#include <stdio.h>
#include <pthread.h>
-#define DEBUG /* Test */
+//#define DEBUG /* Test */
#ifdef DEBUG
#define dbg_printf(args...) printf(args)
#define dbg_printf(args...)
#endif
-#define CHAIN_LEN_TARGET 1
-#define CHAIN_LEN_RESIZE_THRESHOLD 2
+#define CHAIN_LEN_TARGET 4
+#define CHAIN_LEN_RESIZE_THRESHOLD 8
#ifndef max
#define max(a, b) ((a) > (b) ? (a) : (b))
#endif
+/*
+ * The removed flag needs to be updated atomically with the pointer.
+ * The dummy flag does not require to be updated atomically with the
+ * pointer, but it is added as a pointer low bit flag to save space.
+ */
#define REMOVED_FLAG (1UL << 0)
#define DUMMY_FLAG (1UL << 1)
#define FLAGS_MASK ((1UL << 2) - 1)
unsigned long resize_target;
int resize_initiated;
struct rcu_head head;
- struct rcu_ht_node *tbl[0];
+ struct _rcu_ht_node *tbl[0];
};
struct rcu_ht {
ht_compare_fct compare_fct;
unsigned long hash_seed;
pthread_mutex_t resize_mutex; /* resize mutex: add/del mutex */
- unsigned int in_progress_resize;
+ unsigned int in_progress_resize, in_progress_destroy;
void (*ht_call_rcu)(struct rcu_head *head,
void (*func)(struct rcu_head *head));
};
}
/*
- * Algorithm to find the log2 of a 32-bit unsigned integer.
- * source: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogLookup
- * Originally from Public Domain.
+ * fls: returns the position of the most significant bit.
+ * Returns 0 if no bit is set, else returns the position of the most
+ * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
*/
-static const char LogTable256[256] =
+#if defined(__i386) || defined(__x86_64)
+static inline
+unsigned int fls_u32(uint32_t x)
+{
+ int r;
+
+ asm("bsrl %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movl $-1,%0\n\t"
+ "1:\n\t"
+ : "=r" (r) : "rm" (x));
+ return r + 1;
+}
+#define HAS_FLS_U32
+#endif
+
+#if defined(__x86_64)
+static inline
+unsigned int fls_u64(uint64_t x)
{
-#define LT(n) n, n, n, n, n, n, n, n, n, n, n, n, n, n, n, n
- -1, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
- LT(4), LT(5), LT(5), LT(6), LT(6), LT(6), LT(6),
- LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7), LT(7)
-};
+ long r;
+
+ asm("bsrq %1,%0\n\t"
+ "jnz 1f\n\t"
+ "movq $-1,%0\n\t"
+ "1:\n\t"
+ : "=r" (r) : "rm" (x));
+ return r + 1;
+}
+#define HAS_FLS_U64
+#endif
+
+#ifndef HAS_FLS_U64
+static __attribute__((unused))
+unsigned int fls_u64(uint64_t x)
+{
+ unsigned int r = 64;
+
+ if (!x)
+ return 0;
+
+ if (!(x & 0xFFFFFFFF00000000ULL)) {
+ x <<= 32;
+ r -= 32;
+ }
+ if (!(x & 0xFFFF000000000000ULL)) {
+ x <<= 16;
+ r -= 16;
+ }
+ if (!(x & 0xFF00000000000000ULL)) {
+ x <<= 8;
+ r -= 8;
+ }
+ if (!(x & 0xF000000000000000ULL)) {
+ x <<= 4;
+ r -= 4;
+ }
+ if (!(x & 0xC000000000000000ULL)) {
+ x <<= 2;
+ r -= 2;
+ }
+ if (!(x & 0x8000000000000000ULL)) {
+ x <<= 1;
+ r -= 1;
+ }
+ return r;
+}
+#endif
+
+#ifndef HAS_FLS_U32
+static __attribute__((unused))
+unsigned int fls_u32(uint32_t x)
+{
+ unsigned int r = 32;
+
+ if (!x)
+ return 0;
+ if (!(x & 0xFFFF0000U)) {
+ x <<= 16;
+ r -= 16;
+ }
+ if (!(x & 0xFF000000U)) {
+ x <<= 8;
+ r -= 8;
+ }
+ if (!(x & 0xF0000000U)) {
+ x <<= 4;
+ r -= 4;
+ }
+ if (!(x & 0xC0000000U)) {
+ x <<= 2;
+ r -= 2;
+ }
+ if (!(x & 0x80000000U)) {
+ x <<= 1;
+ r -= 1;
+ }
+ return r;
+}
+#endif
-uint32_t log2_u32(uint32_t v)
+unsigned int fls_ulong(unsigned long x)
{
- uint32_t t, tt;
+#if (CAA_BITS_PER_lONG == 32)
+ return fls_u32(x);
