src/vppinfra/bihash_template.c - fdio/vpp - Gitiles

 /*
  * Copyright (c) 2015 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 /** @cond DOCUMENTATION_IS_IN_BIHASH_DOC_H */

 static inline void *BV (alloc_aligned) (BVT (clib_bihash) * h, uword nbytes)
 {
   uword rv;

   /* Round to an even number of cache lines */
   nbytes += CLIB_CACHE_LINE_BYTES - 1;
   nbytes &= ~(CLIB_CACHE_LINE_BYTES - 1);

   rv = h->alloc_arena_next;
   h->alloc_arena_next += nbytes;

   if (rv >= (h->alloc_arena + h->alloc_arena_size))
     os_out_of_memory ();

   return (void *) rv;
 }


 void BV (clib_bihash_init)
   (BVT (clib_bihash) * h, char *name, u32 nbuckets, uword memory_size)
 {
   uword bucket_size;

   nbuckets = 1 << (max_log2 (nbuckets));

   h->name = (u8 *) name;
   h->nbuckets = nbuckets;
   h->log2_nbuckets = max_log2 (nbuckets);
   h->cache_hits = 0;
   h->cache_misses = 0;

   /*
    * Make sure the requested size is rational. The max table
    * size without playing the alignment card is 64 Gbytes.
    * If someone starts complaining that's not enough, we can shift
    * the offset by CLIB_LOG2_CACHE_LINE_BYTES...
    */
   ASSERT (memory_size < (1ULL << BIHASH_BUCKET_OFFSET_BITS));

   h->alloc_arena = (uword) clib_mem_vm_alloc (memory_size);
   h->alloc_arena_next = h->alloc_arena;
   h->alloc_arena_size = memory_size;

   bucket_size = nbuckets * sizeof (h->buckets[0]);
   h->buckets = BV (alloc_aligned) (h, bucket_size);

   h->alloc_lock = BV (alloc_aligned) (h, CLIB_CACHE_LINE_BYTES);
   h->alloc_lock[0] = 0;

   h->fmt_fn = NULL;
 }

 void BV (clib_bihash_set_kvp_format_fn) (BVT (clib_bihash) * h,
 					 format_function_t * fmt_fn)
 {
   h->fmt_fn = fmt_fn;
 }

 void BV (clib_bihash_free) (BVT (clib_bihash) * h)
 {
   vec_free (h->working_copies);
   vec_free (h->freelists);
   clib_mem_vm_free ((void *) (h->alloc_arena), h->alloc_arena_size);
   memset (h, 0, sizeof (*h));
 }

 static
 BVT (clib_bihash_value) *
 BV (value_alloc) (BVT (clib_bihash) * h, u32 log2_pages)
 {
   BVT (clib_bihash_value) * rv = 0;

   ASSERT (h->alloc_lock[0]);
   if (log2_pages >= vec_len (h->freelists) || h->freelists[log2_pages] == 0)
     {
       vec_validate_init_empty (h->freelists, log2_pages, 0);
       rv = BV (alloc_aligned) (h, (sizeof (*rv) * (1 << log2_pages)));
       goto initialize;
     }
   rv = h->freelists[log2_pages];
   h->freelists[log2_pages] = rv->next_free;

 initialize:
   ASSERT (rv);
   /*
    * Latest gcc complains that the length arg is zero
    * if we replace (1<<log2_pages) with vec_len(rv).
    * No clue.
    */
   memset (rv, 0xff, sizeof (*rv) * (1 << log2_pages));
   return rv;
 }

 static void
 BV (value_free) (BVT (clib_bihash) * h, BVT (clib_bihash_value) * v,
 		 u32 log2_pages)
 {
   ASSERT (h->alloc_lock[0]);

   ASSERT (vec_len (h->freelists) > log2_pages);

   if (CLIB_DEBUG > 0)
     memset (v, 0xFE, sizeof (*v) * (1 << log2_pages));

   v->next_free = h->freelists[log2_pages];
   h->freelists[log2_pages] = v;
 }

 static inline void
 BV (make_working_copy) (BVT (clib_bihash) * h, BVT (clib_bihash_bucket) * b)
 {
   BVT (clib_bihash_value) * v;
   BVT (clib_bihash_bucket) working_bucket __attribute__ ((aligned (8)));
   BVT (clib_bihash_value) * working_copy;
   u32 thread_index = os_get_thread_index ();
   int log2_working_copy_length;

   ASSERT (h->alloc_lock[0]);

   if (thread_index >= vec_len (h->working_copies))
     {
       vec_validate (h->working_copies, thread_index);
       vec_validate_init_empty (h->working_copy_lengths, thread_index, ~0);
     }

   /*
    * working_copies are per-cpu so that near-simultaneous
    * updates from multiple threads will not result in sporadic, spurious
    * lookup failures.
    */
   working_copy = h->working_copies[thread_index];
   log2_working_copy_length = h->working_copy_lengths[thread_index];

   h->saved_bucket.as_u64 = b->as_u64;

   if (b->log2_pages > log2_working_copy_length)
     {
       /*
        * It's not worth the bookkeeping to free working copies
        *   if (working_copy)
        *     clib_mem_free (working_copy);
        */
       working_copy = BV (alloc_aligned)
 	(h, sizeof (working_copy[0]) * (1 << b->log2_pages));
       h->working_copy_lengths[thread_index] = b->log2_pages;
       h->working_copies[thread_index] = working_copy;
     }

   v = BV (clib_bihash_get_value) (h, b->offset);

   clib_memcpy (working_copy, v, sizeof (*v) * (1 << b->log2_pages));
   working_bucket.as_u64 = b->as_u64;
   working_bucket.offset = BV (clib_bihash_get_offset) (h, working_copy);
   CLIB_MEMORY_BARRIER ();
   b->as_u64 = working_bucket.as_u64;
   h->working_copies[thread_index] = working_copy;
 }

 static
 BVT (clib_bihash_value) *
 BV (split_and_rehash)
   (BVT (clib_bihash) * h,
    BVT (clib_bihash_value) * old_values, u32 old_log2_pages,
    u32 new_log2_pages)
 {
   BVT (clib_bihash_value) * new_values, *new_v;
   int i, j, length_in_kvs;

