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Merge branch 'jc/pack-reuse'

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* jc/pack-reuse:
  pack-objects: avoid delta chains that are too long.
  git-repack: allow passing a couple of flags to pack-objects.
  pack-objects: finishing touches.
  pack-objects: reuse data from existing packs.
This commit is contained in:
Junio C Hamano 2006-02-21 22:38:43 -08:00
commit 155d12912f
6 changed files with 441 additions and 72 deletions
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21
Documentation/git-pack-objects.txt
View File

@ -8,7 +8,10 @@ git-pack-objects - Create a packed archive of objects.
SYNOPSIS
--------
'git-pack-objects' [--non-empty] [--local] [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list
[verse]
'git-pack-objects' [-q] [--no-reuse-delta] [--non-empty]
[--local] [--incremental] [--window=N] [--depth=N]
{--stdout | base-name} < object-list
DESCRIPTION
@ -32,6 +35,10 @@ Placing both in the pack/ subdirectory of $GIT_OBJECT_DIRECTORY (or
any of the directories on $GIT_ALTERNATE_OBJECT_DIRECTORIES)
enables git to read from such an archive.
In a packed archive, an object is either stored as a compressed
whole, or as a difference from some other object. The latter is
often called a delta.
OPTIONS
-------
@ -74,6 +81,18 @@ base-name::
Only create a packed archive if it would contain at
least one object.
-q::
This flag makes the command not to report its progress
on the standard error stream.
--no-reuse-delta::
When creating a packed archive in a repository that
has existing packs, the command reuses existing deltas.
This sometimes results in a slightly suboptimal pack.
This flag tells the command not to reuse existing deltas
but compute them from scratch.
Author
------
Written by Linus Torvalds <torvalds@osdl.org>

10
Documentation/git-repack.txt
View File

@ -9,7 +9,7 @@ objects into pack files.
SYNOPSIS
--------
'git-repack' [-a] [-d] [-l] [-n]
'git-repack' [-a] [-d] [-f] [-l] [-n] [-q]
DESCRIPTION
-----------
@ -43,6 +43,14 @@ OPTIONS
Pass the `--local` option to `git pack-objects`, see
gitlink:git-pack-objects[1].
-f::
Pass the `--no-reuse-delta` option to `git pack-objects`, see
gitlink:git-pack-objects[1].
-q::
Pass the `-q` option to `git pack-objects`, see
gitlink:git-pack-objects[1].
-n::
Do not update the server information with
`git update-server-info`.

13
git-repack.sh
View File

@ -3,17 +3,20 @@
# Copyright (c) 2005 Linus Torvalds
#
USAGE='[-a] [-d] [-l] [-n]'
USAGE='[-a] [-d] [-f] [-l] [-n] [-q]'
. git-sh-setup
no_update_info= all_into_one= remove_redundant= local=
no_update_info= all_into_one= remove_redundant=
local= quiet= no_reuse_delta=
while case "$#" in 0) break ;; esac
do
case "$1" in
-n) no_update_info=t ;;
-a) all_into_one=t ;;
-d) remove_redundant=t ;;
-l) local=t ;;
-q) quiet=-q ;;
-f) no_reuse_delta=--no-reuse-delta ;;
-l) local=--local ;;
*) usage ;;
esac
shift
@ -39,9 +42,7 @@ case ",$all_into_one," in
find . -type f \( -name '*.pack' -o -name '*.idx' \) -print`
;;
esac
if [ "$local" ]; then
pack_objects="$pack_objects --local"
fi
pack_objects="$pack_objects $local $quiet $no_reuse_delta"
name=$(git-rev-list --objects $rev_list $(git-rev-parse $rev_parse) 2>&1 |
git-pack-objects --non-empty $pack_objects .tmp-pack) ||
exit 1