+#else
+ return fls_u64(x);
+#endif
+}
+
+int get_count_order_u32(uint32_t x)
+{
+ int order;
- if ((tt = (v >> 16)))
- return (t = (tt >> 8))
- ? 24 + LogTable256[t]
- : 16 + LogTable256[tt];
- else
- return (t = (v >> 8))
- ? 8 + LogTable256[t]
- : LogTable256[v];
+ order = fls_u32(x) - 1;
+ if (x & (x - 1))
+ order++;
+ return order;
+}
+
+int get_count_order_ulong(unsigned long x)
+{
+ int order;
+
+ order = fls_ulong(x) - 1;
+ if (x & (x - 1))
+ order++;
+ return order;
}
static
void check_resize(struct rcu_ht *ht, struct rcu_table *t,
uint32_t chain_len)
{
+ if (chain_len > 100)
+ dbg_printf("rculfhash: WARNING: large chain length: %u.\n",
+ chain_len);
if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
ht_resize_lazy(ht, t,
- log2_u32(chain_len - CHAIN_LEN_TARGET - 1));
+ get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
}
static
next = rcu_dereference(clear_flag(iter)->p.next);
if (is_removed(next))
break;
- iter_prev = iter;
+ iter_prev = clear_flag(iter);
iter = next;
}
assert(!is_removed(iter));
{
struct rcu_ht_node *iter_prev, *iter, *next, *new_node, *new_next,
*dummy_node;
- unsigned long hash;
+ struct _rcu_ht_node *lookup;
+ unsigned long hash, index, order;
if (!t->size) {
- assert(node->p.dummy);
assert(dummy);
node->p.next = flag_dummy(NULL);
return node; /* Initial first add (head) */
* iter_prev points to the non-removed node prior to the
* insert location.
*/
- iter_prev = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+ index = hash & (t->size - 1);
+ order = get_count_order_ulong(index + 1);
+ lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
+ iter_prev = (struct rcu_ht_node *) lookup;
/* We can always skip the dummy node initially */
iter = rcu_dereference(iter_prev->p.next);
assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
if (is_removed(next))
goto gc_node;
if (unique
- && !clear_flag(iter)->p.dummy
+ && !is_dummy(next)
&& !ht->compare_fct(node->key, node->key_len,
clear_flag(iter)->key,
clear_flag(iter)->key_len))
return clear_flag(iter);
/* Only account for identical reverse hash once */
- if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash)
+ if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash
+ && !is_dummy(next))
check_resize(ht, t, ++chain_len);
iter_prev = clear_flag(iter);
iter = next;
assert(!is_removed(iter_prev));
assert(iter_prev != node);
if (!dummy)
- node->p.next = iter;
+ node->p.next = clear_flag(iter);
else
- node->p.next = flag_dummy(iter);
+ node->p.next = flag_dummy(clear_flag(iter));
if (is_dummy(iter))
new_node = flag_dummy(node);
else
}
gc_end:
/* Garbage collect logically removed nodes in the bucket */
- dummy_node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+ index = hash & (t->size - 1);
+ order = get_count_order_ulong(index + 1);
+ lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
+ dummy_node = (struct rcu_ht_node *) lookup;
_ht_gc_bucket(dummy_node, node);
return node;
}
int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
{
struct rcu_ht_node *dummy, *next, *old;
+ struct _rcu_ht_node *lookup;
int flagged = 0;
- unsigned long hash;
+ unsigned long hash, index, order;
/* logically delete the node */
old = rcu_dereference(node->p.next);
next = old;
if (is_removed(next))
goto end;
- assert(!node->p.dummy);
+ assert(!is_dummy(next));
old = uatomic_cmpxchg(&node->p.next, next,
flag_removed(next));
} while (old != next);
* if found.