   ASSERT (h->alloc_lock[0]);

   new_values = BV (value_alloc) (h, new_log2_pages);
   length_in_kvs = (1 << old_log2_pages) * BIHASH_KVP_PER_PAGE;

   for (i = 0; i < length_in_kvs; i++)
     {
       u64 new_hash;

       /* Entry not in use? Forget it */
       if (BV (clib_bihash_is_free) (&(old_values->kvp[i])))
 	continue;

       /* rehash the item onto its new home-page */
       new_hash = BV (clib_bihash_hash) (&(old_values->kvp[i]));
       new_hash >>= h->log2_nbuckets;
       new_hash &= (1 << new_log2_pages) - 1;
       new_v = &new_values[new_hash];

       /* Across the new home-page */
       for (j = 0; j < BIHASH_KVP_PER_PAGE; j++)
 	{
 	  /* Empty slot */
 	  if (BV (clib_bihash_is_free) (&(new_v->kvp[j])))
 	    {
 	      clib_memcpy (&(new_v->kvp[j]), &(old_values->kvp[i]),
 			   sizeof (new_v->kvp[j]));
 	      goto doublebreak;
 	    }
 	}
       /* Crap. Tell caller to try again */
       BV (value_free) (h, new_values, new_log2_pages);
       return 0;
     doublebreak:;
     }

   return new_values;
 }

 static
 BVT (clib_bihash_value) *
 BV (split_and_rehash_linear)
   (BVT (clib_bihash) * h,
    BVT (clib_bihash_value) * old_values, u32 old_log2_pages,
    u32 new_log2_pages)
 {
   BVT (clib_bihash_value) * new_values;
   int i, j, new_length, old_length;

   ASSERT (h->alloc_lock[0]);

   new_values = BV (value_alloc) (h, new_log2_pages);
   new_length = (1 << new_log2_pages) * BIHASH_KVP_PER_PAGE;
   old_length = (1 << old_log2_pages) * BIHASH_KVP_PER_PAGE;

   j = 0;
   /* Across the old value array */
   for (i = 0; i < old_length; i++)
     {
       /* Find a free slot in the new linear scan bucket */
       for (; j < new_length; j++)
 	{
 	  /* Old value not in use? Forget it. */
 	  if (BV (clib_bihash_is_free) (&(old_values->kvp[i])))
 	    goto doublebreak;

 	  /* New value should never be in use */
 	  if (BV (clib_bihash_is_free) (&(new_values->kvp[j])))
 	    {
 	      /* Copy the old value and move along */
 	      clib_memcpy (&(new_values->kvp[j]), &(old_values->kvp[i]),
 			   sizeof (new_values->kvp[j]));
 	      j++;
 	      goto doublebreak;
 	    }
 	}
       /* This should never happen... */
       clib_warning ("BUG: linear rehash failed!");
       BV (value_free) (h, new_values, new_log2_pages);
       return 0;

     doublebreak:;
     }
   return new_values;
 }

 int BV (clib_bihash_add_del)
   (BVT (clib_bihash) * h, BVT (clib_bihash_kv) * add_v, int is_add)
 {
   u32 bucket_index;
   BVT (clib_bihash_bucket) * b, tmp_b;
   BVT (clib_bihash_value) * v, *new_v, *save_new_v, *working_copy;
   int i, limit;
   u64 hash, new_hash;
   u32 new_log2_pages, old_log2_pages;
   u32 thread_index = os_get_thread_index ();
   int mark_bucket_linear;
   int resplit_once;

   hash = BV (clib_bihash_hash) (add_v);

   bucket_index = hash & (h->nbuckets - 1);
   b = &h->buckets[bucket_index];

   hash >>= h->log2_nbuckets;

   BV (clib_bihash_lock_bucket) (b);

   /* First elt in the bucket? */
   if (BV (clib_bihash_bucket_is_empty) (b))
     {
       if (is_add == 0)
 	{
 	  BV (clib_bihash_unlock_bucket) (b);
 	  return (-1);
 	}

       BV (clib_bihash_alloc_lock) (h);
       v = BV (value_alloc) (h, 0);
       BV (clib_bihash_alloc_unlock) (h);

       *v->kvp = *add_v;
       tmp_b.as_u64 = 0;		/* clears bucket lock */
       tmp_b.offset = BV (clib_bihash_get_offset) (h, v);
       tmp_b.refcnt = 1;
       CLIB_MEMORY_BARRIER ();

       b->as_u64 = tmp_b.as_u64;
       BV (clib_bihash_unlock_bucket) (b);
       return (0);
     }

   /* WARNING: we're still looking at the live copy... */
   limit = BIHASH_KVP_PER_PAGE;
   v = BV (clib_bihash_get_value) (h, b->offset);

   v += (b->linear_search == 0) ? hash & ((1 << b->log2_pages) - 1) : 0;
   if (b->linear_search)
     limit <<= b->log2_pages;

   if (is_add)
     {
       /*
        * Because reader threads are looking at live data,
        * we have to be extra careful. Readers do NOT hold the
        * bucket lock. We need to be SLOWER than a search, past the
        * point where readers CHECK the bucket lock.
        */