382
pack-objects.c
View File

@ -5,21 +5,45 @@
#include "csum-file.h"
#include <sys/time.h>
static const char pack_usage[] = "git-pack-objects [-q] [--non-empty] [--local] [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list";
static const char pack_usage[] = "git-pack-objects [-q] [--no-reuse-delta] [--non-empty] [--local] [--incremental] [--window=N] [--depth=N] {--stdout | base-name} < object-list";
struct object_entry {
unsigned char sha1[20];
unsigned long size;
unsigned long offset;
unsigned int depth;
unsigned int hash;
unsigned long size; /* uncompressed size */
unsigned long offset; /* offset into the final pack file;
* nonzero if already written.
*/
unsigned int depth; /* delta depth */
unsigned int delta_limit; /* base adjustment for in-pack delta */
unsigned int hash; /* name hint hash */
enum object_type type;
unsigned long delta_size;
struct object_entry *delta;
enum object_type in_pack_type; /* could be delta */
unsigned long delta_size; /* delta data size (uncompressed) */
struct object_entry *delta; /* delta base object */
struct packed_git *in_pack; /* already in pack */
unsigned int in_pack_offset;
struct object_entry *delta_child; /* delitified objects who bases me */
struct object_entry *delta_sibling; /* other deltified objects who
* uses the same base as me
*/
};
/*
* Objects we are going to pack are colected in objects array (dynamically
* expanded). nr_objects & nr_alloc controls this array. They are stored
* in the order we see -- typically rev-list --objects order that gives us
* nice "minimum seek" order.
*
* sorted-by-sha ans sorted-by-type are arrays of pointers that point at
* elements in the objects array. The former is used to build the pack
* index (lists object names in the ascending order to help offset lookup),
* and the latter is used to group similar things together by try_delta()
* heuristics.
*/
static unsigned char object_list_sha1[20];
static int non_empty = 0;
static int no_reuse_delta = 0;
static int local = 0;
static int incremental = 0;
static struct object_entry **sorted_by_sha, **sorted_by_type;
@ -29,6 +53,137 @@ static const char *base_name;
static unsigned char pack_file_sha1[20];
static int progress = 1;
/*
* The object names in objects array are hashed with this hashtable,
* to help looking up the entry by object name. Binary search from
* sorted_by_sha is also possible but this was easier to code and faster.
* This hashtable is built after all the objects are seen.
*/
static int *object_ix = NULL;
static int object_ix_hashsz = 0;
/*
* Pack index for existing packs give us easy access to the offsets into
* corresponding pack file where each object's data starts, but the entries
* do not store the size of the compressed representation (uncompressed
* size is easily available by examining the pack entry header). We build
* a hashtable of existing packs (pack_revindex), and keep reverse index
* here -- pack index file is sorted by object name mapping to offset; this
* pack_revindex[].revindex array is an ordered list of offsets, so if you
* know the offset of an object, next offset is where its packed
* representation ends.
*/
struct pack_revindex {
struct packed_git *p;
unsigned long *revindex;
} *pack_revindex = NULL;
static int pack_revindex_hashsz = 0;
/*
* stats
*/
static int written = 0;
static int written_delta = 0;
static int reused = 0;
static int reused_delta = 0;
static int pack_revindex_ix(struct packed_git *p)
{
unsigned int ui = (unsigned int) p;
int i;
ui = ui ^ (ui >> 16); /* defeat structure alignment */
i = (int)(ui % pack_revindex_hashsz);
while (pack_revindex[i].p) {
if (pack_revindex[i].p == p)
return i;
if (++i == pack_revindex_hashsz)
i = 0;
}
return -1 - i;
}
static void prepare_pack_ix(void)
