From c6458e60ed0f3e26a1df88bf5a3da8b091b0ce15 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Nguy=E1=BB=85n=20Th=C3=A1i=20Ng=E1=BB=8Dc=20Duy?= Date: Sat, 18 Apr 2015 17:47:05 +0700 Subject: [PATCH] index-pack: kill union delta_base to save memory MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Once we know the number of objects in the input pack, we allocate an array of nr_objects of struct delta_entry. On x86-64, this struct is 32 bytes long. The union delta_base, which is part of struct delta_entry, provides enough space to store either ofs-delta (8 bytes) or ref-delta (20 bytes). Because ofs-delta encoding is more efficient space-wise and more performant at runtime than ref-delta encoding, Git packers try to use ofs-delta whenever possible, and it is expected that objects encoded as ref-delta are minority. In the best clone case where no ref-delta object is present, we waste (20-8) * nr_objects bytes because of this union. That's about 38MB out of 100MB for deltas[] with 3.4M objects, or 38%. deltas[] would be around 62MB without the waste. This patch attempts to eliminate that. deltas[] array is split into two: one for ofs-delta and one for ref-delta. Many functions are also duplicated because of this split. With this patch, ofs_deltas[] array takes 51MB. ref_deltas[] should remain unallocated in clone case (0 bytes). This array grows as we see ref-delta. We save about half in this case, or 25% of total bookkeeping. The saving is more than the calculation above because some padding in the old delta_entry struct is removed. ofs_delta_entry is 16 bytes, including the 4 bytes padding. That's 13MB for padding, but packing the struct could break platforms that do not support unaligned access. If someone on 32-bit is really low on memory and only deals with packs smaller than 2G, using 32-bit off_t would eliminate the padding and save 27MB on top. A note about ofs_deltas allocation. We could use ref_deltas memory allocation strategy for ofs_deltas. But that probably just adds more overhead on top. ofs-deltas are generally the majority (1/2 to 2/3) in any pack. Incremental realloc may lead to too many memcpy. And if we preallocate, say 1/2 or 2/3 of nr_objects initially, the growth rate of ALLOC_GROW() could make this array larger than nr_objects, wasting more memory. Brought-up-by: Matthew Sporleder Signed-off-by: Nguyễn Thái Ngọc Duy Signed-off-by: Junio C Hamano --- builtin/index-pack.c | 256 ++++++++++++++++++++++++++----------------- 1 file changed, 158 insertions(+), 98 deletions(-) diff --git a/builtin/index-pack.c b/builtin/index-pack.c index 9d854fb751..3ed53e3c9b 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -28,11 +28,6 @@ struct object_stat { int base_object_no; }; -union delta_base { - unsigned char sha1[20]; - off_t offset; -}; - struct base_data { struct base_data *base; struct base_data *child; @@ -52,26 +47,28 @@ struct thread_local { int pack_fd; }; -/* - * Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want - * to memcmp() only the first 20 bytes. - */ -#define UNION_BASE_SZ 20 - #define FLAG_LINK (1u<<20) #define FLAG_CHECKED (1u<<21) -struct delta_entry { - union delta_base base; +struct ofs_delta_entry { + off_t offset; + int obj_no; +}; + +struct ref_delta_entry { + unsigned char sha1[20]; int obj_no; }; static struct object_entry *objects; static struct object_stat *obj_stat; -static struct delta_entry *deltas; +static struct ofs_delta_entry *ofs_deltas; +static struct ref_delta_entry *ref_deltas; static struct thread_local nothread_data; static int nr_objects; -static int nr_deltas; +static int nr_ofs_deltas; +static int nr_ref_deltas; +static int ref_deltas_alloc; static int nr_resolved_deltas; static int nr_threads; @@ -480,7 +477,8 @@ static void *unpack_entry_data(unsigned long offset, unsigned long size, } static void *unpack_raw_entry(struct object_entry *obj, - union delta_base *delta_base, + off_t *ofs_offset, + unsigned char *ref_sha1, unsigned char *sha1) { unsigned char *p; @@ -509,11 +507,10 @@ static void *unpack_raw_entry(struct object_entry *obj, switch (obj->type) { case OBJ_REF_DELTA: - hashcpy(delta_base->sha1, fill(20)); + hashcpy(ref_sha1, fill(20)); use(20); break; case