Git's object store and packing are optimized for * Expensive repo to repo bandwidth; and * Small-ish files This justifies extensive use of compression.
In a multi-developer *office* with inter-repository transfers occurring over a 100Mb+ LAN, there is less reason to compress files and slow down response times. Response times suffer even more when large files are involved. However, *off-line* pack compression may still be desirable to reduce storage space.
Consequently, for such a usage pattern it is useful to specify different compression levels for loose objects and packs. This patch implements a config variable pack.compression in addition to the existing core.compression, meant to be used for repacking. It also adds --compression=N to pack-objects, meant for push/pull/fetch, if different, or if different on a per-repository basis.
** THIS PATCH IS UNTESTED AND MEANT FOR DISCUSSION. ** git-repack.sh might also need to be modified, and how to pass --compression=N during push/pull/fetch has not been investigated.
This applies on top of the git-repack --max-pack-size patchset.
Signed-off-by: Dana L. How <danahow@gmail.com> --- builtin-pack-objects.c | 56 ++++++++++++++++++++++++++++++++++++------------ 1 files changed, 42 insertions(+), 14 deletions(-)
Show changes to builtin-pack-objects.c +42 −14
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c index 69fec34..b663c15 100644 --- a/builtin-pack-objects.c +++ b/builtin-pack-objects.c @@ -70,6 +70,7 @@ static uint32_t pack_size_limit; static int pack_to_stdout; static int num_preferred_base; static struct progress progress_state; +static int pack_compression_level, pack_compression_seen; /* * The object names in objects array are hashed with this hashtable, @@ -414,6 +415,16 @@ static unsigned long write_object(struct sha1file *f, /* write limit if limited packsize and not first object */ unsigned long limit = pack_size_limit && nr_written ? pack_size_limit - write_offset : 0; + /* no if no delta */ + int usable_delta = !entry->delta ? 0 : + /* yes if unlimited packfile */ + !pack_size_limit ? 1 : + /* no if base written to previous pack */ + entry->delta->offset == (off_t)-1 ? 0 : + /* otherwise double-check written to this + * pack, like we do below + */ + entry->delta->offset ? 1 : 0; if (!pack_to_stdout) crc32_begin(f); @@ -423,8 +434,7 @@ static unsigned long write_object(struct sha1file *f, to_reuse = 0; /* can't reuse what we don't have */ else if (obj_type == OBJ_REF_DELTA || obj_type == OBJ_OFS_DELTA) /* check_object() decided it for us ... */ - to_reuse = !pack_size_limit || - (entry->delta->offset && entry->delta->offset != (off_t)-1); + to_reuse = usable_delta; /* ... but pack split may override that */ else if (obj_type != entry->in_pack_type) to_reuse = 0; /* pack has delta which is unusable */ @@ -435,6 +445,10 @@ static unsigned long write_object(struct sha1file *f, * and we do not need to deltify it. */ + /* differing core & pack compression when loose object -> must recompress */ + if (!entry->in_pack && pack_compression_level != zlib_compression_level) + to_reuse = 0; + else if (!entry->in_pack && !entry->delta) { unsigned char *map; unsigned long mapsize; @@ -462,16 +476,6 @@ static unsigned long write_object(struct sha1file *f, z_stream stream; unsigned long maxsize; void *out; - /* no if no delta */ - int usable_delta = !entry->delta ? 0 : - /* yes if unlimited packfile */ - !pack_size_limit ? 1 : - /* no if base written to previous pack */ - entry->delta->offset == (off_t)-1 ? 0 : - /* otherwise double-check written to this - * pack, like we do below - */ - entry->delta->offset ? 1 : 0; buf = read_sha1_file(entry->sha1, &type, &size); if (!buf) die("unable to read %s", sha1_to_hex(entry->sha1)); @@ -493,7 +497,7 @@ static unsigned long write_object(struct sha1file *f, } /* compress the data to store and put compressed length in datalen */ memset(&stream, 0, sizeof(stream)); - deflateInit(&stream, zlib_compression_level); + deflateInit(&stream, pack_compression_level); maxsize = deflateBound(&stream, size); out = xmalloc(maxsize); /* Compress it */ @@ -606,7 +610,7 @@ static unsigned long write_object(struct sha1file *f, unuse_pack(&w_curs); reused++; } - if (entry->delta) + if (usable_delta) written_delta++; written++; if (!pack_to_stdout) @@ -1622,6 +1626,16 @@ static int git_pack_config(const char *k, const char *v) window = git_config_int(k, v); return 0; } + if (!strcmp(k, "pack.compression")) { + int level = git_config_int(k, v); + if (level == -1) + level = Z_DEFAULT_COMPRESSION; + else if (level < 0 || level > Z_BEST_COMPRESSION) + die("bad pack compression level %d", level); + pack_compression_level = level; + pack_compression_seen = 1; + return 0; + } return git_default_config(k, v); } @@ -1732,6 +1746,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) rp_ac = 2; git_config(git_pack_config); + if (!pack_compression_seen) + pack_compression_level = zlib_compression_level; progress = isatty(2); for (i = 1; i < argc; i++) { @@ -1759,6 +1775,18 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix) usage(pack_usage); continue; } + if (!prefixcmp(arg, "--compression=")) { + char *end; + int level = strtoul(arg+14, &end, 0); + if (!arg[14] || *end) + usage(pack_usage); + if (level == -1) + level = Z_DEFAULT_COMPRESSION; + else if (level < 0 || level > Z_BEST_COMPRESSION) + die("bad pack compression level %d", level); + pack_compression_level = level; + continue; + } if (!prefixcmp(arg, "--window=")) { char *end; window = strtoul(arg+9, &end, 0);
-- 1.5.2.rc0.787.g0014
