straighten the list of objects to deltify
[gitweb.git] / builtin-pack-objects.c
index ccb25f6a9c298bd977c5f55a84dd9a20a1e54e23..b1c64bec3ed0ae233241ea023208e9326d619350 100644 (file)
 #include "progress.h"
 
 static const char pack_usage[] = "\
-git-pack-objects [{ -q | --progress | --all-progress }] [--max-pack-size=N] \n\
-       [--local] [--incremental] [--window=N] [--depth=N] \n\
+git-pack-objects [{ -q | --progress | --all-progress }] \n\
+       [--max-pack-size=N] [--local] [--incremental] \n\
+       [--window=N] [--window-memory=N] [--depth=N] \n\
        [--no-reuse-delta] [--no-reuse-object] [--delta-base-offset] \n\
        [--non-empty] [--revs [--unpacked | --all]*] [--reflog] \n\
        [--stdout | base-name] [<ref-list | <object-list]";
 
 struct object_entry {
-       unsigned char sha1[20];
-       uint32_t crc32;         /* crc of raw pack data for this object */
-       off_t offset;           /* offset into the final pack file */
+       struct pack_idx_entry idx;
        unsigned long size;     /* uncompressed size */
-       unsigned int hash;      /* name hint hash */
-       unsigned int depth;     /* delta depth */
        struct packed_git *in_pack;     /* already in pack */
        off_t in_pack_offset;
        struct object_entry *delta;     /* delta base object */
@@ -38,6 +35,7 @@ struct object_entry {
                                             */
        void *delta_data;       /* cached delta (uncompressed) */
        unsigned long delta_size;       /* delta data size (uncompressed) */
+       unsigned int hash;      /* name hint hash */
        enum object_type type;
        enum object_type in_pack_type;  /* could be delta */
        unsigned char in_pack_header_size;
@@ -66,7 +64,6 @@ static int allow_ofs_delta;
 static const char *pack_tmp_name, *idx_tmp_name;
 static char tmpname[PATH_MAX];
 static const char *base_name;
-static unsigned char pack_file_sha1[20];
 static int progress = 1;
 static int window = 10;
 static uint32_t pack_size_limit;
@@ -81,6 +78,9 @@ static unsigned long delta_cache_size = 0;
 static unsigned long max_delta_cache_size = 0;
 static unsigned long cache_max_small_delta_size = 1000;
 
+static unsigned long window_memory_usage = 0;
+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.
@@ -246,15 +246,15 @@ static void *delta_against(void *buf, unsigned long size, struct object_entry *e
 {
        unsigned long othersize, delta_size;
        enum object_type type;
-       void *otherbuf = read_sha1_file(entry->delta->sha1, &type, &othersize);
+       void *otherbuf = read_sha1_file(entry->delta->idx.sha1, &type, &othersize);
        void *delta_buf;
 
        if (!otherbuf)
-               die("unable to read %s", sha1_to_hex(entry->delta->sha1));
+               die("unable to read %s", sha1_to_hex(entry->delta->idx.sha1));
         delta_buf = diff_delta(otherbuf, othersize,
                               buf, size, &delta_size, 0);
         if (!delta_buf || delta_size != entry->delta_size)
-               die("delta size changed");
+               die("delta size changed");
         free(buf);
         free(otherbuf);
        return delta_buf;
@@ -379,11 +379,11 @@ static unsigned long write_object(struct sha1file *f,
                                /* yes if unlimited packfile */
                                !pack_size_limit ? 1 :
                                /* no if base written to previous pack */
-                               entry->delta->offset == (off_t)-1 ? 0 :
+                               entry->delta->idx.offset == (off_t)-1 ? 0 :
                                /* otherwise double-check written to this
                                 * pack,  like we do below
                                 */
-                               entry->delta->offset ? 1 : 0;
+                               entry->delta->idx.offset ? 1 : 0;
 
