pack-objects.h

   1 #ifndef PACK_OBJECTS_H
   2 #define PACK_OBJECTS_H
   3
   4 #include "odb.h"
   5 #include "thread-utils.h"
   6 #include "pack.h"
   7 #include "packfile.h"
   8
   9 struct repository;
  10
  11 #define DEFAULT_DELTA_CACHE_SIZE       (256 * 1024 * 1024)
  12 #define DEFAULT_DELTA_BASE_CACHE_LIMIT (96 * 1024 * 1024)
  13
  14 #define OE_DFS_STATE_BITS       2
  15 #define OE_DEPTH_BITS           12
  16 #define OE_IN_PACK_BITS         10
  17 #define OE_Z_DELTA_BITS         20
  18 /*
  19  * Note that oe_set_size() becomes expensive when the given size is
  20  * above this limit. Don't lower it too much.
  21  */
  22 #define OE_SIZE_BITS            31
  23 #define OE_DELTA_SIZE_BITS      23
  24
  25 /*
  26  * State flags for depth-first search used for analyzing delta cycles.
  27  *
  28  * The depth is measured in delta-links to the base (so if A is a delta
  29  * against B, then A has a depth of 1, and B a depth of 0).
  30  */
  31 enum dfs_state {
  32         DFS_NONE = 0,
  33         DFS_ACTIVE,
  34         DFS_DONE,
  35         DFS_NUM_STATES
  36 };
  37
  38 /*
  39  * The size of struct nearly determines pack-objects's memory
  40  * consumption. This struct is packed tight for that reason. When you
  41  * add or reorder something in this struct, think a bit about this.
  42  *
  43  * basic object info
  44  * -----------------
  45  * idx.oid is filled up before delta searching starts. idx.crc32 is
  46  * only valid after the object is written out and will be used for
  47  * generating the index. idx.offset will be both gradually set and
  48  * used in writing phase (base objects get offset first, then deltas
  49  * refer to them)
  50  *
  51  * "size" is the uncompressed object size. Compressed size of the raw
  52  * data for an object in a pack is not stored anywhere but is computed
  53  * and made available when reverse .idx is made. Note that when a
  54  * delta is reused, "size" is the uncompressed _delta_ size, not the
  55  * canonical one after the delta has been applied.
  56  *
  57  * "hash" contains a path name hash which is used for sorting the
  58  * delta list and also during delta searching. Once prepare_pack()
  59  * returns it's no longer needed.
  60  *
  61  * source pack info
  62  * ----------------
  63  * The (in_pack, in_pack_offset) tuple contains the location of the
  64  * object in the source pack. in_pack_header_size allows quickly
  65  * skipping the header and going straight to the zlib stream.
  66  *
  67  * "type" and "in_pack_type" both describe object type. in_pack_type
  68  * may contain a delta type, while type is always the canonical type.
  69  *
  70  * deltas
  71  * ------
  72  * Delta links (delta, delta_child and delta_sibling) are created to
  73  * reflect that delta graph from the source pack then updated or added
  74  * during delta searching phase when we find better deltas.
  75  *
  76  * delta_child and delta_sibling are last needed in
  77  * compute_write_order(). "delta" and "delta_size" must remain valid
  78  * at object writing phase in case the delta is not cached.
  79  *
  80  * If a delta is cached in memory and is compressed, delta_data points
  81  * to the data and z_delta_size contains the compressed size. If it's
  82  * uncompressed [1], z_delta_size must be zero. delta_size is always
  83  * the uncompressed size and must be valid even if the delta is not
  84  * cached.
  85  *
  86  * [1] during try_delta phase we don't bother with compressing because
  87  * the delta could be quickly replaced with a better one.
  88  */
  89 struct object_entry {
  90         struct pack_idx_entry idx;
  91         void *delta_data;       /* cached delta (uncompressed) */
  92         off_t in_pack_offset;
  93         uint32_t hash;                  /* name hint hash */
  94         unsigned size_:OE_SIZE_BITS;
  95         unsigned size_valid:1;
  96         uint32_t delta_idx;     /* delta base object */
  97         uint32_t delta_child_idx; /* deltified objects who bases me */
  98         uint32_t delta_sibling_idx; /* other deltified objects who
  99                                      * uses the same base as me
 100                                      */
 101         unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
 102         unsigned delta_size_valid:1;
 103         unsigned char in_pack_header_size;
 104         unsigned in_pack_idx:OE_IN_PACK_BITS;   /* already in pack */
 105         unsigned z_delta_size:OE_Z_DELTA_BITS;
 106         unsigned type_valid:1;
 107         unsigned no_try_delta:1;
 108         unsigned type_:TYPE_BITS;
 109         unsigned in_pack_type:TYPE_BITS; /* could be delta */
 110
 111         unsigned preferred_base:1; /*
 112                                     * we do not pack this, but is available
 113                                     * to be used as the base object to delta
 114                                     * objects against.