{
int num;
struct packed_git *p;
for (num = 0, p = packed_git; p; p = p->next)
num++;
if (!num)
return;
pack_revindex_hashsz = num * 11;
pack_revindex = xcalloc(sizeof(*pack_revindex), pack_revindex_hashsz);
for (p = packed_git; p; p = p->next) {
num = pack_revindex_ix(p);
num = - 1 - num;
pack_revindex[num].p = p;
}
/* revindex elements are lazily initialized */
}
static int cmp_offset(const void *a_, const void *b_)
{
unsigned long a = *(unsigned long *) a_;
unsigned long b = *(unsigned long *) b_;
if (a < b)
return -1;
else if (a == b)
return 0;
else
return 1;
}
/*
* Ordered list of offsets of objects in the pack.
*/
static void prepare_pack_revindex(struct pack_revindex *rix)
{
struct packed_git *p = rix->p;
int num_ent = num_packed_objects(p);
int i;
void *index = p->index_base + 256;
rix->revindex = xmalloc(sizeof(unsigned long) * (num_ent + 1));
for (i = 0; i < num_ent; i++) {
long hl = *((long *)(index + 24 * i));
rix->revindex[i] = ntohl(hl);
}
/* This knows the pack format -- the 20-byte trailer
* follows immediately after the last object data.
*/
rix->revindex[num_ent] = p->pack_size - 20;
qsort(rix->revindex, num_ent, sizeof(unsigned long), cmp_offset);
}
static unsigned long find_packed_object_size(struct packed_git *p,
unsigned long ofs)
{
int num;
int lo, hi;
struct pack_revindex *rix;
unsigned long *revindex;
num = pack_revindex_ix(p);
if (num < 0)
die("internal error: pack revindex uninitialized");
rix = &pack_revindex[num];
if (!rix->revindex)
prepare_pack_revindex(rix);
revindex = rix->revindex;
lo = 0;
hi = num_packed_objects(p) + 1;
do {
int mi = (lo + hi) / 2;
if (revindex[mi] == ofs) {
return revindex[mi+1] - ofs;
}
else if (ofs < revindex[mi])
hi = mi;
else
lo = mi + 1;
} while (lo < hi);
die("internal error: pack revindex corrupt");
}
static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
{
unsigned long othersize, delta_size;
@ -78,35 +233,69 @@ static unsigned long write_object(struct sha1file *f, struct object_entry *entry
{
unsigned long size;
char type[10];
void *buf = read_sha1_file(entry->sha1, type, &size);
void *buf;
unsigned char header[10];
unsigned hdrlen, datalen;
enum object_type obj_type;
int to_reuse = 0;
obj_type = entry->type;
if (! entry->in_pack)
to_reuse = 0; /* can't reuse what we don't have */
else if (obj_type == OBJ_DELTA)
to_reuse = 1; /* check_object() decided it for us */
else if (obj_type != entry->in_pack_type)
to_reuse = 0; /* pack has delta which is unusable */
else if (entry->delta)
to_reuse = 0; /* we want to pack afresh */
else
to_reuse = 1; /* we have it in-pack undeltified,
* and we do not need to deltify it.
*/
if (! to_reuse) {
buf = read_sha1_file(entry->sha1, type, &size);
if (!buf)
die("unable to read %s", sha1_to_hex(entry->sha1));
if (size != entry->size)
die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
/*
* The object header is a byte of 'type' followed by zero or
* more bytes of length. For deltas, the 20 bytes of delta sha1
* follows that.
*/
obj_type = entry->type;
die("object %s size inconsistency (%lu vs %lu)",
sha1_to_hex(entry->sha1), size, entry->size);
if (entry->delta) {
buf = delta_against(buf, size, entry);
size = entry->delta_size;
obj_type = OBJ_DELTA;
}
/*
* The object header is a byte of 'type' followed by zero or
* more bytes of length. For deltas, the 20 bytes of delta
* sha1 follows that.
*/
hdrlen = encode_header(obj_type, size, header);
sha1write(f, header, hdrlen);
if (entry->delta) {
sha1write(f, entry->delta, 20);
hdrlen += 20;
}
datalen = sha1write_compressed(f, buf, size);
free(buf);
}
else {
struct packed_git *p = entry->in_pack;
use_packed_git(p);
datalen = find_packed_object_size(p, entry->in_pack_offset);
buf = p->pack_base + entry->in_pack_offset;