       /*
        * For obvious (in hindsight) reasons, see if we're supposed to
        * replace an existing key, then look for an empty slot.
        */
       for (i = 0; i < limit; i++)
 	{
 	  if (!memcmp (&(v->kvp[i]), &add_v->key, sizeof (add_v->key)))
 	    {
 	      CLIB_MEMORY_BARRIER ();	/* Add a delay */
 	      clib_memcpy (&(v->kvp[i]), add_v, sizeof (*add_v));
 	      BV (clib_bihash_unlock_bucket) (b);
 	      return (0);
 	    }
 	}
       /*
        * Look for an empty slot. If found, use it
        */
       for (i = 0; i < limit; i++)
 	{
 	  if (BV (clib_bihash_is_free) (&(v->kvp[i])))
 	    {
 	      /*
 	       * Copy the value first, so that if a reader manages
 	       * to match the new key, the value will be right...
 	       */
 	      clib_memcpy (&(v->kvp[i].value),
 			   &add_v->value, sizeof (add_v->value));
 	      CLIB_MEMORY_BARRIER ();	/* Make sure the value has settled */
 	      clib_memcpy (&(v->kvp[i]), &add_v->key, sizeof (add_v->key));
 	      b->refcnt++;
 	      BV (clib_bihash_unlock_bucket) (b);
 	      return (0);
 	    }
 	}
       /* Out of space in this bucket, split the bucket... */
     }
   else				/* delete case */
     {
       for (i = 0; i < limit; i++)
 	{
 	  /* Found the key? Kill it... */
 	  if (!memcmp (&(v->kvp[i]), &add_v->key, sizeof (add_v->key)))
 	    {
 	      memset (&(v->kvp[i]), 0xff, sizeof (*(add_v)));
 	      /* Is the bucket empty? */
 	      if (PREDICT_TRUE (b->refcnt > 1))
 		{
 		  b->refcnt--;
 		  BV (clib_bihash_unlock_bucket) (b);
 		  return (0);
 		}
 	      else		/* yes, free it */
 		{
 		  /* Save old bucket value, need log2_pages to free it */
 		  tmp_b.as_u64 = b->as_u64;
 		  CLIB_MEMORY_BARRIER ();

 		  /* Kill and unlock the bucket */
 		  b->as_u64 = 0;

 		  /* And free the backing storage */
 		  BV (clib_bihash_alloc_lock) (h);
 		  /* Note: v currently points into the middle of the bucket */
 		  v = BV (clib_bihash_get_value) (h, tmp_b.offset);
 		  BV (value_free) (h, v, tmp_b.log2_pages);
 		  BV (clib_bihash_alloc_unlock) (h);
 		  return (0);
 		}
 	    }
 	}
       /* Not found... */
       BV (clib_bihash_unlock_bucket) (b);
       return (-3);
     }

   /* Move readers to a (locked) temp copy of the bucket */
   BV (clib_bihash_alloc_lock) (h);
   BV (make_working_copy) (h, b);

   v = BV (clib_bihash_get_value) (h, h->saved_bucket.offset);

   old_log2_pages = h->saved_bucket.log2_pages;
   new_log2_pages = old_log2_pages + 1;
   mark_bucket_linear = 0;

   working_copy = h->working_copies[thread_index];
   resplit_once = 0;

   new_v = BV (split_and_rehash) (h, working_copy, old_log2_pages,
 				 new_log2_pages);
   if (new_v == 0)
     {
     try_resplit:
       resplit_once = 1;
       new_log2_pages++;
       /* Try re-splitting. If that fails, fall back to linear search */
       new_v = BV (split_and_rehash) (h, working_copy, old_log2_pages,
 				     new_log2_pages);
       if (new_v == 0)
 	{
 	mark_linear:
 	  new_log2_pages--;
 	  /* pinned collisions, use linear search */
 	  new_v =
 	    BV (split_and_rehash_linear) (h, working_copy, old_log2_pages,
 					  new_log2_pages);
 	  mark_bucket_linear = 1;
 	}
     }

   /* Try to add the new entry */
   save_new_v = new_v;
   new_hash = BV (clib_bihash_hash) (add_v);
   limit = BIHASH_KVP_PER_PAGE;
   if (mark_bucket_linear)
     limit <<= new_log2_pages;
   new_hash >>= h->log2_nbuckets;
   new_hash &= (1 << new_log2_pages) - 1;
   new_v += mark_bucket_linear ? 0 : new_hash;

   for (i = 0; i < limit; i++)
     {
       if (BV (clib_bihash_is_free) (&(new_v->kvp[i])))
 	{
 	  clib_memcpy (&(new_v->kvp[i]), add_v, sizeof (*add_v));
 	  goto expand_ok;
 	}
     }

   /* Crap. Try again */
   BV (value_free) (h, save_new_v, new_log2_pages);
   /*
    * If we've already doubled the size of the bucket once,
    * fall back to linear search now.
    */
   if (resplit_once)
     goto mark_linear;
   else
     goto try_resplit;

 expand_ok:
   tmp_b.log2_pages = new_log2_pages;
   tmp_b.offset = BV (clib_bihash_get_offset) (h, save_new_v);
   tmp_b.linear_search = mark_bucket_linear;
   tmp_b.refcnt = h->saved_bucket.refcnt + 1;
   tmp_b.lock = 0;
   CLIB_MEMORY_BARRIER ();
   b->as_u64 = tmp_b.as_u64;
   BV (clib_bihash_alloc_unlock) (h);
   return (0);
 }

 int BV (clib_bihash_search)
   (BVT (clib_bihash) * h,
    BVT (clib_bihash_kv) * search_key, BVT (clib_bihash_kv) * valuep)
 {
   u64 hash;
   u32 bucket_index;
   BVT (clib_bihash_value) * v;
   BVT (clib_bihash_bucket) * b;
   int i, limit;