 115                                     */
 116         unsigned tagged:1; /* near the very tip of refs */
 117         unsigned filled:1; /* assigned write-order */
 118         unsigned dfs_state:OE_DFS_STATE_BITS;
 119         unsigned depth:OE_DEPTH_BITS;
 120         unsigned ext_base:1; /* delta_idx points outside packlist */
 121 };
 122
 123 /**
 124  * A packing region is a section of the packing_data.objects array
 125  * as given by a starting index and a number of elements.
 126  */
 127 struct packing_region {
 128         size_t start;
 129         size_t nr;
 130 };
 131
 132 struct packing_data {
 133         struct repository *repo;
 134         struct object_entry *objects;
 135         uint32_t nr_objects, nr_alloc;
 136
 137         struct packing_region *regions;
 138         size_t nr_regions, nr_regions_alloc;
 139
 140         int32_t *index;
 141         uint32_t index_size;
 142
 143         unsigned int *in_pack_pos;
 144         unsigned long *delta_size;
 145
 146         /*
 147          * Only one of these can be non-NULL and they have different
 148          * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
 149          * the pack of an object using in_pack_idx field. If not,
 150          * in_pack[] array is used the same way as in_pack_pos[]
 151          */
 152         struct packed_git **in_pack_by_idx;
 153         struct packed_git **in_pack;
 154
 155         /*
 156          * During packing with multiple threads, protect the in-core
 157          * object database from concurrent accesses.
 158          */
 159         pthread_mutex_t odb_lock;
 160
 161         /*
 162          * This list contains entries for bases which we know the other side
 163          * has (e.g., via reachability bitmaps), but which aren't in our
 164          * "objects" list.
 165          */
 166         struct object_entry *ext_bases;
 167         uint32_t nr_ext, alloc_ext;
 168
 169         uintmax_t oe_size_limit;
 170         uintmax_t oe_delta_size_limit;
 171
 172         /* delta islands */
 173         unsigned int *tree_depth;
 174         unsigned char *layer;
 175
 176         /*
 177          * Used when writing cruft packs.
 178          *
 179          * Object mtimes are stored in pack order when writing, but
 180          * written out in lexicographic (index) order.
 181          */
 182         uint32_t *cruft_mtime;
 183 };
 184
 185 void prepare_packing_data(struct repository *r, struct packing_data *pdata);
 186 void clear_packing_data(struct packing_data *pdata);
 187
 188 /* Protect access to object database */
 189 static inline void packing_data_lock(struct packing_data *pdata)
 190 {
 191         pthread_mutex_lock(&pdata->odb_lock);
 192 }
 193 static inline void packing_data_unlock(struct packing_data *pdata)
 194 {
 195         pthread_mutex_unlock(&pdata->odb_lock);
 196 }
 197
 198 struct object_entry *packlist_alloc(struct packing_data *pdata,
 199                                     const struct object_id *oid);
 200
 201 struct object_entry *packlist_find(struct packing_data *pdata,
 202                                    const struct object_id *oid);
 203
 204 static inline uint32_t pack_name_hash(const char *name)
 205 {
 206         uint32_t c, hash = 0;
 207
 208         if (!name)
 209                 return 0;
 210
 211         /*
 212          * This effectively just creates a sortable number from the
 213          * last sixteen non-whitespace characters. Last characters
 214          * count "most", so things that end in ".c" sort together.