sha1write(f, buf, datalen);
unuse_packed_git(p);
hdrlen = 0; /* not really */
if (obj_type == OBJ_DELTA)
reused_delta++;
reused++;
}
if (obj_type == OBJ_DELTA)
written_delta++;
written++;
return hdrlen + datalen;
}
@ -132,7 +321,6 @@ static void write_pack_file(void)
int i;
struct sha1file *f;
unsigned long offset;
unsigned long mb;
struct pack_header hdr;
if (!base_name)
@ -148,8 +336,6 @@ static void write_pack_file(void)
offset = write_one(f, objects + i, offset);
sha1close(f, pack_file_sha1, 1);
mb = offset >> 20;
offset &= 0xfffff;
}
static void write_index_file(void)
@ -196,18 +382,20 @@ static int add_object_entry(unsigned char *sha1, unsigned int hash)
{
unsigned int idx = nr_objects;
struct object_entry *entry;
if (incremental || local) {
struct packed_git *p;
unsigned int found_offset = 0;
struct packed_git *found_pack = NULL;
for (p = packed_git; p; p = p->next) {
struct pack_entry e;
if (find_pack_entry_one(sha1, &e, p)) {
if (incremental)
return 0;
if (local && !p->pack_local)
return 0;
if (!found_pack) {
found_offset = e.offset;
found_pack = e.p;
}
}
}
@ -221,15 +409,85 @@ static int add_object_entry(unsigned char *sha1, unsigned int hash)
memset(entry, 0, sizeof(*entry));
memcpy(entry->sha1, sha1, 20);
entry->hash = hash;
if (found_pack) {
entry->in_pack = found_pack;
entry->in_pack_offset = found_offset;
}
nr_objects = idx+1;
return 1;
}
static int locate_object_entry_hash(unsigned char *sha1)
{
int i;
unsigned int ui;
memcpy(&ui, sha1, sizeof(unsigned int));
i = ui % object_ix_hashsz;
while (0 < object_ix[i]) {
if (!memcmp(sha1, objects[object_ix[i]-1].sha1, 20))
return i;
if (++i == object_ix_hashsz)
i = 0;
}
return -1 - i;
}
static struct object_entry *locate_object_entry(unsigned char *sha1)
{
int i = locate_object_entry_hash(sha1);
if (0 <= i)
return &objects[object_ix[i]-1];
return NULL;
}
static void check_object(struct object_entry *entry)
{
char type[20];
if (!sha1_object_info(entry->sha1, type, &entry->size)) {
if (entry->in_pack) {
unsigned char base[20];
unsigned long size;
struct object_entry *base_entry;
/* We want in_pack_type even if we do not reuse delta.
* There is no point not reusing non-delta representations.
*/
check_reuse_pack_delta(entry->in_pack,
entry->in_pack_offset,
base, &size,
&entry->in_pack_type);
/* Check if it is delta, and the base is also an object
* we are going to pack. If so we will reuse the existing
* delta.
*/
if (!no_reuse_delta &&
entry->in_pack_type == OBJ_DELTA &&
(base_entry = locate_object_entry(base))) {
/* Depth value does not matter - find_deltas()
* will never consider reused delta as the
* base object to deltify other objects
* against, in order to avoid circular deltas.
*/
/* uncompressed size of the delta data */
entry->size = entry->delta_size = size;
entry->delta = base_entry;
entry->type = OBJ_DELTA;
entry->delta_sibling = base_entry->delta_child;
base_entry->delta_child = entry;
return;
}
/* Otherwise we would do the usual */
}
if (sha1_object_info(entry->sha1, type, &entry->size))
die("unable to get type of object %s",
sha1_to_hex(entry->sha1));
if (!strcmp(type, "commit")) {
entry->type = OBJ_COMMIT;
} else if (!strcmp(type, "tree")) {
@ -242,18 +500,52 @@ static void check_object(struct object_entry *entry)
die("unable to pack object %s of type %s",
sha1_to_hex(entry->sha1), type);
}
else
die("unable to get type of object %s",
sha1_to_hex(entry->sha1));
static void hash_objects(void)
{
int i;
struct object_entry *oe;
object_ix_hashsz = nr_objects * 2;
object_ix = xcalloc(sizeof(int), object_ix_hashsz);
for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
int ix = locate_object_entry_hash(oe->sha1);
if (0 <= ix) {
error("the same object '%s' added twice",
sha1_to_hex(oe->sha1));