        if (!pack_to_stdout)
                crc32_begin(f);
@@ -411,22 +411,22 @@ static unsigned long write_object(struct sha1file *f,
                unsigned long maxsize;
                void *out;
                if (!usable_delta) {
-                       buf = read_sha1_file(entry->sha1, &obj_type, &size);
+                       buf = read_sha1_file(entry->idx.sha1, &obj_type, &size);
                        if (!buf)
-                               die("unable to read %s", sha1_to_hex(entry->sha1));
+                               die("unable to read %s", sha1_to_hex(entry->idx.sha1));
                } else if (entry->delta_data) {
                        size = entry->delta_size;
                        buf = entry->delta_data;
                        entry->delta_data = NULL;
-                       obj_type = (allow_ofs_delta && entry->delta->offset) ?
+                       obj_type = (allow_ofs_delta && entry->delta->idx.offset) ?
                                OBJ_OFS_DELTA : OBJ_REF_DELTA;
                } else {
-                       buf = read_sha1_file(entry->sha1, &type, &size);
+                       buf = read_sha1_file(entry->idx.sha1, &type, &size);
                        if (!buf)
-                               die("unable to read %s", sha1_to_hex(entry->sha1));
+                               die("unable to read %s", sha1_to_hex(entry->idx.sha1));
                        buf = delta_against(buf, size, entry);
                        size = entry->delta_size;
-                       obj_type = (allow_ofs_delta && entry->delta->offset) ?
+                       obj_type = (allow_ofs_delta && entry->delta->idx.offset) ?
                                OBJ_OFS_DELTA : OBJ_REF_DELTA;
                }
                /* compress the data to store and put compressed length in datalen */
@@ -456,7 +456,7 @@ static unsigned long write_object(struct sha1file *f,
                         * encoding of the relative offset for the delta
                         * base from this object's position in the pack.
                         */
-                       off_t ofs = entry->offset - entry->delta->offset;
+                       off_t ofs = entry->idx.offset - entry->delta->idx.offset;
                        unsigned pos = sizeof(dheader) - 1;
                        dheader[pos] = ofs & 127;
                        while (ofs >>= 7)
@@ -480,7 +480,7 @@ static unsigned long write_object(struct sha1file *f,
                                return 0;
                        }
                        sha1write(f, header, hdrlen);
-                       sha1write(f, entry->delta->sha1, 20);
+                       sha1write(f, entry->delta->idx.sha1, 20);
                        hdrlen += 20;
                } else {
                        if (limit && hdrlen + datalen + 20 >= limit) {
@@ -501,7 +501,7 @@ static unsigned long write_object(struct sha1file *f,
                off_t offset;
 
                if (entry->delta) {
-                       obj_type = (allow_ofs_delta && entry->delta->offset) ?
+                       obj_type = (allow_ofs_delta && entry->delta->idx.offset) ?
                                OBJ_OFS_DELTA : OBJ_REF_DELTA;
                        reused_delta++;
                }
@@ -511,11 +511,11 @@ static unsigned long write_object(struct sha1file *f,
                datalen = revidx[1].offset - offset;
                if (!pack_to_stdout && p->index_version > 1 &&
                    check_pack_crc(p, &w_curs, offset, datalen, revidx->nr))
-                       die("bad packed object CRC for %s", sha1_to_hex(entry->sha1));
+                       die("bad packed object CRC for %s", sha1_to_hex(entry->idx.sha1));
                offset += entry->in_pack_header_size;
                datalen -= entry->in_pack_header_size;
                if (obj_type == OBJ_OFS_DELTA) {
-                       off_t ofs = entry->offset - entry->delta->offset;
+                       off_t ofs = entry->idx.offset - entry->delta->idx.offset;
                        unsigned pos = sizeof(dheader) - 1;
                        dheader[pos] = ofs & 127;
                        while (ofs >>= 7)
@@ -529,7 +529,7 @@ static unsigned long write_object(struct sha1file *f,
                        if (limit && hdrlen + 20 + datalen + 20 >= limit)
                                return 0;
                        sha1write(f, header, hdrlen);
-                       sha1write(f, entry->delta->sha1, 20);
+                       sha1write(f, entry->delta->idx.sha1, 20);
                        hdrlen += 20;
                } else {
                        if (limit && hdrlen + datalen + 20 >= limit)
@@ -539,7 +539,7 @@ static unsigned long write_object(struct sha1file *f,
 
                if (!pack_to_stdout && p->index_version == 1 &&
                    check_pack_inflate(p, &w_curs, offset, datalen, entry->size))
-                       die("corrupt packed object for %s", sha1_to_hex(entry->sha1));
+                       die("corrupt packed object for %s", sha1_to_hex(entry->idx.sha1));
                copy_pack_data(f, p, &w_curs, offset, datalen);
                unuse_pack(&w_curs);
                reused++;
@@ -548,7 +548,7 @@ static unsigned long write_object(struct sha1file *f,
                written_delta++;
        written++;
        if (!pack_to_stdout)
-               entry->crc32 = crc32_end(f);
+               entry->idx.crc32 = crc32_end(f);
        return hdrlen + datalen;
 }
 
