diff options
Diffstat (limited to 'lib/slab.c')
| -rw-r--r-- | lib/slab.c | 209 |
1 files changed, 197 insertions, 12 deletions
@@ -1,7 +1,9 @@ /* - * BIRD Resource Manager -- SLABs + * BIRD Resource Manager -- A SLAB-like Memory Allocator * - * (c) 1998 Martin Mares <mj@ucw.cz> + * Heavily inspired by the original SLAB paper by Jeff Bonwick. + * + * (c) 1998--2000 Martin Mares <mj@ucw.cz> * * Can be freely distributed and used under the terms of the GNU GPL. */ @@ -12,31 +14,35 @@ #include "nest/bird.h" #include "lib/resource.h" +#undef FAKE_SLAB /* Turn on if you want to debug memory allocations */ + +static void slab_free(resource *r); +static void slab_dump(resource *r); + +#ifdef FAKE_SLAB + /* - * These are only fake, soon to change... + * Fake version used for debugging. */ -struct sl_obj { - node n; - byte data[0]; -}; - struct slab { resource r; unsigned size; list objs; }; -static void slab_free(resource *r); -static void slab_dump(resource *r); - static struct resclass sl_class = { - "Slab", + "FakeSlab", sizeof(struct slab), slab_free, slab_dump }; +struct sl_obj { + node n; + byte data[0]; +}; + slab * sl_new(pool *p, unsigned size) { @@ -85,3 +91,182 @@ slab_dump(resource *r) cnt++; debug("(%d objects per %d bytes)\n", cnt, s->size); } + +#else + +/* + * Real efficient version. + */ + +#define SLAB_SIZE 4096 +#define MAX_EMPTY_HEADS 1 + +struct slab { + resource r; + unsigned obj_size, head_size, objs_per_slab, num_empty_heads; + list empty_heads, partial_heads, full_heads; +}; + +static struct resclass sl_class = { + "Slab", + sizeof(struct slab), + slab_free, + slab_dump +}; + +struct sl_head { + node n; + struct sl_obj *first_free; + int num_full; +}; + +struct sl_obj { + struct sl_head *slab; + union { + struct sl_obj *next; + byte data[0]; + } u; +}; + +struct sl_alignment { /* Magic structure for testing of alignment */ + byte data; + int x[0]; +}; + +slab * +sl_new(pool *p, unsigned size) +{ + slab *s = ralloc(p, &sl_class); + unsigned int align = sizeof(struct sl_alignment); + if (align < sizeof(int)) + align = sizeof(int); + size += OFFSETOF(struct sl_obj, u.data); + if (size < sizeof(struct sl_obj)) + size = sizeof(struct sl_obj); + size = (size + align - 1) / align * align; + s->obj_size = size; + s->head_size = (sizeof(struct sl_head) + align - 1) / align * align; + s->objs_per_slab = (SLAB_SIZE - s->head_size) / size; + if (!s->objs_per_slab) + bug("Slab: object too large"); + s->num_empty_heads = 0; + init_list(&s->empty_heads); + init_list(&s->partial_heads); + init_list(&s->full_heads); + return s; +} + +struct sl_head * +sl_new_head(slab *s) +{ + struct sl_head *h = xmalloc(SLAB_SIZE); + struct sl_obj *o = (struct sl_obj *)((byte *)h+s->head_size); + struct sl_obj *no; + unsigned int n = s->objs_per_slab; + + h->first_free = o; + h->num_full = 0; + while (n--) + { + o->slab = h; + no = (struct sl_obj *)((char *) o+s->obj_size); + o->u.next = n ? no : NULL; + o = no; + } + return h; +} + +void * +sl_alloc(slab *s) +{ + struct sl_head *h; + struct sl_obj *o; + +redo: + h = HEAD(s->partial_heads); + if (!h->n.next) + goto no_partial; +okay: + o = h->first_free; + if (!o) + goto full_partial; + h->first_free = o->u.next; + h->num_full++; + return o->u.data; + +full_partial: + rem_node(&h->n); + add_tail(&s->full_heads, &h->n); + goto redo; + +no_partial: + h = HEAD(s->empty_heads); + if (h->n.next) + { + rem_node(&h->n); + add_head(&s->partial_heads, &h->n); + s->num_empty_heads--; + goto okay; + } + h = sl_new_head(s); + add_head(&s->partial_heads, &h->n); + goto okay; +} + +void +sl_free(slab *s, void *oo) +{ + struct sl_obj *o = SKIP_BACK(struct sl_obj, u.data, oo); + struct sl_head *h = o->slab; + + o->u.next = h->first_free; + h->first_free = o; + if (!--h->num_full) + { + rem_node(&h->n); + if (s->num_empty_heads >= MAX_EMPTY_HEADS) + xfree(h); + else + { + add_head(&s->empty_heads, &h->n); + s->num_empty_heads++; + } + } + else if (!o->u.next) + { + rem_node(&h->n); + add_head(&s->partial_heads, &h->n); + } +} + +static void +slab_free(resource *r) +{ + slab *s = (slab *) r; + struct sl_head *h, *g; + + WALK_LIST_DELSAFE(h, g, s->empty_heads) + xfree(h); + WALK_LIST_DELSAFE(h, g, s->partial_heads) + xfree(h); + WALK_LIST_DELSAFE(h, g, s->full_heads) + xfree(h); +} + +static void +slab_dump(resource *r) +{ + slab *s = (slab *) r; + int ec=0, pc=0, fc=0; + struct sl_head *h; + + WALK_LIST(h, s->empty_heads) + ec++; + WALK_LIST(h, s->partial_heads) + pc++; + WALK_LIST(h, s->full_heads) + fc++; + debug("(%de+%dp+%df blocks per %d objs per %d bytes)\n", ec, pc, fc, s->objs_per_slab, s->obj_size); +} + +#endif |