continue;
}
ix = -1 - ix;
object_ix[ix] = i + 1;
}
}
static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
{
struct object_entry *child = me->delta_child;
unsigned int m = n;
while (child) {
unsigned int c = check_delta_limit(child, n + 1);
if (m < c)
m = c;
child = child->delta_sibling;
}
return m;
}
static void get_object_details(void)
{
int i;
struct object_entry *entry = objects;
struct object_entry *entry;
for (i = 0; i < nr_objects; i++)
check_object(entry++);
hash_objects();
prepare_pack_ix();
for (i = 0, entry = objects; i < nr_objects; i++, entry++)
check_object(entry);
for (i = 0, entry = objects; i < nr_objects; i++, entry++)
if (!entry->delta && entry->delta_child)
entry->delta_limit =
check_delta_limit(entry, 1);
}
typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
@ -326,6 +618,16 @@ static int try_delta(struct unpacked *cur, struct unpacked *old, unsigned max_de
if (cur_entry->type != old_entry->type)
return -1;
/* If the current object is at edge, take the depth the objects
* that depend on the current object into account -- otherwise
* they would become too deep.
*/
if (cur_entry->delta_child) {
if (max_depth <= cur_entry->delta_limit)
return 0;
max_depth -= cur_entry->delta_limit;
}
size = cur_entry->size;
if (size < 50)
return -1;
@ -382,11 +684,19 @@ static void find_deltas(struct object_entry **list, int window, int depth)
eye_candy -= nr_objects / 20;
fputc('.', stderr);
}
if (entry->delta)
/* This happens if we decided to reuse existing
* delta from a pack. "!no_reuse_delta &&" is implied.
*/
continue;
free(n->data);
n->entry = entry;
n->data = read_sha1_file(entry->sha1, type, &size);
if (size != entry->size)
die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
j = window;
while (--j > 0) {
unsigned int other_idx = idx + j;
@ -411,10 +721,12 @@ static void find_deltas(struct object_entry **list, int window, int depth)
static void prepare_pack(int window, int depth)
{
get_object_details();
if (progress)
fprintf(stderr, "Packing %d objects", nr_objects);
get_object_details();
if (progress)
fputc('.', stderr);
sorted_by_type = create_sorted_list(type_size_sort);
if (window && depth)
find_deltas(sorted_by_type, window+1, depth);
@ -443,6 +755,7 @@ static int reuse_cached_pack(unsigned char *sha1, int pack_to_stdout)
}
}
if (progress)
fprintf(stderr, "Reusing %d objects pack %s\n", nr_objects,
sha1_to_hex(sha1));
@ -524,6 +837,10 @@ int main(int argc, char **argv)
progress = 0;
continue;
}
if (!strcmp("--no-reuse-delta", arg)) {
no_reuse_delta = 1;
continue;
}
if (!strcmp("--stdout", arg)) {
pack_to_stdout = 1;
continue;
@ -599,5 +916,8 @@ int main(int argc, char **argv)
puts(sha1_to_hex(object_list_sha1));
}
}
if (progress)
fprintf(stderr, "Total %d, written %d (delta %d), reused %d (delta %d)\n",
nr_objects, written, written_delta, reused, reused_delta);
return 0;
}

4
pack.h
View File

@ -29,5 +29,7 @@ struct pack_header {
};
extern int verify_pack(struct packed_git *, int);
extern int check_reuse_pack_delta(struct packed_git *, unsigned long,
unsigned char *, unsigned long *,
enum object_type *);
#endif

19
sha1_file.c
View File

@ -828,6 +828,25 @@ static unsigned long unpack_object_header(struct packed_git *p, unsigned long of
return offset;
}
int check_reuse_pack_delta(struct packed_git *p, unsigned long offset,
unsigned char *base, unsigned long *sizep,
enum object_type *kindp)
{
unsigned long ptr;
int status = -1;
use_packed_git(p);
ptr = offset;
ptr = unpack_object_header(p, ptr, kindp, sizep);
if (*kindp != OBJ_DELTA)
goto done;
memcpy(base, p->pack_base + ptr, 20);
status = 0;
done:
unuse_packed_git(p);
return status;
}
void packed_object_info_detail(struct pack_entry *e,
char *type,
unsigned long *size,