@@ -559,7 +559,7 @@ static off_t write_one(struct sha1file *f,
        unsigned long size;
 
        /* offset is non zero if object is written already. */
-       if (e->offset || e->preferred_base)
+       if (e->idx.offset || e->preferred_base)
                return offset;
 
        /* if we are deltified, write out base object first. */
@@ -569,10 +569,10 @@ static off_t write_one(struct sha1file *f,
                        return 0;
        }
 
-       e->offset = offset;
+       e->idx.offset = offset;
        size = write_object(f, e, offset);
        if (!size) {
-               e->offset = 0;
+               e->idx.offset = 0;
                return 0;
        }
        written_list[nr_written++] = e;
@@ -586,11 +586,10 @@ static off_t write_one(struct sha1file *f,
 static int open_object_dir_tmp(const char *path)
 {
     snprintf(tmpname, sizeof(tmpname), "%s/%s", get_object_directory(), path);
-    return mkstemp(tmpname);
+    return xmkstemp(tmpname);
 }
 
-/* forward declarations for write_pack_file */
-static void write_index_file(off_t last_obj_offset, unsigned char *sha1);
+/* forward declaration for write_pack_file */
 static int adjust_perm(const char *path, mode_t mode);
 
 static void write_pack_file(void)
@@ -607,12 +606,12 @@ static void write_pack_file(void)
        written_list = xmalloc(nr_objects * sizeof(struct object_entry *));
 
        do {
+               unsigned char sha1[20];
+
                if (pack_to_stdout) {
                        f = sha1fd(1, "<stdout>");
                } else {
                        int fd = open_object_dir_tmp("tmp_pack_XXXXXX");
-                       if (fd < 0)
-                               die("unable to create %s: %s\n", tmpname, strerror(errno));
                        pack_tmp_name = xstrdup(tmpname);
                        f = sha1fd(fd, pack_tmp_name);
                }
@@ -638,23 +637,23 @@ static void write_pack_file(void)
                 * If so, rewrite it like in fast-import
                 */
                if (pack_to_stdout || nr_written == nr_remaining) {
-                       sha1close(f, pack_file_sha1, 1);
+                       sha1close(f, sha1, 1);
                } else {
-                       sha1close(f, pack_file_sha1, 0);
-                       fixup_pack_header_footer(f->fd, pack_file_sha1, pack_tmp_name, nr_written);
+                       sha1close(f, sha1, 0);
+                       fixup_pack_header_footer(f->fd, sha1, pack_tmp_name, nr_written);
                        close(f->fd);
                }
 
                if (!pack_to_stdout) {
-                       unsigned char object_list_sha1[20];
                        mode_t mode = umask(0);
 
                        umask(mode);
                        mode = 0444 & ~mode;
 
-                       write_index_file(last_obj_offset, object_list_sha1);
+                       idx_tmp_name = write_idx_file(NULL,
+                               (struct pack_idx_entry **) written_list, nr_written, sha1);
                        snprintf(tmpname, sizeof(tmpname), "%s-%s.pack",
-                                base_name, sha1_to_hex(object_list_sha1));
+                                base_name, sha1_to_hex(sha1));
                        if (adjust_perm(pack_tmp_name, mode))
                                die("unable to make temporary pack file readable: %s",
                                    strerror(errno));
@@ -662,19 +661,19 @@ static void write_pack_file(void)
                                die("unable to rename temporary pack file: %s",
                                    strerror(errno));
                        snprintf(tmpname, sizeof(tmpname), "%s-%s.idx",
-                                base_name, sha1_to_hex(object_list_sha1));
+                                base_name, sha1_to_hex(sha1));
                        if (adjust_perm(idx_tmp_name, mode))
                                die("unable to make temporary index file readable: %s",
                                    strerror(errno));
                        if (rename(idx_tmp_name, tmpname))
                                die("unable to rename temporary index file: %s",
                                    strerror(errno));
-                       puts(sha1_to_hex(object_list_sha1));
+                       puts(sha1_to_hex(sha1));
                }
 
