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pack-objects: refactor the packing list
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The hash table that stores the packing list for a given `pack-objects`
run was tightly coupled to the pack-objects code.

In this commit, we refactor the hash table and the underlying storage
array into a `packing_data` struct. The functionality for accessing and
adding entries to the packing list is hence accessible from other parts
of Git besides the `pack-objects` builtin.

This refactoring is a requirement for further patches in this series
that will require accessing the commit packing list from outside of
`pack-objects`.

The hash table implementation has been minimally altered: we now
use table sizes which are always a power of two, to ensure a uniform
index distribution in the array.

Signed-off-by: Vicent Marti <tanoku@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Vicent Marti authored and Junio C Hamano committed Oct 24, 2013
1 parent 92e5c77 commit 2834bc2
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Showing 4 changed files with 200 additions and 135 deletions.
2 changes: 2 additions & 0 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -694,6 +694,7 @@ LIB_H += notes-merge.h
LIB_H += notes-utils.h
LIB_H += notes.h
LIB_H += object.h
LIB_H += pack-objects.h
LIB_H += pack-revindex.h
LIB_H += pack.h
LIB_H += parse-options.h
Expand Down Expand Up @@ -831,6 +832,7 @@ LIB_OBJS += notes-merge.o
LIB_OBJS += notes-utils.o
LIB_OBJS += object.o
LIB_OBJS += pack-check.o
LIB_OBJS += pack-objects.o
LIB_OBJS += pack-revindex.o
LIB_OBJS += pack-write.o
LIB_OBJS += pager.o
Expand Down
175 changes: 40 additions & 135 deletions builtin/pack-objects.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include "diff.h"
#include "revision.h"
#include "list-objects.h"
#include "pack-objects.h"
#include "progress.h"
#include "refs.h"
#include "streaming.h"
Expand All @@ -25,42 +26,15 @@ static const char *pack_usage[] = {
NULL
};

struct object_entry {
struct pack_idx_entry idx;
unsigned long size; /* uncompressed size */
struct packed_git *in_pack; /* already in pack */
off_t in_pack_offset;
struct object_entry *delta; /* delta base object */
struct object_entry *delta_child; /* deltified objects who bases me */
struct object_entry *delta_sibling; /* other deltified objects who
* uses the same base as me
*/
void *delta_data; /* cached delta (uncompressed) */
unsigned long delta_size; /* delta data size (uncompressed) */
unsigned long z_delta_size; /* delta data size (compressed) */
enum object_type type;
enum object_type in_pack_type; /* could be delta */
uint32_t hash; /* name hint hash */
unsigned char in_pack_header_size;
unsigned preferred_base:1; /*
* we do not pack this, but is available
* to be used as the base object to delta
* objects against.
*/
unsigned no_try_delta:1;
unsigned tagged:1; /* near the very tip of refs */
unsigned filled:1; /* assigned write-order */
};

/*
* Objects we are going to pack are collected 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.
* Objects we are going to pack are collected in the `to_pack` structure.
* It contains an array (dynamically expanded) of the object data, and a map
* that can resolve SHA1s to their position in the array.
*/
static struct object_entry *objects;
static struct packing_data to_pack;

static struct pack_idx_entry **written_list;
static uint32_t nr_objects, nr_alloc, nr_result, nr_written;
static uint32_t nr_result, nr_written;

static int non_empty;
static int reuse_delta = 1, reuse_object = 1;
Expand Down Expand Up @@ -89,22 +63,12 @@ static unsigned long cache_max_small_delta_size = 1000;

static unsigned long window_memory_limit = 0;

/*
* The object names in objects array are hashed with this hashtable,
* to help looking up the entry by object name.
* This hashtable is built after all the objects are seen.
*/
static int *object_ix;
static int object_ix_hashsz;
static struct object_entry *locate_object_entry(const unsigned char *sha1);

/*
* stats
*/
static uint32_t written, written_delta;
static uint32_t reused, reused_delta;


static void *get_delta(struct object_entry *entry)
{
unsigned long size, base_size, delta_size;
Expand Down Expand Up @@ -553,12 +517,12 @@ static int mark_tagged(const char *path, const unsigned char *sha1, int flag,
void *cb_data)
{
unsigned char peeled[20];
struct object_entry *entry = locate_object_entry(sha1);
struct object_entry *entry = packlist_find(&to_pack, sha1, NULL);

if (entry)
entry->tagged = 1;
if (!peel_ref(path, peeled)) {
entry = locate_object_entry(peeled);
entry = packlist_find(&to_pack, peeled, NULL);
if (entry)
entry->tagged = 1;
}
Expand Down Expand Up @@ -633,9 +597,10 @@ static struct object_entry **compute_write_order(void)
{
unsigned int i, wo_end, last_untagged;

struct object_entry **wo = xmalloc(nr_objects * sizeof(*wo));
struct object_entry **wo = xmalloc(to_pack.nr_objects * sizeof(*wo));
struct object_entry *objects = to_pack.objects;