   ASSERT (valuep);

   hash = BV (clib_bihash_hash) (search_key);

   bucket_index = hash & (h->nbuckets - 1);
   b = &h->buckets[bucket_index];

   if (BV (clib_bihash_bucket_is_empty) (b))
     return -1;

   if (PREDICT_FALSE (b->lock))
     {
       volatile BVT (clib_bihash_bucket) * bv = b;
       while (bv->lock)
 	CLIB_PAUSE ();
     }

   hash >>= h->log2_nbuckets;

   v = BV (clib_bihash_get_value) (h, b->offset);
   limit = BIHASH_KVP_PER_PAGE;
   v += (b->linear_search == 0) ? hash & ((1 << b->log2_pages) - 1) : 0;
   if (PREDICT_FALSE (b->linear_search))
     limit <<= b->log2_pages;

   for (i = 0; i < limit; i++)
     {
       if (BV (clib_bihash_key_compare) (v->kvp[i].key, search_key->key))
 	{
 	  *valuep = v->kvp[i];
 	  return 0;
 	}
     }
   return -1;
 }

 u8 *BV (format_bihash) (u8 * s, va_list * args)
 {
   BVT (clib_bihash) * h = va_arg (*args, BVT (clib_bihash) *);
   int verbose = va_arg (*args, int);
   BVT (clib_bihash_bucket) * b;
   BVT (clib_bihash_value) * v;
   int i, j, k;
   u64 active_elements = 0;
   u64 active_buckets = 0;
   u64 linear_buckets = 0;
   u64 used_bytes;

   s = format (s, "Hash table %s\n", h->name ? h->name : (u8 *) "(unnamed)");

   for (i = 0; i < h->nbuckets; i++)
     {
       b = &h->buckets[i];
       if (BV (clib_bihash_bucket_is_empty) (b))
 	{
 	  if (verbose > 1)
 	    s = format (s, "[%d]: empty\n", i);
 	  continue;
 	}

       active_buckets++;

       if (b->linear_search)
 	linear_buckets++;

       if (verbose)
 	{
 	  s = format (s, "[%d]: heap offset %d, len %d, linear %d\n", i,
 		      b->offset, (1 << b->log2_pages), b->linear_search);
 	}

       v = BV (clib_bihash_get_value) (h, b->offset);
       for (j = 0; j < (1 << b->log2_pages); j++)
 	{
 	  for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
 	    {
 	      if (BV (clib_bihash_is_free) (&v->kvp[k]))
 		{
 		  if (verbose > 1)
 		    s = format (s, "    %d: empty\n",
 				j * BIHASH_KVP_PER_PAGE + k);
 		  continue;
 		}
 	      if (verbose)
 		{
 		  if (h->fmt_fn)
 		    {
 		      s = format (s, "    %d: %U\n",
 				  j * BIHASH_KVP_PER_PAGE + k,
 				  h->fmt_fn, &(v->kvp[k]));
 		    }
 		  else
 		    {
 		      s = format (s, "    %d: %U\n",
 				  j * BIHASH_KVP_PER_PAGE + k,
 				  BV (format_bihash_kvp), &(v->kvp[k]));
 		    }
 		}
 	      active_elements++;
 	    }
 	  v++;
 	}
     }

   s = format (s, "    %lld active elements %lld active buckets\n",
 	      active_elements, active_buckets);
   s = format (s, "    %d free lists\n", vec_len (h->freelists));

   for (i = 0; i < vec_len (h->freelists); i++)
     {
       u32 nfree = 0;
       BVT (clib_bihash_value) * free_elt;

       free_elt = h->freelists[i];
       while (free_elt)
 	{
 	  nfree++;
 	  free_elt = free_elt->next_free;
 	}

       s = format (s, "       [len %d] %u free elts\n", 1 << i, nfree);
     }

   s = format (s, "    %lld linear search buckets\n", linear_buckets);
   s = format (s, "    %lld cache hits, %lld cache misses\n",
 	      h->cache_hits, h->cache_misses);
   used_bytes = h->alloc_arena_next - h->alloc_arena;
   s = format (s,
 	      "    arena: base %llx, next %llx\n"
 	      "           used %lld b (%lld Mbytes) of %lld b (%lld Mbytes)\n",
 	      h->alloc_arena, h->alloc_arena_next,
 	      used_bytes, used_bytes >> 20,
 	      h->alloc_arena_size, h->alloc_arena_size >> 20);
   return s;
 }

 void BV (clib_bihash_foreach_key_value_pair)
   (BVT (clib_bihash) * h, void *callback, void *arg)
 {
   int i, j, k;
   BVT (clib_bihash_bucket) * b;
   BVT (clib_bihash_value) * v;
   void (*fp) (BVT (clib_bihash_kv) *, void *) = callback;

   for (i = 0; i < h->nbuckets; i++)
     {
       b = &h->buckets[i];
       if (BV (clib_bihash_bucket_is_empty) (b))
 	continue;

       v = BV (clib_bihash_get_value) (h, b->offset);
       for (j = 0; j < (1 << b->log2_pages); j++)
 	{
 	  for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
 	    {
 	      if (BV (clib_bihash_is_free) (&v->kvp[k]))
 		continue;

