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authorDharmik Thakkar <dharmik.thakkar@arm.com>2019-04-02 19:44:54 +0000
committerThomas Monjalon <thomas@monjalon.net>2019-04-03 20:52:35 +0200
commitf401363d984a6958166d3e1648c4f282102d2218 (patch)
tree10e1a0725ea7a837a9f76899c4ba6afdab429cee
parent237060c4ad15b4ee9002be3c0e56ac3070eceb48 (diff)
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hash: support lock-free extendable bucket
This patch enables lock-free read-write concurrency support for extendable bucket feature. Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com> Reviewed-by: Gavin Hu <gavin.hu@arm.com> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> Acked-by: Yipeng Wang <yipeng1.wang@intel.com>
-rw-r--r--doc/guides/prog_guide/hash_lib.rst6
-rw-r--r--lib/librte_hash/rte_cuckoo_hash.c157
-rw-r--r--lib/librte_hash/rte_cuckoo_hash.h7
3 files changed, 117 insertions, 53 deletions
diff --git a/doc/guides/prog_guide/hash_lib.rst b/doc/guides/prog_guide/hash_lib.rst
index 85a6edf..d06c7de 100644
--- a/doc/guides/prog_guide/hash_lib.rst
+++ b/doc/guides/prog_guide/hash_lib.rst
@@ -108,9 +108,9 @@ Extendable Bucket Functionality support
An extra flag is used to enable this functionality (flag is not set by default). When the (RTE_HASH_EXTRA_FLAGS_EXT_TABLE) is set and
in the very unlikely case due to excessive hash collisions that a key has failed to be inserted, the hash table bucket is extended with a linked
list to insert these failed keys. This feature is important for the workloads (e.g. telco workloads) that need to insert up to 100% of the
-hash table size and can't tolerate any key insertion failure (even if very few). Currently the extendable bucket is not supported
-with the lock-free concurrency implementation (RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF).
-
+hash table size and can't tolerate any key insertion failure (even if very few).
+Please note that with the 'lock free read/write concurrency' flag enabled, users need to call 'rte_hash_free_key_with_position' API in order to free the empty buckets and
+deleted keys, to maintain the 100% capacity guarantee.
Implementation Details (non Extendable Bucket Case)
---------------------------------------------------
diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index 0dddce2..4fcf548 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -141,6 +141,7 @@ rte_hash_create(const struct rte_hash_parameters *params)
unsigned int readwrite_concur_support = 0;
unsigned int writer_takes_lock = 0;
unsigned int no_free_on_del = 0;
+ uint32_t *ext_bkt_to_free = NULL;
uint32_t *tbl_chng_cnt = NULL;
unsigned int readwrite_concur_lf_support = 0;
@@ -171,15 +172,6 @@ rte_hash_create(const struct rte_hash_parameters *params)
return NULL;
}
- if ((params->extra_flag & RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF) &&
- (params->extra_flag & RTE_HASH_EXTRA_FLAGS_EXT_TABLE)) {
- rte_errno = EINVAL;
- RTE_LOG(ERR, HASH, "rte_hash_create: extendable bucket "
- "feature not supported with rw concurrency "
- "lock free\n");
- return NULL;
- }
-
/* Check extra flags field to check extra options. */
if (params->extra_flag & RTE_HASH_EXTRA_FLAGS_TRANS_MEM_SUPPORT)
hw_trans_mem_support = 1;
@@ -303,6 +295,16 @@ rte_hash_create(const struct rte_hash_parameters *params)
*/
for (i = 1; i <= num_buckets; i++)
rte_ring_sp_enqueue(r_ext, (void *)((uintptr_t) i));
+
+ if (readwrite_concur_lf_support) {