                /* mark written objects as written to previous pack */
                for (j = 0; j < nr_written; j++) {
-                       written_list[j]->offset = (off_t)-1;
+                       written_list[j]->idx.offset = (off_t)-1;
                }
                nr_remaining -= nr_written;
        } while (nr_remaining && i < nr_objects);
@@ -692,129 +691,12 @@ static void write_pack_file(void)
         */
        for (j = 0; i < nr_objects; i++) {
                struct object_entry *e = objects + i;
-               j += !e->offset && !e->preferred_base;
+               j += !e->idx.offset && !e->preferred_base;
        }
        if (j)
                die("wrote %u objects as expected but %u unwritten", written, j);
 }
 
-static int sha1_sort(const void *_a, const void *_b)
-{
-       const struct object_entry *a = *(struct object_entry **)_a;
-       const struct object_entry *b = *(struct object_entry **)_b;
-       return hashcmp(a->sha1, b->sha1);
-}
-
-static uint32_t index_default_version = 1;
-static uint32_t index_off32_limit = 0x7fffffff;
-
-static void write_index_file(off_t last_obj_offset, unsigned char *sha1)
-{
-       struct sha1file *f;
-       struct object_entry **sorted_by_sha, **list, **last;
-       uint32_t array[256];
-       uint32_t i, index_version;
-       SHA_CTX ctx;
-
-       int fd = open_object_dir_tmp("tmp_idx_XXXXXX");
-       if (fd < 0)
-               die("unable to create %s: %s\n", tmpname, strerror(errno));
-       idx_tmp_name = xstrdup(tmpname);
-       f = sha1fd(fd, idx_tmp_name);
-
-       if (nr_written) {
-               sorted_by_sha = written_list;
-               qsort(sorted_by_sha, nr_written, sizeof(*sorted_by_sha), sha1_sort);
-               list = sorted_by_sha;
-               last = sorted_by_sha + nr_written;
-       } else
-               sorted_by_sha = list = last = NULL;
-
-       /* if last object's offset is >= 2^31 we should use index V2 */
-       index_version = (last_obj_offset >> 31) ? 2 : index_default_version;
-
-       /* index versions 2 and above need a header */
-       if (index_version >= 2) {
-               struct pack_idx_header hdr;
-               hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
-               hdr.idx_version = htonl(index_version);
-               sha1write(f, &hdr, sizeof(hdr));
-       }
-
-       /*
-        * Write the first-level table (the list is sorted,
-        * but we use a 256-entry lookup to be able to avoid
-        * having to do eight extra binary search iterations).
-        */
-       for (i = 0; i < 256; i++) {
-               struct object_entry **next = list;
-               while (next < last) {
-                       struct object_entry *entry = *next;
-                       if (entry->sha1[0] != i)
-                               break;
-                       next++;
-               }
-               array[i] = htonl(next - sorted_by_sha);
-               list = next;
-       }
-       sha1write(f, array, 256 * 4);
-
-       /* Compute the SHA1 hash of sorted object names. */
-       SHA1_Init(&ctx);
-
-       /* Write the actual SHA1 entries. */
-       list = sorted_by_sha;
-       for (i = 0; i < nr_written; i++) {
-               struct object_entry *entry = *list++;
-               if (index_version < 2) {
-                       uint32_t offset = htonl(entry->offset);
-                       sha1write(f, &offset, 4);
-               }
-               sha1write(f, entry->sha1, 20);
-               SHA1_Update(&ctx, entry->sha1, 20);
-       }
-
-       if (index_version >= 2) {
-               unsigned int nr_large_offset = 0;
-
-               /* write the crc32 table */
-               list = sorted_by_sha;
-               for (i = 0; i < nr_written; i++) {
-                       struct object_entry *entry = *list++;
-                       uint32_t crc32_val = htonl(entry->crc32);
-                       sha1write(f, &crc32_val, 4);
-               }
-
-               /* write the 32-bit offset table */
-               list = sorted_by_sha;
-               for (i = 0; i < nr_written; i++) {
-                       struct object_entry *entry = *list++;
-                       uint32_t offset = (entry->offset <= index_off32_limit) ?
-                               entry->offset : (0x80000000 | nr_large_offset++);
-                       offset = htonl(offset);
-                       sha1write(f, &offset, 4);
-               }
-
-               /* write the large offset table */
-               list = sorted_by_sha;
-               while (nr_large_offset) {
-                       struct object_entry *entry = *list++;
-                       uint64_t offset = entry->offset;
-                       if (offset > index_off32_limit) {
-                               uint32_t split[2];
-                               split[0]        = htonl(offset >> 32);
-                               split[1] = htonl(offset & 0xffffffff);
-                               sha1write(f, split, 8);
-                               nr_large_offset--;
-                       }
-               }
-       }
-
-       sha1write(f, pack_file_sha1, 20);
-       sha1close(f, NULL, 1);
-       SHA1_Final(sha1, &ctx);
-}
-
 static int locate_object_entry_hash(const unsigned char *sha1)
 {
        int i;
@@ -822,7 +704,7 @@ static int locate_object_entry_hash(const unsigned char *sha1)
        memcpy(&ui, sha1, sizeof(unsigned int));
        i = ui % object_ix_hashsz;
        while (0 < object_ix[i]) {
-               if (!hashcmp(sha1, objects[object_ix[i] - 1].sha1))
+               if (!hashcmp(sha1, objects[object_ix[i] - 1].idx.sha1))
                        return i;
                if (++i == object_ix_hashsz)
                        i = 0;
@@ -854,7 +736,7 @@ static void rehash_objects(void)
        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->sha1);
+               int ix = locate_object_entry_hash(oe->idx.sha1);
                if (0 <= ix)
                        continue;
                ix = -1 - ix;
@@ -948,7 +830,7 @@ static int add_object_entry(const unsigned char *sha1, enum object_type type,
 