 	      (*fp) (&v->kvp[k], arg);
 	      /*
 	       * In case the callback deletes the last entry in the bucket...
 	       */
 	      if (BV (clib_bihash_bucket_is_empty) (b))
 		goto doublebreak;
 	    }
 	  v++;
 	}
     doublebreak:
       ;
     }
 }

 /** @endcond */

 /*
  * fd.io coding-style-patch-verification: ON
  *
  * Local Variables:
  * eval: (c-set-style "gnu")
  * End:
  */
	/*
	* Copyright (c) 2015 Cisco and/or its affiliates.
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at:
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	/** @cond DOCUMENTATION_IS_IN_BIHASH_DOC_H */

	static inline void BV (alloc_aligned) (BVT (clib_bihash) h, uword nbytes)
	{
	uword rv;

	/* Round to an even number of cache lines */
	nbytes += CLIB_CACHE_LINE_BYTES - 1;
	nbytes &= ~(CLIB_CACHE_LINE_BYTES - 1);

	rv = h->alloc_arena_next;
	h->alloc_arena_next += nbytes;

	if (rv >= (h->alloc_arena + h->alloc_arena_size))
	os_out_of_memory ();

	return (void *) rv;
	}


	void BV (clib_bihash_init)
	(BVT (clib_bihash) * h, char *name, u32 nbuckets, uword memory_size)
	{
	uword bucket_size;

	nbuckets = 1 << (max_log2 (nbuckets));

	h->name = (u8 *) name;
	h->nbuckets = nbuckets;
	h->log2_nbuckets = max_log2 (nbuckets);
	h->cache_hits = 0;
	h->cache_misses = 0;

	/*
	* Make sure the requested size is rational. The max table
	* size without playing the alignment card is 64 Gbytes.
	* If someone starts complaining that's not enough, we can shift
	* the offset by CLIB_LOG2_CACHE_LINE_BYTES...
	*/
	ASSERT (memory_size < (1ULL << BIHASH_BUCKET_OFFSET_BITS));

	h->alloc_arena = (uword) clib_mem_vm_alloc (memory_size);
	h->alloc_arena_next = h->alloc_arena;
	h->alloc_arena_size = memory_size;

	bucket_size = nbuckets * sizeof (h->buckets[0]);
	h->buckets = BV (alloc_aligned) (h, bucket_size);

	h->alloc_lock = BV (alloc_aligned) (h, CLIB_CACHE_LINE_BYTES);
	h->alloc_lock[0] = 0;

	h->fmt_fn = NULL;
	}

	void BV (clib_bihash_set_kvp_format_fn) (BVT (clib_bihash) * h,
	format_function_t * fmt_fn)
	{
	h->fmt_fn = fmt_fn;
	}

	void BV (clib_bihash_free) (BVT (clib_bihash) * h)
	{
	vec_free (h->working_copies);
	vec_free (h->freelists);
	clib_mem_vm_free ((void *) (h->alloc_arena), h->alloc_arena_size);
	memset (h, 0, sizeof (*h));
	}

	static
	BVT (clib_bihash_value) *
	BV (value_alloc) (BVT (clib_bihash) * h, u32 log2_pages)
	{
	BVT (clib_bihash_value) * rv = 0;

	ASSERT (h->alloc_lock[0]);
	if (log2_pages >= vec_len (h->freelists) \|\| h->freelists[log2_pages] == 0)
	{
	vec_validate_init_empty (h->freelists, log2_pages, 0);
	rv = BV (alloc_aligned) (h, (sizeof (rv) (1 << log2_pages)));
	goto initialize;
	}
	rv = h->freelists[log2_pages];
	h->freelists[log2_pages] = rv->next_free;

	initialize:
	ASSERT (rv);
	/*
	* Latest gcc complains that the length arg is zero
	* if we replace (1<<log2_pages) with vec_len(rv).
	* No clue.
	*/
	memset (rv, 0xff, sizeof (rv) (1 << log2_pages));
	return rv;
	}

	static void
	BV (value_free) (BVT (clib_bihash) * h, BVT (clib_bihash_value) * v,
	u32 log2_pages)
	{
	ASSERT (h->alloc_lock[0]);

	ASSERT (vec_len (h->freelists) > log2_pages);

	if (CLIB_DEBUG > 0)
	memset (v, 0xFE, sizeof (v) (1 << log2_pages));

	v->next_free = h->freelists[log2_pages];
	h->freelists[log2_pages] = v;
	}

	static inline void
	BV (make_working_copy) (BVT (clib_bihash) * h, BVT (clib_bihash_bucket) * b)
	{
	BVT (clib_bihash_value) * v;
	BVT (clib_bihash_bucket) working_bucket __attribute__ ((aligned (8)));
	BVT (clib_bihash_value) * working_copy;
	u32 thread_index = os_get_thread_index ();
	int log2_working_copy_length;

	ASSERT (h->alloc_lock[0]);

	if (thread_index >= vec_len (h->working_copies))
	{
	vec_validate (h->working_copies, thread_index);
	vec_validate_init_empty (h->working_copy_lengths, thread_index, ~0);
	}