*/
hash = bit_reverse_ulong(node->p.reverse_hash);
- dummy = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+ index = hash & (t->size - 1);
+ order = get_count_order_ulong(index + 1);
+ lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
+ dummy = (struct rcu_ht_node *) lookup;
_ht_gc_bucket(dummy, node);
end:
/*
static
void init_table(struct rcu_ht *ht, struct rcu_table *t,
- unsigned long first, unsigned long len)
-{
- unsigned long i, end;
-
- end = first + len;
- for (i = first; i < end; i++) {
- /* Update table size when power of two */
- if (i != 0 && !(i & (i - 1)))
- t->size = i;
- t->tbl[i] = calloc(1, sizeof(struct _rcu_ht_node));
- t->tbl[i]->p.dummy = 1;
- t->tbl[i]->p.reverse_hash = bit_reverse_ulong(i);
- (void) _ht_add(ht, t, t->tbl[i], 0, 1);
+ unsigned long first_order, unsigned long len_order)
+{
+ unsigned long i, end_order;
+
+ dbg_printf("rculfhash: init table: first_order %lu end_order %lu\n",
+ first_order, first_order + len_order);
+ end_order = first_order + len_order;
+ t->size = !first_order ? 0 : (1UL << (first_order - 1));
+ for (i = first_order; i < end_order; i++) {
+ unsigned long j, len;
+
+ len = !i ? 1 : 1UL << (i - 1);
+ dbg_printf("rculfhash: init order %lu len: %lu\n", i, len);
+ t->tbl[i] = calloc(len, sizeof(struct _rcu_ht_node));
+ for (j = 0; j < len; j++) {
+ dbg_printf("rculfhash: init entry: i %lu j %lu hash %lu\n",
+ i, j, !i ? 0 : (1UL << (i - 1)) + j);
+ struct rcu_ht_node *new_node =
+ (struct rcu_ht_node *) &t->tbl[i][j];
+ new_node->p.reverse_hash =
+ bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
+ (void) _ht_add(ht, t, new_node, 0, 1);
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+ break;
+ }
+ /* Update table size */
+ t->size = !i ? 1 : (1UL << i);
+ dbg_printf("rculfhash: init new size: %lu\n", t->size);
+ if (CMM_LOAD_SHARED(ht->in_progress_destroy))
+ break;
}
- t->resize_target = t->size = end;
+ t->resize_target = t->size;
t->resize_initiated = 0;
}
void (*func)(struct rcu_head *head)))
{
struct rcu_ht *ht;
+ unsigned long order;
ht = calloc(1, sizeof(struct rcu_ht));
ht->hash_fct = hash_fct;
ht->in_progress_resize = 0;
/* this mutex should not nest in read-side C.S. */
pthread_mutex_init(&ht->resize_mutex, NULL);
+ order = get_count_order_ulong(max(init_size, 1)) + 1;
ht->t = calloc(1, sizeof(struct rcu_table)
- + (max(init_size, 1) * sizeof(struct rcu_ht_node *)));
+ + (order * sizeof(struct _rcu_ht_node *)));
ht->t->size = 0;
pthread_mutex_lock(&ht->resize_mutex);
- init_table(ht, ht->t, 0, max(init_size, 1));
+ init_table(ht, ht->t, 0, order);
pthread_mutex_unlock(&ht->resize_mutex);
return ht;
}
struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
{
struct rcu_table *t;
- struct rcu_ht_node *node;
- unsigned long hash, reverse_hash;
+ struct rcu_ht_node *node, *next;
+ struct _rcu_ht_node *lookup;
+ unsigned long hash, reverse_hash, index, order;
hash = ht->hash_fct(key, key_len, ht->hash_seed);
reverse_hash = bit_reverse_ulong(hash);
t = rcu_dereference(ht->t);
- node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+ index = hash & (t->size - 1);
+ order = get_count_order_ulong(index + 1);
+ lookup = &t->tbl[order][index & ((1UL << (order - 1)) - 1)];
+ dbg_printf("rculfhash: lookup hash %lu index %lu order %lu aridx %lu\n",
+ hash, index, order, index & ((1UL << (order - 1)) - 1));
+ node = (struct rcu_ht_node *) lookup;
for (;;) {
if (unlikely(!node))
break;
node = NULL;
break;
}