+ ext_bkt_to_free = rte_zmalloc(NULL, sizeof(uint32_t) *
+ num_key_slots, 0);
+ if (ext_bkt_to_free == NULL) {
+ RTE_LOG(ERR, HASH, "ext bkt to free memory allocation "
+ "failed\n");
+ goto err_unlock;
+ }
+ }
}
const uint32_t key_entry_size =
@@ -394,6 +396,7 @@ rte_hash_create(const struct rte_hash_parameters *params)
default_hash_func : params->hash_func;
h->key_store = k;
h->free_slots = r;
+ h->ext_bkt_to_free = ext_bkt_to_free;
h->tbl_chng_cnt = tbl_chng_cnt;
*h->tbl_chng_cnt = 0;
h->hw_trans_mem_support = hw_trans_mem_support;
@@ -448,6 +451,7 @@ err:
rte_free(buckets_ext);
rte_free(k);
rte_free(tbl_chng_cnt);
+ rte_free(ext_bkt_to_free);
return NULL;
}
@@ -489,6 +493,7 @@ rte_hash_free(struct rte_hash *h)
rte_free(h->buckets);
rte_free(h->buckets_ext);
rte_free(h->tbl_chng_cnt);
+ rte_free(h->ext_bkt_to_free);
rte_free(h);
rte_free(te);
}
@@ -804,7 +809,7 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h,
__atomic_store_n(h->tbl_chng_cnt,
*h->tbl_chng_cnt + 1,
__ATOMIC_RELEASE);
- /* The stores to sig_alt and sig_current should not
+ /* The store to sig_current should not
* move above the store to tbl_chng_cnt.
*/
__atomic_thread_fence(__ATOMIC_RELEASE);
@@ -836,7 +841,7 @@ rte_hash_cuckoo_move_insert_mw(const struct rte_hash *h,
__atomic_store_n(h->tbl_chng_cnt,
*h->tbl_chng_cnt + 1,
__ATOMIC_RELEASE);
- /* The stores to sig_alt and sig_current should not
+ /* The store to sig_current should not
* move above the store to tbl_chng_cnt.
*/
__atomic_thread_fence(__ATOMIC_RELEASE);
@@ -1059,7 +1064,12 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
/* Check if slot is available */
if (likely(cur_bkt->key_idx[i] == EMPTY_SLOT)) {
cur_bkt->sig_current[i] = short_sig;
- cur_bkt->key_idx[i] = new_idx;
+ /* Store to signature should not leak after
+ * the store to key_idx
+ */
+ __atomic_store_n(&cur_bkt->key_idx[i],
+ new_idx,
+ __ATOMIC_RELEASE);
__hash_rw_writer_unlock(h);
return new_idx - 1;
}
@@ -1077,7 +1087,12 @@ __rte_hash_add_key_with_hash(const struct rte_hash *h, const void *key,
bkt_id = (uint32_t)((uintptr_t)ext_bkt_id) - 1;
/* Use the first location of the new bucket */
(h->buckets_ext[bkt_id]).sig_current[0] = short_sig;
- (h->buckets_ext[bkt_id]).key_idx[0] = new_idx;
+ /* Store to signature should not leak after
+ * the store to key_idx
+ */
+ __atomic_store_n(&(h->buckets_ext[bkt_id]).key_idx[0],
+ new_idx,
+ __ATOMIC_RELEASE);
/* Link the new bucket to sec bucket linked list */
last = rte_hash_get_last_bkt(sec_bkt);
last->next = &h->buckets_ext[bkt_id];
@@ -1371,7 +1386,8 @@ remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt, unsigned i)
* empty slot.
*/
static inline void
-__rte_hash_compact_ll(struct rte_hash_bucket *cur_bkt, int pos) {
+__rte_hash_compact_ll(const struct rte_hash *h,
+ struct rte_hash_bucket *cur_bkt, int pos) {
int i;
struct rte_hash_bucket *last_bkt;
@@ -1382,10 +1398,27 @@ __rte_hash_compact_ll(struct rte_hash_bucket *cur_bkt, int pos) {
for (i = RTE_HASH_BUCKET_ENTRIES - 1; i >= 0; i--) {
if (last_bkt->key_idx[i] != EMPTY_SLOT) {
- cur_bkt->key_idx[pos] = last_bkt->key_idx[i];
cur_bkt->sig_current[pos] = last_bkt->sig_current[i];
+ __atomic_store_n(&cur_bkt->key_idx[pos],
+ last_bkt->key_idx[i],
+ __ATOMIC_RELEASE);
+ if (h->readwrite_concur_lf_support) {
+ /* Inform the readers that the table has changed
+ * Since there is one writer, load acquire on
+ * tbl_chng_cnt is not required.