	/*
	* working_copies are per-cpu so that near-simultaneous
	* updates from multiple threads will not result in sporadic, spurious
	* lookup failures.
	*/
	working_copy = h->working_copies[thread_index];
	log2_working_copy_length = h->working_copy_lengths[thread_index];

	h->saved_bucket.as_u64 = b->as_u64;

	if (b->log2_pages > log2_working_copy_length)
	{
	/*
	* It's not worth the bookkeeping to free working copies
	* if (working_copy)
	* clib_mem_free (working_copy);
	*/
	working_copy = BV (alloc_aligned)
	(h, sizeof (working_copy[0]) * (1 << b->log2_pages));
	h->working_copy_lengths[thread_index] = b->log2_pages;
	h->working_copies[thread_index] = working_copy;
	}

	v = BV (clib_bihash_get_value) (h, b->offset);

	clib_memcpy (working_copy, v, sizeof (v) (1 << b->log2_pages));
	working_bucket.as_u64 = b->as_u64;
	working_bucket.offset = BV (clib_bihash_get_offset) (h, working_copy);
	CLIB_MEMORY_BARRIER ();
	b->as_u64 = working_bucket.as_u64;
	h->working_copies[thread_index] = working_copy;
	}

	static
	BVT (clib_bihash_value) *
	BV (split_and_rehash)
	(BVT (clib_bihash) * h,
	BVT (clib_bihash_value) * old_values, u32 old_log2_pages,
	u32 new_log2_pages)
	{
	BVT (clib_bihash_value) * new_values, *new_v;
	int i, j, length_in_kvs;

	ASSERT (h->alloc_lock[0]);

	new_values = BV (value_alloc) (h, new_log2_pages);
	length_in_kvs = (1 << old_log2_pages) * BIHASH_KVP_PER_PAGE;

	for (i = 0; i < length_in_kvs; i++)
	{
	u64 new_hash;

	/* Entry not in use? Forget it */
	if (BV (clib_bihash_is_free) (&(old_values->kvp[i])))
	continue;

	/* rehash the item onto its new home-page */
	new_hash = BV (clib_bihash_hash) (&(old_values->kvp[i]));
	new_hash >>= h->log2_nbuckets;
	new_hash &= (1 << new_log2_pages) - 1;
	new_v = &new_values[new_hash];

	/* Across the new home-page */
	for (j = 0; j < BIHASH_KVP_PER_PAGE; j++)
	{
	/* Empty slot */
	if (BV (clib_bihash_is_free) (&(new_v->kvp[j])))
	{
	clib_memcpy (&(new_v->kvp[j]), &(old_values->kvp[i]),
	sizeof (new_v->kvp[j]));
	goto doublebreak;
	}
	}
	/* Crap. Tell caller to try again */
	BV (value_free) (h, new_values, new_log2_pages);
	return 0;
	doublebreak:;
	}

	return new_values;
	}

	static
	BVT (clib_bihash_value) *
	BV (split_and_rehash_linear)
	(BVT (clib_bihash) * h,
	BVT (clib_bihash_value) * old_values, u32 old_log2_pages,
	u32 new_log2_pages)
	{
	BVT (clib_bihash_value) * new_values;
	int i, j, new_length, old_length;

	ASSERT (h->alloc_lock[0]);

	new_values = BV (value_alloc) (h, new_log2_pages);
	new_length = (1 << new_log2_pages) * BIHASH_KVP_PER_PAGE;
	old_length = (1 << old_log2_pages) * BIHASH_KVP_PER_PAGE;

	j = 0;
	/* Across the old value array */
	for (i = 0; i < old_length; i++)
	{
	/* Find a free slot in the new linear scan bucket */
	for (; j < new_length; j++)
	{
	/* Old value not in use? Forget it. */
	if (BV (clib_bihash_is_free) (&(old_values->kvp[i])))
	goto doublebreak;

	/* New value should never be in use */
	if (BV (clib_bihash_is_free) (&(new_values->kvp[j])))
	{
	/* Copy the old value and move along */
	clib_memcpy (&(new_values->kvp[j]), &(old_values->kvp[i]),
	sizeof (new_values->kvp[j]));
	j++;
	goto doublebreak;
	}
	}
	/* This should never happen... */
	clib_warning ("BUG: linear rehash failed!");
	BV (value_free) (h, new_values, new_log2_pages);
	return 0;

	doublebreak:;
	}
	return new_values;
	}

	int BV (clib_bihash_add_del)
	(BVT (clib_bihash) * h, BVT (clib_bihash_kv) * add_v, int is_add)
	{
	u32 bucket_index;
	BVT (clib_bihash_bucket) * b, tmp_b;
	BVT (clib_bihash_value) * v, new_v, save_new_v, *working_copy;
	int i, limit;
	u64 hash, new_hash;
	u32 new_log2_pages, old_log2_pages;
	u32 thread_index = os_get_thread_index ();
	int mark_bucket_linear;
	int resplit_once;

	hash = BV (clib_bihash_hash) (add_v);

	bucket_index = hash & (h->nbuckets - 1);
	b = &h->buckets[bucket_index];

	hash >>= h->log2_nbuckets;

	BV (clib_bihash_lock_bucket) (b);

	/* First elt in the bucket? */
	if (BV (clib_bihash_bucket_is_empty) (b))
	{
	if (is_add == 0)
	{
	BV (clib_bihash_unlock_bucket) (b);
	return (-1);
	}

	BV (clib_bihash_alloc_lock) (h);
	v = BV (value_alloc) (h, 0);
	BV (clib_bihash_alloc_unlock) (h);

	v->kvp = add_v;
	tmp_b.as_u64 = 0; /* clears bucket lock */
	tmp_b.offset = BV (clib_bihash_get_offset) (h, v);
	tmp_b.refcnt = 1;
	CLIB_MEMORY_BARRIER ();

	b->as_u64 = tmp_b.as_u64;
	BV (clib_bihash_unlock_bucket) (b);
	return (0);
	}

	/* WARNING: we're still looking at the live copy... */
	limit = BIHASH_KVP_PER_PAGE;
	v = BV (clib_bihash_get_value) (h, b->offset);

	v += (b->linear_search == 0) ? hash & ((1 << b->log2_pages) - 1) : 0;
	if (b->linear_search)
	limit <<= b->log2_pages;

	if (is_add)
	{
	/*
	* Because reader threads are looking at live data,
	* we have to be extra careful. Readers do NOT hold the
	* bucket lock. We need to be SLOWER than a search, past the
	* point where readers CHECK the bucket lock.
	*/