        entry = objects + nr_objects++;
        memset(entry, 0, sizeof(*entry));
-       hashcpy(entry->sha1, sha1);
+       hashcpy(entry->idx.sha1, sha1);
        entry->hash = hash;
        if (type)
                entry->type = type;
@@ -1097,6 +979,8 @@ static void add_pbase_object(struct tree_desc *tree,
        int cmp;
 
        while (tree_entry(tree,&entry)) {
+               if (S_ISGITLINK(entry.mode))
+                       continue;
                cmp = tree_entry_len(entry.path, entry.sha1) != cmplen ? 1 :
                      memcmp(name, entry.path, cmplen);
                if (cmp > 0)
@@ -1268,13 +1152,13 @@ static void check_object(struct object_entry *entry)
                                ofs += 1;
                                if (!ofs || MSB(ofs, 7))
                                        die("delta base offset overflow in pack for %s",
-                                           sha1_to_hex(entry->sha1));
+                                           sha1_to_hex(entry->idx.sha1));
                                c = buf[used_0++];
                                ofs = (ofs << 7) + (c & 127);
                        }
                        if (ofs >= entry->in_pack_offset)
                                die("delta base offset out of bound for %s",
-                                   sha1_to_hex(entry->sha1));
+                                   sha1_to_hex(entry->idx.sha1));
                        ofs = entry->in_pack_offset - ofs;
                        if (!no_reuse_delta && !entry->preferred_base)
                                base_ref = find_packed_object_name(p, ofs);
@@ -1321,10 +1205,10 @@ static void check_object(struct object_entry *entry)
                unuse_pack(&w_curs);
        }
 
-       entry->type = sha1_object_info(entry->sha1, &entry->size);
+       entry->type = sha1_object_info(entry->idx.sha1, &entry->size);
        if (entry->type < 0)
                die("unable to get type of object %s",
-                   sha1_to_hex(entry->sha1));
+                   sha1_to_hex(entry->idx.sha1));
 }
 
 static int pack_offset_sort(const void *_a, const void *_b)
@@ -1334,7 +1218,7 @@ static int pack_offset_sort(const void *_a, const void *_b)
 
