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 #define DEFINE_ALLOCATOR(name, type)                            \
  22 static struct alloc_state name##_state;                         \
  23 void *alloc_##name##_node(void)                                 \
  24 {                                                               \
  25         return alloc_node(&name##_state, sizeof(type));         \
  26 }
  27
  28 union any_object {
  29         struct object object;
  30         struct blob blob;
  31         struct tree tree;
  32         struct commit commit;
  33         struct tag tag;
  34 };
  35
  36 struct alloc_state {
  37         int count; /* total number of nodes allocated */
  38         int nr;    /* number of nodes left in current allocation */
  39         void *p;   /* first free node in current allocation */
  40 };
  41
  42 static inline void *alloc_node(struct alloc_state *s, size_t node_size)
  43 {
  44         void *ret;
  45
  46         if (!s->nr) {
  47                 s->nr = BLOCKING;
  48                 s->p = xmalloc(BLOCKING * node_size);
  49         }
  50         s->nr--;
  51         s->count++;
  52         ret = s->p;
  53         s->p = (char *)s->p + node_size;
  54         memset(ret, 0, node_size);
  55         return ret;
  56 }
  57
  58 DEFINE_ALLOCATOR(blob, struct blob)
  59 DEFINE_ALLOCATOR(tree, struct tree)
  60 DEFINE_ALLOCATOR(tag, struct tag)
  61 DEFINE_ALLOCATOR(object, union any_object)
  62
  63 static struct alloc_state commit_state;
  64
  65 void *alloc_commit_node(void)
  66 {
  67         static int commit_count;
  68         struct commit *c = alloc_node(&commit_state, sizeof(struct commit));
  69         c->index = commit_count++;
  70         return c;
  71 }
  72
  73 static void report(const char *name, unsigned int count, size_t size)
  74 {
  75         fprintf(stderr, "%10s: %8u (%"PRIuMAX" kB)\n",
  76                         name, count, (uintmax_t) size);
  77 }
  78
  79 #define REPORT(name, type)      \
  80     report(#name, name##_state.count, name##_state.count * sizeof(type) >> 10)
  81
  82 void alloc_report(void)
  83 {
  84         REPORT(blob, struct blob);
  85         REPORT(tree, struct tree);
  86         REPORT(commit, struct commit);
  87         REPORT(tag, struct tag);
  88         REPORT(object, union any_object);
  89 }