	/*
	* For obvious (in hindsight) reasons, see if we're supposed to
	* replace an existing key, then look for an empty slot.
	*/
	for (i = 0; i < limit; i++)
	{
	if (!memcmp (&(v->kvp[i]), &add_v->key, sizeof (add_v->key)))
	{
	CLIB_MEMORY_BARRIER (); /* Add a delay */
	clib_memcpy (&(v->kvp[i]), add_v, sizeof (*add_v));
	BV (clib_bihash_unlock_bucket) (b);
	return (0);
	}
	}
	/*
	* Look for an empty slot. If found, use it
	*/
	for (i = 0; i < limit; i++)
	{
	if (BV (clib_bihash_is_free) (&(v->kvp[i])))
	{
	/*
	* Copy the value first, so that if a reader manages
	* to match the new key, the value will be right...
	*/
	clib_memcpy (&(v->kvp[i].value),
	&add_v->value, sizeof (add_v->value));
	CLIB_MEMORY_BARRIER (); /* Make sure the value has settled */
	clib_memcpy (&(v->kvp[i]), &add_v->key, sizeof (add_v->key));
	b->refcnt++;
	BV (clib_bihash_unlock_bucket) (b);
	return (0);
	}
	}
	/* Out of space in this bucket, split the bucket... */
	}
	else /* delete case */
	{
	for (i = 0; i < limit; i++)
	{
	/* Found the key? Kill it... */
	if (!memcmp (&(v->kvp[i]), &add_v->key, sizeof (add_v->key)))
	{
	memset (&(v->kvp[i]), 0xff, sizeof (*(add_v)));
	/* Is the bucket empty? */
	if (PREDICT_TRUE (b->refcnt > 1))
	{
	b->refcnt--;
	BV (clib_bihash_unlock_bucket) (b);
	return (0);
	}
	else /* yes, free it */
	{
	/* Save old bucket value, need log2_pages to free it */
	tmp_b.as_u64 = b->as_u64;
	CLIB_MEMORY_BARRIER ();

	/* Kill and unlock the bucket */
	b->as_u64 = 0;

	/* And free the backing storage */
	BV (clib_bihash_alloc_lock) (h);
	/* Note: v currently points into the middle of the bucket */
	v = BV (clib_bihash_get_value) (h, tmp_b.offset);
	BV (value_free) (h, v, tmp_b.log2_pages);
	BV (clib_bihash_alloc_unlock) (h);
	return (0);
	}
	}
	}
	/* Not found... */
	BV (clib_bihash_unlock_bucket) (b);
	return (-3);
	}

	/* Move readers to a (locked) temp copy of the bucket */
	BV (clib_bihash_alloc_lock) (h);
	BV (make_working_copy) (h, b);

	v = BV (clib_bihash_get_value) (h, h->saved_bucket.offset);

	old_log2_pages = h->saved_bucket.log2_pages;
	new_log2_pages = old_log2_pages + 1;
	mark_bucket_linear = 0;

	working_copy = h->working_copies[thread_index];
	resplit_once = 0;

	new_v = BV (split_and_rehash) (h, working_copy, old_log2_pages,
	new_log2_pages);
	if (new_v == 0)
	{
	try_resplit:
	resplit_once = 1;
	new_log2_pages++;
	/* Try re-splitting. If that fails, fall back to linear search */
	new_v = BV (split_and_rehash) (h, working_copy, old_log2_pages,
	new_log2_pages);
	if (new_v == 0)
	{
	mark_linear:
	new_log2_pages--;
	/* pinned collisions, use linear search */
	new_v =
	BV (split_and_rehash_linear) (h, working_copy, old_log2_pages,
	new_log2_pages);
	mark_bucket_linear = 1;
	}
	}

	/* Try to add the new entry */
	save_new_v = new_v;
	new_hash = BV (clib_bihash_hash) (add_v);
	limit = BIHASH_KVP_PER_PAGE;
	if (mark_bucket_linear)
	limit <<= new_log2_pages;
	new_hash >>= h->log2_nbuckets;
	new_hash &= (1 << new_log2_pages) - 1;
	new_v += mark_bucket_linear ? 0 : new_hash;

	for (i = 0; i < limit; i++)
	{
	if (BV (clib_bihash_is_free) (&(new_v->kvp[i])))
	{
	clib_memcpy (&(new_v->kvp[i]), add_v, sizeof (*add_v));
	goto expand_ok;
	}
	}

	/* Crap. Try again */
	BV (value_free) (h, save_new_v, new_log2_pages);
	/*
	* If we've already doubled the size of the bucket once,
	* fall back to linear search now.
	*/
	if (resplit_once)
	goto mark_linear;
	else
	goto try_resplit;

	expand_ok:
	tmp_b.log2_pages = new_log2_pages;
	tmp_b.offset = BV (clib_bihash_get_offset) (h, save_new_v);
	tmp_b.linear_search = mark_bucket_linear;
	tmp_b.refcnt = h->saved_bucket.refcnt + 1;
	tmp_b.lock = 0;
	CLIB_MEMORY_BARRIER ();
	b->as_u64 = tmp_b.as_u64;
	BV (clib_bihash_alloc_unlock) (h);
	return (0);
	}

	int BV (clib_bihash_search)
	(BVT (clib_bihash) * h,
	BVT (clib_bihash_kv) * search_key, BVT (clib_bihash_kv) * valuep)
	{
	u64 hash;
	u32 bucket_index;
	BVT (clib_bihash_value) * v;
	BVT (clib_bihash_bucket) * b;
	int i, limit;

