MDEV-5675 - Performance: my_hash_sort_bin is called too often

Reduced number of my_hash_sort_bin() calls from 4 to 1 per query.
Reduced number of memory accesses done by my_hash_sort_bin().

Details:
- let MDL subsystem use pre-calculated hash value for hash
  inserts and deletes
- let table cache use pre-calculated MDL hash value
- MDL namespace is excluded from hash value calculation, so that
  hash value can be used by table cache as is
- hash value for MDL is calculated as resulting hash value + MDL
  namespace
- extended hash implementation to accept user defined hash function

1 files changed, 20 insertions, 22 deletions

diff --git a/sql/mdl.cc b/sql/mdl.cc
index d8aa6e1d1b4..ce2483a8d8c 100644
--- a/sql/mdl.cc
+++ b/sql/mdl.cc
@@ -124,15 +124,9 @@ class MDL_map_partition
 public:
   MDL_map_partition();
   ~MDL_map_partition();
-  inline MDL_lock *find_or_insert(const MDL_key *mdl_key,
-                                  my_hash_value_type hash_value);
-  unsigned long get_lock_owner(const MDL_key *key,
-                               my_hash_value_type hash_value);
+  inline MDL_lock *find_or_insert(const MDL_key *mdl_key);
+  unsigned long get_lock_owner(const MDL_key *key);
   inline void remove(MDL_lock *lock);
-  my_hash_value_type get_key_hash(const MDL_key *mdl_key) const
-  {
-    return my_calc_hash(&m_locks, mdl_key->ptr(), mdl_key->length());
-  }
 private:
   bool move_from_hash_to_lock_mutex(MDL_lock *lock);
   /** A partition of all acquired locks in the server. */
@@ -766,13 +760,21 @@ void MDL_map::init()
 }
 
 
+my_hash_value_type mdl_hash_function(const CHARSET_INFO *cs,
+                                     const uchar *key, size_t length)
+{
+  MDL_key *mdl_key= (MDL_key*) (key - offsetof(MDL_key, m_ptr));
+  return mdl_key->hash_value();
+}
+
+
 /** Initialize the partition in the container with all MDL locks. */
 
 MDL_map_partition::MDL_map_partition()
 {
   mysql_mutex_init(key_MDL_map_mutex, &m_mutex, NULL);
-  my_hash_init(&m_locks, &my_charset_bin, 16 /* FIXME */, 0, 0,
-               mdl_locks_key, 0, 0);
+  my_hash_init2(&m_locks, 0, &my_charset_bin, 16 /* FIXME */, 0, 0,
+                mdl_locks_key, mdl_hash_function, 0, 0);
 };
 
 
@@ -846,11 +848,10 @@ MDL_lock* MDL_map::find_or_insert(const MDL_key *mdl_key)
     return lock;
   }
 
-  my_hash_value_type hash_value= m_partitions.at(0)->get_key_hash(mdl_key);
-  uint part_id= hash_value % mdl_locks_hash_partitions;
+  uint part_id= mdl_key->hash_value() % mdl_locks_hash_partitions;
   MDL_map_partition *part= m_partitions.at(part_id);
 
-  return part->find_or_insert(mdl_key, hash_value);
+  return part->find_or_insert(mdl_key);
 }
 
 
@@ -863,15 +864,14 @@ MDL_lock* MDL_map::find_or_insert(const MDL_key *mdl_key)
   @retval NULL     - Failure (OOM).
 */
 
-MDL_lock* MDL_map_partition::find_or_insert(const MDL_key *mdl_key,
-                                            my_hash_value_type hash_value)
+MDL_lock* MDL_map_partition::find_or_insert(const MDL_key *mdl_key)
 {
   MDL_lock *lock;
 
 retry:
   mysql_mutex_lock(&m_mutex);
   if (!(lock= (MDL_lock*) my_hash_search_using_hash_value(&m_locks,
-                                                          hash_value,
+                                                          mdl_key->hash_value(),
                                                           mdl_key->ptr(),
                                                           mdl_key->length())))
   {
@@ -1023,10 +1023,9 @@ MDL_map::get_lock_owner(const MDL_key *mdl_key)
   }
   else
   {
-    my_hash_value_type hash_value= m_partitions.at(0)->get_key_hash(mdl_key);
-    uint part_id= hash_value % mdl_locks_hash_partitions;
+    uint part_id= mdl_key->hash_value() % mdl_locks_hash_partitions;
     MDL_map_partition *part= m_partitions.at(part_id);
-    res= part->get_lock_owner(mdl_key, hash_value);
+    res= part->get_lock_owner(mdl_key);
   }
   return res;
 }
@@ -1034,15 +1033,14 @@ MDL_map::get_lock_owner(const MDL_key *mdl_key)
 
 
 unsigned long
-MDL_map_partition::get_lock_owner(const MDL_key *mdl_key,
-                                  my_hash_value_type hash_value)
+MDL_map_partition::get_lock_owner(const MDL_key *mdl_key)
 {
   MDL_lock *lock;
   unsigned long res= 0;
 
   mysql_mutex_lock(&m_mutex);
   lock= (MDL_lock*) my_hash_search_using_hash_value(&m_locks,
-                                                  hash_value,
+                                                  mdl_key->hash_value(),
                                                   mdl_key->ptr(),
                                                   mdl_key->length());
   if (lock)