+ */
+ __atomic_store_n(h->tbl_chng_cnt,
+ *h->tbl_chng_cnt + 1,
+ __ATOMIC_RELEASE);
+ /* The store to sig_current should
+ * not move above the store to tbl_chng_cnt.
+ */
+ __atomic_thread_fence(__ATOMIC_RELEASE);
+ }
last_bkt->sig_current[i] = NULL_SIGNATURE;
- last_bkt->key_idx[i] = EMPTY_SLOT;
+ __atomic_store_n(&last_bkt->key_idx[i],
+ EMPTY_SLOT,
+ __ATOMIC_RELEASE);
return;
}
}
@@ -1454,7 +1487,7 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
/* look for key in primary bucket */
ret = search_and_remove(h, key, prim_bkt, short_sig, &pos);
if (ret != -1) {
- __rte_hash_compact_ll(prim_bkt, pos);
+ __rte_hash_compact_ll(h, prim_bkt, pos);
last_bkt = prim_bkt->next;
prev_bkt = prim_bkt;
goto return_bkt;
@@ -1466,7 +1499,7 @@ __rte_hash_del_key_with_hash(const struct rte_hash *h, const void *key,
FOR_EACH_BUCKET(cur_bkt, sec_bkt) {
ret = search_and_remove(h, key, cur_bkt, short_sig, &pos);
if (ret != -1) {
- __rte_hash_compact_ll(cur_bkt, pos);
+ __rte_hash_compact_ll(h, cur_bkt, pos);
last_bkt = sec_bkt->next;
prev_bkt = sec_bkt;
goto return_bkt;
@@ -1493,11 +1526,24 @@ return_bkt:
}
/* found empty bucket and recycle */
if (i == RTE_HASH_BUCKET_ENTRIES) {
- prev_bkt->next = last_bkt->next = NULL;
+ prev_bkt->next = NULL;
uint32_t index = last_bkt - h->buckets_ext + 1;
- rte_ring_sp_enqueue(h->free_ext_bkts, (void *)(uintptr_t)index);
+ /* Recycle the empty bkt if
+ * no_free_on_del is disabled.
+ */
+ if (h->no_free_on_del)
+ /* Store index of an empty ext bkt to be recycled
+ * on calling rte_hash_del_xxx APIs.
+ * When lock free read-write concurrency is enabled,
+ * an empty ext bkt cannot be put into free list
+ * immediately (as readers might be using it still).
+ * Hence freeing of the ext bkt is piggy-backed to
+ * freeing of the key index.