OBJ_OFS_DELTA: - memset(delta_base, 0, sizeof(*delta_base)); p = fill(1); c = *p; use(1); @@ -527,8 +524,8 @@ static void *unpack_raw_entry(struct object_entry *obj, use(1); base_offset = (base_offset << 7) + (c & 127); } - delta_base->offset = obj->idx.offset - base_offset; - if (delta_base->offset <= 0 || delta_base->offset >= obj->idx.offset) + *ofs_offset = obj->idx.offset - base_offset; + if (*ofs_offset <= 0 || *ofs_offset >= obj->idx.offset) bad_object(obj->idx.offset, _("delta base offset is out of bound")); break; case OBJ_COMMIT: @@ -612,55 +609,108 @@ static void *get_data_from_pack(struct object_entry *obj) return unpack_data(obj, NULL, NULL); } -static int compare_delta_bases(const union delta_base *base1, - const union delta_base *base2, - enum object_type type1, - enum object_type type2) +static int compare_ofs_delta_bases(off_t offset1, off_t offset2, + enum object_type type1, + enum object_type type2) { int cmp = type1 - type2; if (cmp) return cmp; - return memcmp(base1, base2, UNION_BASE_SZ); + return offset1 - offset2; } -static int find_delta(const union delta_base *base, enum object_type type) +static int find_ofs_delta(const off_t offset, enum object_type type) { - int first = 0, last = nr_deltas; + int first = 0, last = nr_ofs_deltas; - while (first < last) { - int next = (first + last) / 2; - struct delta_entry *delta = &deltas[next]; - int cmp; + while (first < last) { + int next = (first + last) / 2; + struct ofs_delta_entry *delta = &ofs_deltas[next]; + int cmp; - cmp = compare_delta_bases(base, &delta->base, - type, objects[delta->obj_no].type); - if (!cmp) - return next; - if (cmp < 0) { - last = next; - continue; - } - first = next+1; - } - return -first-1; + cmp = compare_ofs_delta_bases(offset, delta->offset, + type, objects[delta->obj_no].type); + if (!cmp) + return next; + if (cmp < 0) { + last = next; + continue; + } + first = next+1; + } + return -first-1; } -static void find_delta_children(const union delta_base *base, - int *first_index, int *last_index, - enum object_type type) +static void find_ofs_delta_children(off_t offset, + int *first_index, int *last_index, + enum object_type type) { - int first = find_delta(base, type); + int first = find_ofs_delta(offset, type); int last = first; - int end = nr_deltas - 1; + int end = nr_ofs_deltas - 1; if (first < 0) { *first_index = 0; *last_index = -1; return; } - while (first > 0 && !memcmp(&deltas[first - 1].base, base, UNION_BASE_SZ)) + while (first > 0 && ofs_deltas[first - 1].offset == offset) --first; - while (last < end && !memcmp(&deltas[last + 1].base, base, UNION_BASE_SZ)) + while (last < end && ofs_deltas[last + 1].offset == offset) + ++last; + *first_index = first; + *last_index = last; +} + +static int compare_ref_delta_bases(const unsigned char *sha1, + const unsigned char *sha2, + enum object_type type1, + enum object_type type2) +{ + int cmp = type1 - type2; + if (cmp) + return cmp; + return hashcmp(sha1, sha2); +} + +static int find_ref_delta(const unsigned char *sha1, enum object_type type) +{ + int first = 0, last = nr_ref_deltas; + + while (first < last) { + int next = (first + last) / 2; + struct ref_delta_entry *delta = &ref_deltas[next]; + int cmp; + + cmp = compare_ref_delta_bases(sha1, delta->sha1, + type, objects[delta->obj_no].type); + if (!cmp) + return next; + if (cmp < 0) { + last = next; + continue; + } + first = next+1; + } + return -first-1; +} + +static void find_ref_delta_children(const unsigned char *sha1, + int *first_index, int *last_index, + enum object_type type) +{ + int first = find_ref_delta(sha1, type); + int last = first; + int end = nr_ref_deltas - 1; + + if (first < 0) { + *first_index = 0; + *last_index = -1; + return; + } + while (first > 0 && !hashcmp(ref_deltas[first - 1].sha1, sha1)) + --first; + while (last < end && !hashcmp(ref_deltas[last + 1].sha1, sha1)) ++last; *first_index = first; *last_index = last; @@ -927,16 +977,13 @@ static struct base_data *find_unresolved_deltas_1(struct base_data *base, struct base_data *prev_base) { if (base->ref_last == -1 && base->ofs_last == -1) { - union delta_base