	ASSERT (valuep);

	hash = BV (clib_bihash_hash) (search_key);

	bucket_index = hash & (h->nbuckets - 1);
	b = &h->buckets[bucket_index];

	if (BV (clib_bihash_bucket_is_empty) (b))
	return -1;

	if (PREDICT_FALSE (b->lock))
	{
	volatile BVT (clib_bihash_bucket) * bv = b;
	while (bv->lock)
	CLIB_PAUSE ();
	}

	hash >>= h->log2_nbuckets;

	v = BV (clib_bihash_get_value) (h, b->offset);
	limit = BIHASH_KVP_PER_PAGE;
	v += (b->linear_search == 0) ? hash & ((1 << b->log2_pages) - 1) : 0;
	if (PREDICT_FALSE (b->linear_search))
	limit <<= b->log2_pages;

	for (i = 0; i < limit; i++)
	{
	if (BV (clib_bihash_key_compare) (v->kvp[i].key, search_key->key))
	{
	*valuep = v->kvp[i];
	return 0;
	}
	}
	return -1;
	}

	u8 BV (format_bihash) (u8 s, va_list * args)
	{
	BVT (clib_bihash) * h = va_arg (args, BVT (clib_bihash) );
	int verbose = va_arg (*args, int);
	BVT (clib_bihash_bucket) * b;
	BVT (clib_bihash_value) * v;
	int i, j, k;
	u64 active_elements = 0;
	u64 active_buckets = 0;
	u64 linear_buckets = 0;
	u64 used_bytes;

	s = format (s, "Hash table %s\n", h->name ? h->name : (u8 *) "(unnamed)");

	for (i = 0; i < h->nbuckets; i++)
	{
	b = &h->buckets[i];
	if (BV (clib_bihash_bucket_is_empty) (b))
	{
	if (verbose > 1)
	s = format (s, "[%d]: empty\n", i);
	continue;
	}

	active_buckets++;

	if (b->linear_search)
	linear_buckets++;

	if (verbose)
	{
	s = format (s, "[%d]: heap offset %d, len %d, linear %d\n", i,
	b->offset, (1 << b->log2_pages), b->linear_search);
	}

	v = BV (clib_bihash_get_value) (h, b->offset);
	for (j = 0; j < (1 << b->log2_pages); j++)
	{
	for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
	{
	if (BV (clib_bihash_is_free) (&v->kvp[k]))
	{
	if (verbose > 1)
	s = format (s, " %d: empty\n",
	j * BIHASH_KVP_PER_PAGE + k);
	continue;
	}
	if (verbose)
	{
	if (h->fmt_fn)
	{
	s = format (s, " %d: %U\n",
	j * BIHASH_KVP_PER_PAGE + k,
	h->fmt_fn, &(v->kvp[k]));
	}
	else
	{
	s = format (s, " %d: %U\n",
	j * BIHASH_KVP_PER_PAGE + k,
	BV (format_bihash_kvp), &(v->kvp[k]));
	}
	}
	active_elements++;
	}
	v++;
	}
	}

	s = format (s, " %lld active elements %lld active buckets\n",
	active_elements, active_buckets);
	s = format (s, " %d free lists\n", vec_len (h->freelists));

	for (i = 0; i < vec_len (h->freelists); i++)
	{
	u32 nfree = 0;
	BVT (clib_bihash_value) * free_elt;

	free_elt = h->freelists[i];
	while (free_elt)
	{
	nfree++;
	free_elt = free_elt->next_free;
	}

	s = format (s, " [len %d] %u free elts\n", 1 << i, nfree);
	}

	s = format (s, " %lld linear search buckets\n", linear_buckets);
	s = format (s, " %lld cache hits, %lld cache misses\n",
	h->cache_hits, h->cache_misses);
	used_bytes = h->alloc_arena_next - h->alloc_arena;
	s = format (s,
	" arena: base %llx, next %llx\n"
	" used %lld b (%lld Mbytes) of %lld b (%lld Mbytes)\n",
	h->alloc_arena, h->alloc_arena_next,
	used_bytes, used_bytes >> 20,
	h->alloc_arena_size, h->alloc_arena_size >> 20);
	return s;
	}

	void BV (clib_bihash_foreach_key_value_pair)
	(BVT (clib_bihash) * h, void callback, void arg)
	{
	int i, j, k;
	BVT (clib_bihash_bucket) * b;
	BVT (clib_bihash_value) * v;
	void (fp) (BVT (clib_bihash_kv) , void *) = callback;

	for (i = 0; i < h->nbuckets; i++)
	{
	b = &h->buckets[i];
	if (BV (clib_bihash_bucket_is_empty) (b))
	continue;

	v = BV (clib_bihash_get_value) (h, b->offset);
	for (j = 0; j < (1 << b->log2_pages); j++)
	{
	for (k = 0; k < BIHASH_KVP_PER_PAGE; k++)
	{
	if (BV (clib_bihash_is_free) (&v->kvp[k]))
	continue;

	(*fp) (&v->kvp[k], arg);
	/*
	* In case the callback deletes the last entry in the bucket...
	*/
	if (BV (clib_bihash_bucket_is_empty) (b))
	goto doublebreak;
	}
	v++;
	}
	doublebreak:
	;
	}
	}

	/** @endcond */

	/*
	* fd.io coding-style-patch-verification: ON
	*
	* Local Variables:
	* eval: (c-set-style "gnu")
	* End:
	*/