+ */
+ h->ext_bkt_to_free[ret] = index;
+ else
+ rte_ring_sp_enqueue(h->free_ext_bkts, (void *)(uintptr_t)index);
}
-
__hash_rw_writer_unlock(h);
return ret;
}
@@ -1550,6 +1596,14 @@ rte_hash_free_key_with_position(const struct rte_hash *h,
/* Out of bounds */
if (position >= total_entries)
return -EINVAL;
+ if (h->ext_table_support && h->readwrite_concur_lf_support) {
+ uint32_t index = h->ext_bkt_to_free[position];
+ if (index) {
+ /* Recycle empty ext bkt to free list. */
+ rte_ring_sp_enqueue(h->free_ext_bkts, (void *)(uintptr_t)index);
+ h->ext_bkt_to_free[position] = 0;
+ }
+ }
if (h->use_local_cache) {
lcore_id = rte_lcore_id();
@@ -1882,6 +1936,9 @@ __rte_hash_lookup_bulk_lf(const struct rte_hash *h, const void **keys,
rte_prefetch0(secondary_bkt[i]);
}
+ for (i = 0; i < num_keys; i++)
+ positions[i] = -ENOENT;
+
do {
/* Load the table change counter before the lookup
* starts. Acquire semantics will make sure that
@@ -1926,7 +1983,6 @@ __rte_hash_lookup_bulk_lf(const struct rte_hash *h, const void **keys,
/* Compare keys, first hits in primary first */
for (i = 0; i < num_keys; i++) {
- positions[i] = -ENOENT;
while (prim_hitmask[i]) {
uint32_t hit_index =
__builtin_ctzl(prim_hitmask[i])
@@ -1999,6 +2055,35 @@ next_key:
continue;
}
+ /* all found, do not need to go through ext bkt */
+ if (hits == ((1ULL << num_keys) - 1)) {
+ if (hit_mask != NULL)
+ *hit_mask = hits;
+ return;
+ }
+ /* need to check ext buckets for match */
+ if (h->ext_table_support) {
+ for (i = 0; i < num_keys; i++) {
+ if ((hits & (1ULL << i)) != 0)
+ continue;
+ next_bkt = secondary_bkt[i]->next;
+ FOR_EACH_BUCKET(cur_bkt, next_bkt) {
+ if (data != NULL)
+ ret = search_one_bucket_lf(h,
+ keys[i], sig[i],
+ &data[i], cur_bkt);
+ else
+ ret = search_one_bucket_lf(h,
+ keys[i], sig[i],
+ NULL, cur_bkt);
+ if (ret != -1) {
+ positions[i] = ret;
+ hits |= 1ULL << i;
+ break;
+ }
+ }
+ }
+ }
/* The loads of sig_current in compare_signatures
* should not move below the load from tbl_chng_cnt.
*/
@@ -2015,34 +2100,6 @@ next_key:
__ATOMIC_ACQUIRE);
} while (cnt_b != cnt_a);
- /* all found, do not need to go through ext bkt */
- if ((hits == ((1ULL << num_keys) - 1)) || !h->ext_table_support) {
- if (hit_mask != NULL)
- *hit_mask = hits;
- __hash_rw_reader_unlock(h);
- return;
- }
-
- /* need to check ext buckets for match */
- for (i = 0; i < num_keys; i++) {
- if ((hits & (1ULL << i)) != 0)
- continue;
- next_bkt = secondary_bkt[i]->next;
- FOR_EACH_BUCKET(cur_bkt, next_bkt) {
- if (data != NULL)
- ret = search_one_bucket_lf(h, keys[i],
- sig[i], &data[i], cur_bkt);
- else
- ret = search_one_bucket_lf(h, keys[i],
- sig[i], NULL, cur_bkt);
- if (ret != -1) {
- positions[i] = ret;
- hits |= 1ULL << i;
- break;
- }
- }
- }
-
if (hit_mask != NULL)
*hit_mask = hits;
}
diff --git a/lib/librte_hash/rte_cuckoo_hash.h b/lib/librte_hash/rte_cuckoo_hash.h
index 0548c97..fb19bb2 100644
--- a/lib/librte_hash/rte_cuckoo_hash.h
+++ b/lib/librte_hash/rte_cuckoo_hash.h
@@ -211,6 +211,13 @@ struct rte_hash {
rte_rwlock_t *readwrite_lock; /**< Read-write lock thread-safety. */
struct rte_hash_bucket *buckets_ext; /**< Extra buckets array */
struct rte_ring *free_ext_bkts; /**< Ring of indexes of free buckets */
+ /* Stores index of an empty ext bkt to be recycled on calling
+ * rte_hash_del_xxx APIs. When lock free read-write concurrency is
+ * enabled, an empty ext bkt cannot be put into free list immediately
+ * (as readers might be using it still). Hence freeing of the ext bkt
+ * is piggy-backed to freeing of the key index.
+ */
+ uint32_t *ext_bkt_to_free;
uint32_t *tbl_chng_cnt;
/**< Indicates if the hash table changed from last read. */
} __rte_cache_aligned;