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-rw-r--r--lib/slab.c128
1 files changed, 61 insertions, 67 deletions
diff --git a/lib/slab.c b/lib/slab.c
index f31355e0..b0a01ae7 100644
--- a/lib/slab.c
+++ b/lib/slab.c
@@ -4,6 +4,7 @@
* Heavily inspired by the original SLAB paper by Jeff Bonwick.
*
* (c) 1998--2000 Martin Mares <mj@ucw.cz>
+ * (c) 2020 Maria Matejka <mq@jmq.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
@@ -147,12 +148,12 @@ slab_memsize(resource *r)
* Real efficient version.
*/
-#define SLAB_SIZE 4096
#define MAX_EMPTY_HEADS 1
struct slab {
resource r;
- uint obj_size, head_size, objs_per_slab, num_empty_heads, data_size;
+ uint obj_size, head_size, head_bitfield_len;
+ uint objs_per_slab, num_empty_heads, data_size;
list empty_heads, partial_heads, full_heads;
};
@@ -167,16 +168,8 @@ static struct resclass sl_class = {
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;
+ u32 num_full;
+ u32 used_bits[0];
};
struct sl_alignment { /* Magic structure for testing of alignment */
@@ -184,6 +177,8 @@ struct sl_alignment { /* Magic structure for testing of alignment */
int x[0];
};
+#define SL_GET_HEAD(x) ((struct sl_head *) (((uintptr_t) (x)) & ~(get_page_size()-1)))
+
/**
* sl_new - create a new Slab
* @p: resource pool
@@ -200,45 +195,32 @@ sl_new(pool *p, uint size)
if (align < sizeof(int))
align = sizeof(int);
s->data_size = size;
- 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;
+
+ s->head_size = sizeof(struct sl_head);
+ u64 page_size = get_page_size();
+
+ do {
+ s->objs_per_slab = (page_size - s->head_size) / size;
+ s->head_bitfield_len = (s->objs_per_slab + 31) / 32;
+ s->head_size = (
+ sizeof(struct sl_head)
+ + sizeof(u32) * s->head_bitfield_len
+ + align - 1)
+ / align * align;
+ } while (s->objs_per_slab * size + s->head_size > page_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;
}
-static 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;
- uint n = s->objs_per_slab;
-
- *h = (struct sl_head) {
- .first_free = o,
- .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;
-}
-
/**
* sl_alloc - allocate an object from Slab
* @s: slab
@@ -250,24 +232,29 @@ 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++;
+ for (uint i=0; i<s->head_bitfield_len; i++)
+ if (~h->used_bits[i])
+ {
+ uint pos = u32_ctz(~h->used_bits[i]);
+ if (i * 32 + pos >= s->objs_per_slab)
+ break;
+
+ h->used_bits[i] |= 1 << pos;
+ h->num_full++;
+
+ void *out = ((void *) h) + s->head_size + (i * 32 + pos) * s->obj_size;
#ifdef POISON
- memset(o->u.data, 0xcd, s->data_size);
+ memset(out, 0xcd, s->data_size);
#endif
- return o->u.data;
+ return out;
+ }
-full_partial:
rem_node(&h->n);
add_tail(&s->full_heads, &h->n);
goto redo;
@@ -281,7 +268,9 @@ no_partial:
s->num_empty_heads--;
goto okay;
}
- h = sl_new_head(s);
+ h = alloc_page();
+ ASSERT_DIE(SL_GET_HEAD(h) == h);
+ memset(h, 0, s->head_size);
add_head(&s->partial_heads, &h->n);
goto okay;
}
@@ -313,30 +302,35 @@ sl_allocz(slab *s)
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;
+ struct sl_head *h = SL_GET_HEAD(oo);
#ifdef POISON
memset(oo, 0xdb, s->data_size);
#endif
- o->u.next = h->first_free;
- h->first_free = o;
- if (!--h->num_full)
+
+ uint offset = oo - ((void *) h) - s->head_size;
+ ASSERT_DIE(offset % s->obj_size == 0);
+ uint pos = offset / s->obj_size;
+ ASSERT_DIE(pos < s->objs_per_slab);
+
+ h->used_bits[pos / 32] &= ~(1 << (pos % 32));
+
+ if (h->num_full-- == s->objs_per_slab)
+ {
+ rem_node(&h->n);
+ add_head(&s->partial_heads, &h->n);
+ }
+ else if (!h->num_full)
{
rem_node(&h->n);
if (s->num_empty_heads >= MAX_EMPTY_HEADS)
- xfree(h);
+ free_page(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
@@ -346,11 +340,11 @@ slab_free(resource *r)
struct sl_head *h, *g;
WALK_LIST_DELSAFE(h, g, s->empty_heads)
- xfree(h);
+ free_page(h);
WALK_LIST_DELSAFE(h, g, s->partial_heads)
- xfree(h);
+ free_page(h);
WALK_LIST_DELSAFE(h, g, s->full_heads)
- xfree(h);
+ free_page(h);
}
static void
@@ -383,7 +377,7 @@ slab_memsize(resource *r)
WALK_LIST(h, s->full_heads)
heads++;
- return ALLOC_OVERHEAD + sizeof(struct slab) + heads * (ALLOC_OVERHEAD + SLAB_SIZE);
+ return ALLOC_OVERHEAD + sizeof(struct slab) + heads * (ALLOC_OVERHEAD + get_page_size());
}
static resource *
@@ -393,10 +387,10 @@ slab_lookup(resource *r, unsigned long a)
struct sl_head *h;
WALK_LIST(h, s->partial_heads)
- if ((unsigned long) h < a && (unsigned long) h + SLAB_SIZE < a)
+ if ((unsigned long) h < a && (unsigned long) h + get_page_size() < a)
return r;
WALK_LIST(h, s->full_heads)
- if ((unsigned long) h < a && (unsigned long) h + SLAB_SIZE < a)
+ if ((unsigned long) h < a && (unsigned long) h + get_page_size() < a)
return r;
return NULL;
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-27 09:11:35 +0000