for (i = 0; i < nr_objects; i++) {
for (i = 0; i < to_pack.nr_objects; i++) {
objects[i].tagged = 0;
objects[i].filled = 0;
objects[i].delta_child = NULL;
Expand All @@ -647,7 +612,7 @@ static struct object_entry **compute_write_order(void)
* Make sure delta_sibling is sorted in the original
* recency order.
*/
for (i = nr_objects; i > 0;) {
for (i = to_pack.nr_objects; i > 0;) {
struct object_entry *e = &objects[--i];
if (!e->delta)
continue;
Expand All @@ -665,7 +630,7 @@ static struct object_entry **compute_write_order(void)
* Give the objects in the original recency order until
* we see a tagged tip.
*/
for (i = wo_end = 0; i < nr_objects; i++) {
for (i = wo_end = 0; i < to_pack.nr_objects; i++) {
if (objects[i].tagged)
break;
add_to_write_order(wo, &wo_end, &objects[i]);
Expand All @@ -675,15 +640,15 @@ static struct object_entry **compute_write_order(void)
/*
* Then fill all the tagged tips.
*/
for (; i < nr_objects; i++) {
for (; i < to_pack.nr_objects; i++) {
if (objects[i].tagged)
add_to_write_order(wo, &wo_end, &objects[i]);
}

/*
* And then all remaining commits and tags.
*/
for (i = last_untagged; i < nr_objects; i++) {
for (i = last_untagged; i < to_pack.nr_objects; i++) {
if (objects[i].type != OBJ_COMMIT &&
objects[i].type != OBJ_TAG)
continue;
Expand All @@ -693,7 +658,7 @@ static struct object_entry **compute_write_order(void)
/*
* And then all the trees.
*/
for (i = last_untagged; i < nr_objects; i++) {
for (i = last_untagged; i < to_pack.nr_objects; i++) {
if (objects[i].type != OBJ_TREE)
continue;
add_to_write_order(wo, &wo_end, &objects[i]);
Expand All @@ -702,13 +667,13 @@ static struct object_entry **compute_write_order(void)
/*
* Finally all the rest in really tight order
*/
for (i = last_untagged; i < nr_objects; i++) {
for (i = last_untagged; i < to_pack.nr_objects; i++) {
if (!objects[i].filled)
add_family_to_write_order(wo, &wo_end, &objects[i]);
}

if (wo_end != nr_objects)
die("ordered %u objects, expected %"PRIu32, wo_end, nr_objects);
if (wo_end != to_pack.nr_objects)
die("ordered %u objects, expected %"PRIu32, wo_end, to_pack.nr_objects);

return wo;
}
Expand All @@ -724,7 +689,7 @@ static void write_pack_file(void)

if (progress > pack_to_stdout)
progress_state = start_progress("Writing objects", nr_result);
written_list = xmalloc(nr_objects * sizeof(*written_list));
written_list = xmalloc(to_pack.nr_objects * sizeof(*written_list));
write_order = compute_write_order();

do {
Expand All @@ -740,7 +705,7 @@ static void write_pack_file(void)
if (!offset)
die_errno("unable to write pack header");
nr_written = 0;
for (; i < nr_objects; i++) {
for (; i < to_pack.nr_objects; i++) {
struct object_entry *e = write_order[i];
if (write_one(f, e, &offset) == WRITE_ONE_BREAK)
break;
Expand Down Expand Up @@ -803,7 +768,7 @@ static void write_pack_file(void)
written_list[j]->offset = (off_t)-1;
}
nr_remaining -= nr_written;
} while (nr_remaining && i < nr_objects);
} while (nr_remaining && i < to_pack.nr_objects);

free(written_list);
free(write_order);
Expand All @@ -813,53 +778,6 @@ static void write_pack_file(void)
written, nr_result);
}

static int locate_object_entry_hash(const 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 (!hashcmp(sha1, objects[object_ix[i] - 1].idx.sha1))
return i;
if (++i == object_ix_hashsz)
i = 0;
}
return -1 - i;
}

static struct object_entry *locate_object_entry(const unsigned char *sha1)
{
int i;

if (!object_ix_hashsz)
return NULL;

i = locate_object_entry_hash(sha1);
if (0 <= i)
return &objects[object_ix[i]-1];
return NULL;
}

static void rehash_objects(void)
{
uint32_t i;
struct object_entry *oe;

object_ix_hashsz = nr_objects * 3;
if (object_ix_hashsz < 1024)
object_ix_hashsz = 1024;
object_ix = xrealloc(object_ix, sizeof(int) * object_ix_hashsz);
memset(object_ix, 0, sizeof(int) * object_ix_hashsz);
for (i = 0, oe = objects; i < nr_objects; i++, oe++) {
int ix = locate_object_entry_hash(oe->idx.sha1);
if (0 <= ix)
continue;
ix = -1 - ix;
object_ix[ix] = i + 1;
}
}

