alloc.c

   1 /*
   2  * alloc.c  - specialized allocator for internal objects
   3  *
   4  * Copyright (C) 2006 Linus Torvalds
   5  *
   6  * The standard malloc/free wastes too much space for objects, partly because
   7  * it maintains all the allocation infrastructure (which isn't needed, since
   8  * we never free an object descriptor anyway), but even more because it ends
   9  * up with maximal alignment because it doesn't know what the object alignment
  10  * for the new allocation is.
  11  */
  12 #include "cache.h"
  13 #include "object.h"
  14 #include "blob.h"
  15 #include "tree.h"
  16 #include "commit.h"
  17 #include "tag.h"
  18
  19 #define BLOCKING 1024
  20
  21 union any_object {
  22         struct object object;
  23         struct blob blob;
  24         struct tree tree;
  25         struct commit commit;
  26         struct tag tag;
  27 };
  28
  29 struct alloc_state {
  30         int count; /* total number of nodes allocated */
  31         int nr;    /* number of nodes left in current allocation */
  32         void *p;   /* first free node in current allocation */
  33 };
  34
  35 static inline void *alloc_node(struct alloc_state *s, size_t node_size)
  36 {
  37         void *ret;
  38
  39         if (!s->nr) {
  40                 s->nr = BLOCKING;
  41                 s->p = xmalloc(BLOCKING * node_size);
  42         }
  43         s->nr--;
  44         s->count++;
  45         ret = s->p;
  46         s->p = (char *)s->p + node_size;
  47         memset(ret, 0, node_size);
  48         return ret;
  49 }
  50
  51 static struct alloc_state blob_state;
  52 void *alloc_blob_node(void)
  53 {
  54         struct blob *b = alloc_node(&blob_state, sizeof(struct blob));
  55         b->object.type = OBJ_BLOB;
  56         return b;
  57 }
  58
  59 static struct alloc_state tree_state;
  60 void *alloc_tree_node(void)
  61 {
  62         struct tree *t = alloc_node(&tree_state, sizeof(struct tree));
  63         t->object.type = OBJ_TREE;
  64         return t;
  65 }
  66
  67 static struct alloc_state tag_state;
  68 void *alloc_tag_node(void)
  69 {
  70         struct tag *t = alloc_node(&tag_state, sizeof(struct tag));
  71         t->object.type = OBJ_TAG;
  72         return t;
  73 }
  74
  75 static struct alloc_state object_state;
  76 void *alloc_object_node(void)
  77 {
  78         struct object *obj = alloc_node(&object_state, sizeof(union any_object));
  79         obj->type = OBJ_NONE;
  80         return obj;
  81 }
  82
  83 static struct alloc_state commit_state;
  84
  85 unsigned int alloc_commit_index(void)
  86 {
  87         static unsigned int count;
  88         return count++;
  89 }
  90
  91 void *alloc_commit_node(void)
  92 {
  93         struct commit *c = alloc_node(&commit_state, sizeof(struct commit));
  94         c->object.type = OBJ_COMMIT;
  95         c->index = alloc_commit_index();
  96         return c;
  97 }
  98
  99 static void report(const char *name, unsigned int count, size_t size)
 100 {
 101         fprintf(stderr, "%10s: %8u (%"PRIuMAX" kB)\n",
 102                         name, count, (uintmax_t) size);
 103 }
 104
 105 #define REPORT(name, type)      \
 106     report(#name, name##_state.count, name##_state.count * sizeof(type) >> 10)
 107
 108 void alloc_report(void)
 109 {
 110         REPORT(blob, struct blob);
 111         REPORT(tree, struct tree);
 112         REPORT(commit, struct commit);
 113         REPORT(tag, struct tag);
 114         REPORT(object, union any_object);
 115 }