base_spec; + find_ref_delta_children(base->obj->idx.sha1, + &base->ref_first, &base->ref_last, + OBJ_REF_DELTA); - hashcpy(base_spec.sha1, base->obj->idx.sha1); - find_delta_children(&base_spec, - &base->ref_first, &base->ref_last, OBJ_REF_DELTA); - - memset(&base_spec, 0, sizeof(base_spec)); - base_spec.offset = base->obj->idx.offset; - find_delta_children(&base_spec, - &base->ofs_first, &base->ofs_last, OBJ_OFS_DELTA); + find_ofs_delta_children(base->obj->idx.offset, + &base->ofs_first, &base->ofs_last, + OBJ_OFS_DELTA); if (base->ref_last == -1 && base->ofs_last == -1) { free(base->data); @@ -947,7 +994,7 @@ static struct base_data *find_unresolved_deltas_1(struct base_data *base, } if (base->ref_first <= base->ref_last) { - struct object_entry *child = objects + deltas[base->ref_first].obj_no; + struct object_entry *child = objects + ref_deltas[base->ref_first].obj_no; struct base_data *result = alloc_base_data(); if (!compare_and_swap_type(&child->real_type, OBJ_REF_DELTA, @@ -963,7 +1010,7 @@ static struct base_data *find_unresolved_deltas_1(struct base_data *base, } if (base->ofs_first <= base->ofs_last) { - struct object_entry *child = objects + deltas[base->ofs_first].obj_no; + struct object_entry *child = objects + ofs_deltas[base->ofs_first].obj_no; struct base_data *result = alloc_base_data(); assert(child->real_type == OBJ_OFS_DELTA); @@ -999,15 +1046,20 @@ static void find_unresolved_deltas(struct base_data *base) } } -static int compare_delta_entry(const void *a, const void *b) +static int compare_ofs_delta_entry(const void *a, const void *b) { - const struct delta_entry *delta_a = a; - const struct delta_entry *delta_b = b; + const struct ofs_delta_entry *delta_a = a; + const struct ofs_delta_entry *delta_b = b; - /* group by type (ref vs ofs) and then by value (sha-1 or offset) */ - return compare_delta_bases(&delta_a->base, &delta_b->base, - objects[delta_a->obj_no].type, - objects[delta_b->obj_no].type); + return delta_a->offset - delta_b->offset; +} + +static int compare_ref_delta_entry(const void *a, const void *b) +{ + const struct ref_delta_entry *delta_a = a; + const struct ref_delta_entry *delta_b = b; + + return hashcmp(delta_a->sha1, delta_b->sha1); } static void resolve_base(struct object_entry *obj) @@ -1053,7 +1105,8 @@ static void *threaded_second_pass(void *data) static void parse_pack_objects(unsigned char *sha1) { int i, nr_delays = 0; - struct delta_entry *delta = deltas; + struct ofs_delta_entry *ofs_delta = ofs_deltas; + unsigned char ref_delta_sha1[20]; struct stat st; if (verbose) @@ -1062,12 +1115,18 @@ static void parse_pack_objects(unsigned char *sha1) nr_objects); for (i = 0; i < nr_objects; i++) { struct object_entry *obj = &objects[i]; - void *data = unpack_raw_entry(obj, &delta->base, obj->idx.sha1); + void *data = unpack_raw_entry(obj, &ofs_delta->offset, + ref_delta_sha1, obj->idx.sha1); obj->real_type = obj->type; - if (is_delta_type(obj->type)) { - nr_deltas++; - delta->obj_no = i; - delta++; + if (obj->type == OBJ_OFS_DELTA) { + nr_ofs_deltas++; + ofs_delta->obj_no = i; + ofs_delta++; + } else if (obj->type == OBJ_REF_DELTA) { + ALLOC_GROW(ref_deltas, nr_ref_deltas + 1, ref_deltas_alloc); + hashcpy(ref_deltas[nr_ref_deltas].sha1, ref_delta_sha1); + ref_deltas[nr_ref_deltas].obj_no = i; + nr_ref_deltas++; } else if (!data) { /* large blobs, check later */ obj->real_type = OBJ_BAD; @@ -1118,15 +1177,18 @@ static void resolve_deltas(void) { int i; - if (!nr_deltas) + if (!nr_ofs_deltas && !nr_ref_deltas) return; /* Sort deltas by base SHA1/offset for fast searching */ - qsort(deltas, nr_deltas, sizeof(struct delta_entry), - compare_delta_entry); + qsort(ofs_deltas, nr_ofs_deltas, sizeof(struct ofs_delta_entry), + compare_ofs_delta_entry); + qsort(ref_deltas, nr_ref_deltas, sizeof(struct ref_delta_entry), + compare_ref_delta_entry); if (verbose) - progress = start_progress(_("Resolving deltas"), nr_deltas); + progress = start_progress(_("Resolving deltas"), + nr_ref_deltas + nr_ofs_deltas); #ifndef NO_PTHREADS nr_dispatched = 0; @@ -1164,7 +1226,7 @@ static void resolve_deltas(void) static void fix_unresolved_deltas(struct sha1file *f, int