static uint32_t name_hash(const char *name)
{
uint32_t c, hash = 0;
Expand Down Expand Up @@ -908,13 +826,12 @@ static int add_object_entry(const unsigned char *sha1, enum object_type type,
struct object_entry *entry;
struct packed_git *p, *found_pack = NULL;
off_t found_offset = 0;
int ix;
uint32_t hash = name_hash(name);
uint32_t index_pos;

ix = nr_objects ? locate_object_entry_hash(sha1) : -1;
if (ix >= 0) {
entry = packlist_find(&to_pack, sha1, &index_pos);
if (entry) {
if (exclude) {
entry = objects + object_ix[ix] - 1;
if (!entry->preferred_base)
nr_result--;
entry->preferred_base = 1;
Expand Down Expand Up @@ -947,14 +864,7 @@ static int add_object_entry(const unsigned char *sha1, enum object_type type,
}
}

if (nr_objects >= nr_alloc) {
nr_alloc = (nr_alloc + 1024) * 3 / 2;
objects = xrealloc(objects, nr_alloc * sizeof(*entry));
}

entry = objects + nr_objects++;
memset(entry, 0, sizeof(*entry));
hashcpy(entry->idx.sha1, sha1);
entry = packlist_alloc(&to_pack, sha1, index_pos);
entry->hash = hash;
if (type)
entry->type = type;
Expand All @@ -967,12 +877,7 @@ static int add_object_entry(const unsigned char *sha1, enum object_type type,
entry->in_pack_offset = found_offset;
}

if (object_ix_hashsz * 3 <= nr_objects * 4)
rehash_objects();
else
object_ix[-1 - ix] = nr_objects;

display_progress(progress_state, nr_objects);
display_progress(progress_state, to_pack.nr_objects);

if (name && no_try_delta(name))
entry->no_try_delta = 1;
Expand Down Expand Up @@ -1329,7 +1234,7 @@ static void check_object(struct object_entry *entry)
break;
}

if (base_ref && (base_entry = locate_object_entry(base_ref))) {
if (base_ref && (base_entry = packlist_find(&to_pack, base_ref, NULL))) {
/*
* If base_ref was set above that means we wish to
* reuse delta data, and we even found that base
Expand Down Expand Up @@ -1403,12 +1308,12 @@ static void get_object_details(void)
uint32_t i;
struct object_entry **sorted_by_offset;

sorted_by_offset = xcalloc(nr_objects, sizeof(struct object_entry *));
for (i = 0; i < nr_objects; i++)
sorted_by_offset[i] = objects + i;
qsort(sorted_by_offset, nr_objects, sizeof(*sorted_by_offset), pack_offset_sort);
sorted_by_offset = xcalloc(to_pack.nr_objects, sizeof(struct object_entry *));
for (i = 0; i < to_pack.nr_objects; i++)
sorted_by_offset[i] = to_pack.objects + i;
qsort(sorted_by_offset, to_pack.nr_objects, sizeof(*sorted_by_offset), pack_offset_sort);

for (i = 0; i < nr_objects; i++) {
for (i = 0; i < to_pack.nr_objects; i++) {
struct object_entry *entry = sorted_by_offset[i];
check_object(entry);
if (big_file_threshold < entry->size)
Expand Down Expand Up @@ -2034,7 +1939,7 @@ static int add_ref_tag(const char *path, const unsigned char *sha1, int flag, vo

if (!prefixcmp(path, "refs/tags/") && /* is a tag? */
!peel_ref(path, peeled) && /* peelable? */
locate_object_entry(peeled)) /* object packed? */
packlist_find(&to_pack, peeled, NULL)) /* object packed? */
add_object_entry(sha1, OBJ_TAG, NULL, 0);
return 0;
}
Expand All @@ -2057,14 +1962,14 @@ static void prepare_pack(int window, int depth)
if (!pack_to_stdout)
do_check_packed_object_crc = 1;

if (!nr_objects || !window || !depth)
if (!to_pack.nr_objects || !window || !depth)
return;

delta_list = xmalloc(nr_objects * sizeof(*delta_list));
delta_list = xmalloc(to_pack.nr_objects * sizeof(*delta_list));
nr_deltas = n = 0;

for (i = 0; i < nr_objects; i++) {
struct object_entry *entry = objects + i;
for (i = 0; i < to_pack.nr_objects; i++) {
struct object_entry *entry = to_pack.objects + i;

if (entry->delta)
/* This happens if we decided to reuse existing
Expand Down Expand Up @@ -2342,7 +2247,7 @@ static void loosen_unused_packed_objects(struct rev_info *revs)

for (i = 0; i < p->num_objects; i++) {
sha1 = nth_packed_object_sha1(p, i);
if (!locate_object_entry(sha1) &&
if (!packlist_find(&to_pack, sha1, NULL) &&
!has_sha1_pack_kept_or_nonlocal(sha1))
if (force_object_loose(sha1, p->mtime))
die("unable to force loose object");
Expand Down
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