NULL);
200225
}
201226

202227
static void add_repack_incremental_option(void)
@@ -220,7 +245,7 @@ static int need_to_gc(void)
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* there is no need.
221246
*/
222247
if (too_many_packs())
223-
add_repack_all_option();
248+
add_repack_all_option(NULL);
224249
else if (too_many_loose_objects())
225250
add_repack_incremental_option();
226251
else
@@ -354,6 +379,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
354379
const char *name;
355380
pid_t pid;
356381
int daemonized = 0;
382+
int keep_base_pack = -1;
357383

358384
struct option builtin_gc_options[] = {
359385
OPT__QUIET(&quiet, N_("suppress progress reporting")),
@@ -366,6 +392,8 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
366392
OPT_BOOL_F(0, "force", &force,
367393
N_("force running gc even if there may be another gc running"),
368394
PARSE_OPT_NOCOMPLETE),
395+
OPT_BOOL(0, "keep-largest-pack", &keep_base_pack,
396+
N_("repack all other packs except the largest pack")),
369397
OPT_END()
370398
};
371399

@@ -431,8 +459,17 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
431459
*/
432460
daemonized = !daemonize();
433461
}
434-
} else
435-
add_repack_all_option();
462+
} else {
463+
struct string_list keep_pack = STRING_LIST_INIT_NODUP;
464+
465+
if (keep_base_pack != -1) {
466+
if (keep_base_pack)
467+
find_base_packs(&keep_pack);
468+
}
469+
470+
add_repack_all_option(&keep_pack);
471+
string_list_clear(&keep_pack, 0);
472+
}
436473

437474
name = lock_repo_for_gc(force, &pid);
438475
if (name) {

‎t/t6500-gc.sh‎

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -43,6 +43,31 @@ test_expect_success 'gc is not aborted due to a stale symref' '
4343
)
4444
'
4545

46+
test_expect_success 'gc --keep-largest-pack' '
47+
test_create_repo keep-pack &&
48+
(
49+
cd keep-pack &&
50+
test_commit one &&
51+
test_commit two &&
52+
test_commit three &&
53+
git gc &&
54+
( cd .git/objects/pack && ls *.pack ) >pack-list &&
55+
test_line_count = 1 pack-list &&
56+
BASE_PACK=.git/objects/pack/pack-*.pack &&
57+
test_commit four &&
58+
git repack -d &&
59+
test_commit five &&
60+
git repack -d &&
61+
( cd .git/objects/pack && ls *.pack ) >pack-list &&
62+
test_line_count = 3 pack-list &&
63+
git gc --keep-largest-pack &&
64+
( cd .git/objects/pack && ls *.pack ) >pack-list &&
65+
test_line_count = 2 pack-list &&
66+
test_path_is_file $BASE_PACK &&
67+
git fsck
68+
)
69+
'
70+
4671
test_expect_success 'auto gc with too many loose objects does not attempt to create bitmaps' '
4772
test_config gc.auto 3 &&
4873
test_config gc.autodetach false &&

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