nr_unresolved); static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned char *pack_sha1) { - if (nr_deltas == nr_resolved_deltas) { + if (nr_ref_deltas + nr_ofs_deltas == nr_resolved_deltas) { stop_progress(&progress); /* Flush remaining pack final 20-byte SHA1. */ flush(); @@ -1175,7 +1237,7 @@ static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned cha struct sha1file *f; unsigned char read_sha1[20], tail_sha1[20]; struct strbuf msg = STRBUF_INIT; - int nr_unresolved = nr_deltas - nr_resolved_deltas; + int nr_unresolved = nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas; int nr_objects_initial = nr_objects; if (nr_unresolved <= 0) die(_("confusion beyond insanity")); @@ -1197,11 +1259,11 @@ static void conclude_pack(int fix_thin_pack, const char *curr_pack, unsigned cha die(_("Unexpected tail checksum for %s " "(disk corruption?)"), curr_pack); } - if (nr_deltas != nr_resolved_deltas) + if (nr_ofs_deltas + nr_ref_deltas != nr_resolved_deltas) die(Q_("pack has %d unresolved delta", "pack has %d unresolved deltas", - nr_deltas - nr_resolved_deltas), - nr_deltas - nr_resolved_deltas); + nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas), + nr_ofs_deltas + nr_ref_deltas - nr_resolved_deltas); } static int write_compressed(struct sha1file *f, void *in, unsigned int size) @@ -1261,14 +1323,14 @@ static struct object_entry *append_obj_to_pack(struct sha1file *f, static int delta_pos_compare(const void *_a, const void *_b) { - struct delta_entry *a = *(struct delta_entry **)_a; - struct delta_entry *b = *(struct delta_entry **)_b; + struct ref_delta_entry *a = *(struct ref_delta_entry **)_a; + struct ref_delta_entry *b = *(struct ref_delta_entry **)_b; return a->obj_no - b->obj_no; } static void fix_unresolved_deltas(struct sha1file *f, int nr_unresolved) { - struct delta_entry **sorted_by_pos; + struct ref_delta_entry **sorted_by_pos; int i, n = 0; /* @@ -1282,28 +1344,25 @@ static void fix_unresolved_deltas(struct sha1file *f, int nr_unresolved) * resolving deltas in the same order as their position in the pack. */ sorted_by_pos = xmalloc(nr_unresolved * sizeof(*sorted_by_pos)); - for (i = 0; i < nr_deltas; i++) { - if (objects[deltas[i].obj_no].real_type != OBJ_REF_DELTA) - continue; - sorted_by_pos[n++] = &deltas[i]; - } + for (i = 0; i < nr_ref_deltas; i++) + sorted_by_pos[n++] = &ref_deltas[i]; qsort(sorted_by_pos, n, sizeof(*sorted_by_pos), delta_pos_compare); for (i = 0; i < n; i++) { - struct delta_entry *d = sorted_by_pos[i]; + struct ref_delta_entry *d = sorted_by_pos[i]; enum object_type type; struct base_data *base_obj = alloc_base_data(); if (objects[d->obj_no].real_type != OBJ_REF_DELTA) continue; - base_obj->data = read_sha1_file(d->base.sha1, &type, &base_obj->size); + base_obj->data = read_sha1_file(d->sha1, &type, &base_obj->size); if (!base_obj->data) continue; - if (check_sha1_signature(d->base.sha1, base_obj->data, + if (check_sha1_signature(d->sha1, base_obj->data, base_obj->size, typename(type))) - die(_("local object %s is corrupt"), sha1_to_hex(d->base.sha1)); - base_obj->obj = append_obj_to_pack(f, d->base.sha1, + die(_("local object %s is corrupt"), sha1_to_hex(d->sha1)); + base_obj->obj = append_obj_to_pack(f, d->sha1, base_obj->data, base_obj->size, type); find_unresolved_deltas(base_obj); display_progress(progress, nr_resolved_deltas); @@ -1495,7 +1554,7 @@ static void read_idx_option(struct pack_idx_option *opts, const char *pack_name) static void show_pack_info(int stat_only) { - int i, baseobjects = nr_objects - nr_deltas; + int i, baseobjects = nr_objects - nr_ref_deltas - nr_ofs_deltas; unsigned long *chain_histogram = NULL; if (deepest_delta) @@ -1680,11 +1739,12 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix) objects = xcalloc(nr_objects + 1, sizeof(struct object_entry)); if (show_stat) obj_stat = xcalloc(nr_objects + 1, sizeof(struct object_stat)); - deltas = xcalloc(nr_objects, sizeof(struct delta_entry)); + ofs_deltas = xcalloc(nr_objects, sizeof(struct ofs_delta_entry)); parse_pack_objects(pack_sha1); resolve_deltas(); conclude_pack(fix_thin_pack, curr_pack, pack_sha1); - free(deltas); + free(ofs_deltas); + free(ref_deltas); if (strict) foreign_nr = check_objects();