        /* avoid filesystem trashing with loose objects */
        if (!a->in_pack && !b->in_pack)
-               return hashcmp(a->sha1, b->sha1);
+               return hashcmp(a->idx.sha1, b->idx.sha1);
 
        if (a->in_pack < b->in_pack)
                return -1;
@@ -1388,11 +1272,11 @@ struct unpacked {
        struct object_entry *entry;
        void *data;
        struct delta_index *index;
+       unsigned depth;
 };
 
-static int delta_cacheable(struct unpacked *trg, struct unpacked *src,
-                           unsigned long src_size, unsigned long trg_size,
-                           unsigned long delta_size)
+static int delta_cacheable(unsigned long src_size, unsigned long trg_size,
+                          unsigned long delta_size)
 {
        if (max_delta_cache_size && delta_cache_size + delta_size > max_delta_cache_size)
                return 0;
@@ -1421,6 +1305,7 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
        struct object_entry *trg_entry = trg->entry;
        struct object_entry *src_entry = src->entry;
        unsigned long trg_size, src_size, delta_size, sizediff, max_size, sz;
+       unsigned ref_depth;
        enum object_type type;
        void *delta_buf;
 
@@ -1428,12 +1313,6 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
        if (trg_entry->type != src_entry->type)
                return -1;
 
-       /* We do not compute delta to *create* objects we are not
-        * going to pack.
-        */
-       if (trg_entry->preferred_base)
-               return -1;
-
        /*
         * We do not bother to try a delta that we discarded
         * on an earlier try, but only when reusing delta data.
@@ -1445,34 +1324,49 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
                return 0;
 
        /* Let's not bust the allowed depth. */
-       if (src_entry->depth >= max_depth)
+       if (src->depth >= max_depth)
                return 0;
 
        /* Now some size filtering heuristics. */
        trg_size = trg_entry->size;
-       max_size = trg_size/2 - 20;
-       max_size = max_size * (max_depth - src_entry->depth) / max_depth;
+       if (!trg_entry->delta) {
+               max_size = trg_size/2 - 20;
+               ref_depth = 1;
+       } else {
+               max_size = trg_entry->delta_size;
+               ref_depth = trg->depth;
+       }
+       max_size = max_size * (max_depth - src->depth) /
+                                               (max_depth - ref_depth + 1);
        if (max_size == 0)
                return 0;
-       if (trg_entry->delta && trg_entry->delta_size <= max_size)
-               max_size = trg_entry->delta_size-1;
        src_size = src_entry->size;
        sizediff = src_size < trg_size ? trg_size - src_size : 0;
        if (sizediff >= max_size)
                return 0;
+       if (trg_size < src_size / 32)
+               return 0;
 
        /* Load data if not already done */
        if (!trg->data) {
-               trg->data = read_sha1_file(trg_entry->sha1, &type, &sz);
+               trg->data = read_sha1_file(trg_entry->idx.sha1, &type, &sz);
+               if (!trg->data)
+                       die("object %s cannot be read",
+                           sha1_to_hex(trg_entry->idx.sha1));
                if (sz != trg_size)
                        die("object %s inconsistent object length (%lu vs %lu)",
-                           sha1_to_hex(trg_entry->sha1), sz, trg_size);
+                           sha1_to_hex(trg_entry->idx.sha1), sz, trg_size);
+               window_memory_usage += sz;
        }
        if (!src->data) {
-               src->data = read_sha1_file(src_entry->sha1, &type, &sz);
+               src->data = read_sha1_file(src_entry->idx.sha1, &type, &sz);
+               if (!src->data)
+                       die("object %s cannot be read",
+                           sha1_to_hex(src_entry->idx.sha1));
                if (sz != src_size)
                        die("object %s inconsistent object length (%lu vs %lu)",
-                           sha1_to_hex(src_entry->sha1), sz, src_size);
+                           sha1_to_hex(src_entry->idx.sha1), sz, src_size);
+               window_memory_usage += sz;
        }
        if (!src->index) {
                src->index = create_delta_index(src->data, src_size);
@@ -1482,22 +1376,33 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
                                warning("suboptimal pack - out of memory");
                        return 0;
                }
+               window_memory_usage += sizeof_delta_index(src->index);
        }
 
        delta_buf = create_delta(src->index, trg->data, trg_size, &delta_size, max_size);
        if (!delta_buf)
                return 0;
 