- if (likely(!is_removed(rcu_dereference(node->p.next)))
- && !node->p.dummy
+ next = rcu_dereference(node->p.next);
+ if (likely(!is_removed(next))
+ && !is_dummy(next)
&& likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
break;
}
- node = clear_flag(rcu_dereference(node->p.next));
+ node = clear_flag(next);
}
- assert(!node || !node->p.dummy);
+ assert(!node || !is_dummy(rcu_dereference(node->p.next)));
return node;
}
{
struct rcu_table *t;
struct rcu_ht_node *node;
- unsigned long i;
+ struct _rcu_ht_node *lookup;
+ unsigned long order, i;
t = ht->t;
/* Check that the table is empty */
- node = t->tbl[0];
+ lookup = &t->tbl[0][0];
+ node = (struct rcu_ht_node *) lookup;
do {
- if (!node->p.dummy)
+ node = clear_flag(node)->p.next;
+ if (!is_dummy(node))
return -EPERM;
- node = node->p.next;
assert(!is_removed(node));
} while (clear_flag(node));
/* Internal sanity check: all nodes left should be dummy */
- for (i = 0; i < t->size; i++) {
- assert(t->tbl[i]->p.dummy);
- free(t->tbl[i]);
+ for (order = 0; order < get_count_order_ulong(t->size) + 1; order++) {
+ unsigned long len;
+
+ len = !order ? 1 : 1UL << (order - 1);
+ for (i = 0; i < len; i++) {
+ dbg_printf("rculfhash: delete order %lu i %lu hash %lu\n",
+ order, i,
+ bit_reverse_ulong(t->tbl[order][i].reverse_hash));
+ assert(is_dummy(t->tbl[order][i].next));
+ }
+ free(t->tbl[order]);
}
return 0;
}
int ret;
/* Wait for in-flight resize operations to complete */
+ CMM_STORE_SHARED(ht->in_progress_destroy, 1);
while (uatomic_read(&ht->in_progress_resize))
poll(NULL, 0, 100); /* wait for 100ms */
ret = ht_delete_dummy(ht);
{
struct rcu_table *t;
struct rcu_ht_node *node, *next;
+ struct _rcu_ht_node *lookup;
+ unsigned long nr_dummy = 0;
*count = 0;
*removed = 0;
t = rcu_dereference(ht->t);
- /* Check that the table is empty */
- node = rcu_dereference(t->tbl[0]);
+ /* Count non-dummy nodes in the table */
+ lookup = &t->tbl[0][0];
+ node = (struct rcu_ht_node *) lookup;
do {
next = rcu_dereference(node->p.next);
if (is_removed(next)) {
- assert(!node->p.dummy);
+ assert(!is_dummy(next));
(*removed)++;
- } else if (!node->p.dummy)
+ } else if (!is_dummy(next))
(*count)++;
+ else
+ (nr_dummy)++;
node = clear_flag(next);
} while (node);
+ dbg_printf("rculfhash: number of dummy nodes: %lu\n", nr_dummy);
}
static
static
void _do_ht_resize(struct rcu_ht *ht)
{
- unsigned long new_size, old_size;
+ unsigned long new_size, old_size, old_order, new_order;
struct rcu_table *new_t, *old_t;
old_t = ht->t;
old_size = old_t->size;
+ old_order = get_count_order_ulong(old_size) + 1;
new_size = CMM_LOAD_SHARED(old_t->resize_target);
- dbg_printf("rculfhash: resize from %lu to %lu buckets\n",
- old_size, new_size);
if (old_size == new_size)
return;
+ new_order = get_count_order_ulong(new_size) + 1;
+ printf("rculfhash: resize from %lu (order %lu) to %lu (order %lu) buckets\n",
+ old_size, old_order, new_size, new_order);
new_t = malloc(sizeof(struct rcu_table)
- + (new_size * sizeof(struct rcu_ht_node *)));
+ + (new_order * sizeof(struct _rcu_ht_node *)));
assert(new_size > old_size);
memcpy(&new_t->tbl, &old_t->tbl,
- old_size * sizeof(struct rcu_ht_node *));
- init_table(ht, new_t, old_size, new_size - old_size);
+ old_order * sizeof(struct _rcu_ht_node *));
+ init_table(ht, new_t, old_order, new_order - old_order);
/* Changing table and size atomically wrt lookups */
rcu_assign_pointer(ht->t, new_t);
ht->ht_call_rcu(&old_t->head, ht_free_table_cb);
projects / urcu.git / blobdiff