 215          */
 216         while ((c = *name++) != 0) {
 217                 if (isspace(c))
 218                         continue;
 219                 hash = (hash >> 2) + (c << 24);
 220         }
 221         return hash;
 222 }
 223
 224 static inline uint32_t pack_name_hash_v2(const unsigned char *name)
 225 {
 226         uint32_t hash = 0, base = 0, c;
 227
 228         if (!name)
 229                 return 0;
 230
 231         while ((c = *name++)) {
 232                 if (isspace(c))
 233                         continue;
 234                 if (c == '/') {
 235                         base = (base >> 6) ^ hash;
 236                         hash = 0;
 237                 } else {
 238                         /*
 239                          * 'c' is only a single byte. Reverse it and move
 240                          * it to the top of the hash, moving the rest to
 241                          * less-significant bits.
 242                          */
 243                         c = (c & 0xF0) >> 4 | (c & 0x0F) << 4;
 244                         c = (c & 0xCC) >> 2 | (c & 0x33) << 2;
 245                         c = (c & 0xAA) >> 1 | (c & 0x55) << 1;
 246                         hash = (hash >> 2) + (c << 24);
 247                 }
 248         }
 249         return (base >> 6) ^ hash;
 250 }
 251
 252 static inline enum object_type oe_type(const struct object_entry *e)
 253 {
 254         return e->type_valid ? e->type_ : OBJ_BAD;
 255 }
 256
 257 static inline void oe_set_type(struct object_entry *e,
 258                                enum object_type type)
 259 {
 260         if (type >= OBJ_ANY)
 261                 BUG("OBJ_ANY cannot be set in pack-objects code");
 262
 263         e->type_valid = type >= OBJ_NONE;
 264         e->type_ = (unsigned)type;
 265 }
 266
 267 static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
 268                                           const struct object_entry *e)
 269 {
 270         return pack->in_pack_pos[e - pack->objects];
 271 }
 272
 273 static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 274                                       const struct object_entry *e,
 275                                       unsigned int pos)
 276 {
 277         pack->in_pack_pos[e - pack->objects] = pos;
 278 }
 279
 280 static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
 281                                             const struct object_entry *e)
 282 {
 283         if (pack->in_pack_by_idx)
 284                 return pack->in_pack_by_idx[e->in_pack_idx];
 285         else
 286                 return pack->in_pack[e - pack->objects];
 287 }
 288
 289 void oe_map_new_pack(struct packing_data *pack);
 290
 291 static inline void oe_set_in_pack(struct packing_data *pack,
 292                                   struct object_entry *e,
 293                                   struct packed_git *p)
 294 {
 295         if (pack->in_pack_by_idx) {
 296                 if (p->index) {
 297                         e->in_pack_idx = p->index;
 298                         return;
 299                 }
 300                 /*
 301                  * We're accessing packs by index, but this pack doesn't have
 302                  * an index (e.g., because it was added since we created the
 303                  * in_pack_by_idx array). Bail to oe_map_new_pack(), which
 304                  * will convert us to using the full in_pack array, and then
 305                  * fall through to our in_pack handling.
 306                  */
 307                 oe_map_new_pack(pack);
 308         }
 309         pack->in_pack[e - pack->objects] = p;
 310 }
 311
 312 void oe_set_delta_ext(struct packing_data *pack,
 313                       struct object_entry *e,
 314                       const struct object_id *oid);
 315
 316 static inline unsigned int oe_tree_depth(struct packing_data *pack,
 317                                          struct object_entry *e)
 318 {
 319         if (!pack->tree_depth)
 320                 return 0;
 321         return pack->tree_depth[e - pack->objects];
 322 }
 323
 324 static inline void oe_set_layer(struct packing_data *pack,
 325                                 struct object_entry *e,
 326                                 unsigned char layer)
 327 {
 328         if (!pack->layer)
 329                 CALLOC_ARRAY(pack->layer, pack->nr_alloc);
 330         pack->layer[e - pack->objects] = layer;
 331 }
 332
 333 static inline uint32_t oe_cruft_mtime(struct packing_data *pack,
 334                                       struct object_entry *e)
 335 {
 336         if (!pack->cruft_mtime)
 337                 return 0;
 338         return pack->cruft_mtime[e - pack->objects];
 339 }
 340
 341 static inline void oe_set_cruft_mtime(struct packing_data *pack,
 342                                       struct object_entry *e,
 343                                       uint32_t mtime)
 344 {
 345         if (!pack->cruft_mtime)
 346                 CALLOC_ARRAY(pack->cruft_mtime, pack->nr_alloc);
 347         pack->cruft_mtime[e - pack->objects] = mtime;
 348 }
 349
 350 #endif