+       if (trg_entry->delta) {
+               /* Prefer only shallower same-sized deltas. */
+               if (delta_size == trg_entry->delta_size &&
+                   src->depth + 1 >= trg->depth) {
+                       free(delta_buf);
+                       return 0;
+               }
+       }
+
+       trg_entry->delta = src_entry;
+       trg_entry->delta_size = delta_size;
+       trg->depth = src->depth + 1;
+
        if (trg_entry->delta_data) {
                delta_cache_size -= trg_entry->delta_size;
                free(trg_entry->delta_data);
+               trg_entry->delta_data = NULL;
        }
-       trg_entry->delta_data = 0;
-       trg_entry->delta = src_entry;
-       trg_entry->delta_size = delta_size;
-       trg_entry->depth = src_entry->depth + 1;
 
-       if (delta_cacheable(src, trg, src_size, trg_size, delta_size)) {
+       if (delta_cacheable(src_size, trg_size, delta_size)) {
                trg_entry->delta_data = xrealloc(delta_buf, delta_size);
                delta_cache_size += trg_entry->delta_size;
        } else
@@ -1518,48 +1423,57 @@ static unsigned int check_delta_limit(struct object_entry *me, unsigned int n)
        return m;
 }
 
-static void find_deltas(struct object_entry **list, int window, int depth)
+static void free_unpacked(struct unpacked *n)
 {
-       uint32_t i = nr_objects, idx = 0, processed = 0;
+       window_memory_usage -= sizeof_delta_index(n->index);
+       free_delta_index(n->index);
+       n->index = NULL;
+       if (n->data) {
+               free(n->data);
+               n->data = NULL;
+               window_memory_usage -= n->entry->size;
+       }
+       n->entry = NULL;
+       n->depth = 0;
+}
+
+static void find_deltas(struct object_entry **list, unsigned list_size,
+                       unsigned nr_deltas, int window, int depth)
+{
+       uint32_t i = list_size, idx = 0, count = 0, processed = 0;
        unsigned int array_size = window * sizeof(struct unpacked);
        struct unpacked *array;
        int max_depth;
 
-       if (!nr_objects)
-               return;
        array = xmalloc(array_size);
        memset(array, 0, array_size);
        if (progress)
-               start_progress(&progress_state, "Deltifying %u objects...", "", nr_result);
+               start_progress(&progress_state, "Deltifying %u objects...", "", nr_deltas);
 
        do {
                struct object_entry *entry = list[--i];
                struct unpacked *n = array + idx;
-               int j;
-
-               if (!entry->preferred_base)
-                       processed++;
-
-               if (progress)
-                       display_progress(&progress_state, processed);
+               int j, best_base = -1;
 
-               if (entry->delta)
-                       /* This happens if we decided to reuse existing
-                        * delta from a pack.  "!no_reuse_delta &&" is implied.
-                        */
-                       continue;
+               free_unpacked(n);
+               n->entry = entry;
 
-               if (entry->size < 50)
-                       continue;
+               while (window_memory_limit &&
+                      window_memory_usage > window_memory_limit &&
+                      count > 1) {
+                       uint32_t tail = (idx + window - count) % window;
+                       free_unpacked(array + tail);
+                       count--;
+               }
 
-               if (entry->no_try_delta)
-                       continue;
+               /* We do not compute delta to *create* objects we are not
+                * going to pack.
+                */
+               if (entry->preferred_base)
+                       goto next;
 
-               free_delta_index(n->index);
-               n->index = NULL;
-               free(n->data);
-               n->data = NULL;
-               n->entry = entry;
+               if (progress)
+                       display_progress(&progress_state, ++processed);
 
                /*
                 * If the current object is at pack edge, take the depth the
@@ -1575,6 +1489,7 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 
                j = window;
                while (--j > 0) {
+                       int ret;
                        uint32_t other_idx = idx + j;
                        struct unpacked *m;
                        if (other_idx >= window)
@@ -1582,19 +1497,41 @@ static void find_deltas(struct object_entry **list, int window, int depth)
                        m = array + other_idx;
                        if (!m->entry)
                                break;
-                       if (try_delta(n, m, max_depth) < 0)
+                       ret = try_delta(n, m, max_depth);
+                       if (ret < 0)
                                break;
+                       else if (ret > 0)
+                               best_base = other_idx;
                }
 
                /* if we made n a delta, and if n is already at max
                 * depth, leaving it in the window is pointless.  we
                 * should evict it first.
                 */
-               if (entry->delta && depth <= entry->depth)
+               if (entry->delta && depth <= n->depth)
                        continue;
 
+               /*
+                * Move the best delta base up in the window, after the
+                * currently deltified object, to keep it longer.  It will
+                * be the first base object to be attempted next.
+                */
+               if (entry->delta) {
+                       struct unpacked swap = array[best_base];
+                       int dist = (window + idx - best_base) % window;
+                       int dst = best_base;
+                       while (dist--) {
+                               int src = (dst + 1) % window;
+                               array[dst] = array[src];
+                               dst = src;
+                       }
+                       array[dst] = swap;
+               }
+
                next:
                idx++;
+               if (count + 1 < window)
+                       count++;
                if (idx >= window)
                        idx = 0;
        } while (i > 0);
@@ -1612,18 +1549,41 @@ static void find_deltas(struct object_entry **list, int window, int depth)
 static void prepare_pack(int window, int depth)
 {
        struct object_entry **delta_list;
-       uint32_t i;
+       uint32_t i, n, nr_deltas;
 
        get_object_details();
 
-       if (!window || !depth)
+       if (!nr_objects || !window || !depth)
                return;
 
        delta_list = xmalloc(nr_objects * sizeof(*delta_list));
-       for (i = 0; i < nr_objects; i++)
-               delta_list[i] = objects + i;
-       qsort(delta_list, nr_objects, sizeof(*delta_list), type_size_sort);
-       find_deltas(delta_list, window+1, depth);
+       nr_deltas = n = 0;
+
+       for (i = 0; i < nr_objects; i++) {
+               struct object_entry *entry = objects + i;
+
+               if (entry->delta)
+                       /* This happens if we decided to reuse existing
+                        * delta from a pack.  "!no_reuse_delta &&" is implied.
+                        */
+                       continue;
+
+               if (entry->size < 50)
+                       continue;
+
+               if (entry->no_try_delta)
+                       continue;
+
+               if (!entry->preferred_base)
+                       nr_deltas++;
+
+               delta_list[n++] = entry;
+       }
+
+       if (nr_deltas) {
+               qsort(delta_list, n, sizeof(*delta_list), type_size_sort);
+               find_deltas(delta_list, n, nr_deltas, window+1, depth);
+       }
        free(delta_list);
 }
 
@@ -1633,7 +1593,11 @@ static int git_pack_config(const char *k, const char *v)
                window = git_config_int(k, v);
                return 0;
        }
-       if(!strcmp(k, "pack.depth")) {
+       if (!strcmp(k, "pack.windowmemory")) {
+               window_memory_limit = git_config_ulong(k, v);
+               return 0;
+       }
+       if (!strcmp(k, "pack.depth")) {
                depth = git_config_int(k, v);
                return 0;
        }
@@ -1809,6 +1773,11 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
                                usage(pack_usage);
                        continue;
                }
+               if (!prefixcmp(arg, "--window-memory=")) {
+                       if (!git_parse_ulong(arg+16, &window_memory_limit))
+                               usage(pack_usage);
+                       continue;
+               }
                if (!prefixcmp(arg, "--depth=")) {
                        char *end;
                        depth = strtoul(arg+8, &end, 0);
@@ -1869,12 +1838,12 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
                }
                if (!prefixcmp(arg, "--index-version=")) {
                        char *c;
-                       index_default_version = strtoul(arg + 16, &c, 10);
-                       if (index_default_version > 2)
+                       pack_idx_default_version = strtoul(arg + 16, &c, 10);
+                       if (pack_idx_default_version > 2)
                                die("bad %s", arg);
                        if (*c == ',')
-                               index_off32_limit = strtoul(c+1, &c, 0);
-                       if (*c || index_off32_limit & 0x80000000)
+                               pack_idx_off32_limit = strtoul(c+1, &c, 0);
+                       if (*c || pack_idx_off32_limit & 0x80000000)
                                die("bad %s", arg);
                        continue;
                }