Many files:

  Improved concurrency for key cache reassignment


include/my_sys.h:
  Improved concurrency for key cache reassignment
include/myisam.h:
  Improved concurrency for key cache reassignment
myisam/mi_keycache.c:
  Improved concurrency for key cache reassignment
myisam/mi_locking.c:
  Improved concurrency for key cache reassignment
mysys/mf_keycache.c:
  Improved concurrency for key cache reassignment
sql/ha_myisam.cc:
  Improved concurrency for key cache reassignment
sql/sql_table.cc:
  Improved concurrency for key cache reassignment

2 files changed, 49 insertions, 10 deletions

diff --git a/myisam/mi_keycache.c b/myisam/mi_keycache.c
index 1010aef9e1d..4b7d7d6b23f 100644
--- a/myisam/mi_keycache.c
+++ b/myisam/mi_keycache.c
@@ -39,24 +39,68 @@
     of the table will be assigned to the specified key cache.
 */
 
+typedef struct st_assign_extra_info
+{
+  pthread_mutex_t *lock; 
+  struct st_my_thread_var *waiting_thread;
+} ASSIGN_EXTRA_INFO;
+
+static void remove_key_cache_assign(void *arg)
+{
+  KEY_CACHE_VAR *key_cache= (KEY_CACHE_VAR *) arg;
+  ASSIGN_EXTRA_INFO *extra_info= (ASSIGN_EXTRA_INFO *) key_cache->extra_info;
+  struct st_my_thread_var *waiting_thread;
+  pthread_mutex_t *lock= extra_info->lock;
+  pthread_mutex_lock(lock);
+  if (!(--key_cache->assignments) && 
+      (waiting_thread = extra_info->waiting_thread))
+  {
+    my_free(extra_info, MYF(0));
+    key_cache->extra_info= 0;
+    if (waiting_thread != my_thread_var)
+      pthread_cond_signal(&waiting_thread->suspend);
+  }
+  pthread_mutex_unlock(lock);
+}
+
 int mi_assign_to_keycache(MI_INFO *info, ulonglong key_map, 
-                          KEY_CACHE_HANDLE *reg_keycache)
+                          KEY_CACHE_VAR *key_cache, 
+                          pthread_mutex_t *assign_lock)
 {
+  ASSIGN_EXTRA_INFO *extra_info;
   int error= 0;
   MYISAM_SHARE* share= info->s;
 
   DBUG_ENTER("mi_assign_to_keycache");
 
-  share->reg_keycache= reg_keycache;
+  share->reg_keycache= &key_cache->cache;
+  pthread_mutex_lock(assign_lock);
+  if (!(extra_info= (ASSIGN_EXTRA_INFO *) key_cache->extra_info))
+  {
+    if (!(extra_info= (ASSIGN_EXTRA_INFO*) my_malloc(sizeof(ASSIGN_EXTRA_INFO),
+					           MYF(MY_WME | MY_ZEROFILL))))
+      DBUG_RETURN(HA_ERR_OUT_OF_MEM);
+    key_cache->extra_info= extra_info;
+    key_cache->action= remove_key_cache_assign;
+    extra_info->lock= assign_lock;
+  }
+  key_cache->assignments++;
+  pthread_mutex_unlock(assign_lock);
+  
   if (!(info->lock_type == F_WRLCK && share->w_locks))
   {
-    if (flush_key_blocks(*share->keycache, share->kfile, FLUSH_RELEASE))
+    if (flush_key_blocks(*share->keycache, share->kfile, FLUSH_REMOVE))
     {
       error=my_errno;
       mi_mark_crashed(info);		/* Mark that table must be checked */
     }
-    share->keycache= reg_keycache;
+    share->keycache= &key_cache->cache;
   }
+  else
+  {
+    extra_info->waiting_thread= my_thread_var;
+  }
+
     
   DBUG_RETURN(error);
 }
diff --git a/myisam/mi_locking.c b/myisam/mi_locking.c
index 14d0b60741f..af0c760b706 100644
--- a/myisam/mi_locking.c
+++ b/myisam/mi_locking.c
@@ -62,17 +62,12 @@ int mi_lock_database(MI_INFO *info, int lock_type)
       /*
          During a key cache reassignment the current and registered
          key caches for the table are different.
-         Although at present key cache ressignment is always
-         performed with a shared cache for the table acquired,
-         for future possible optimizations we still
-         handle this situation as if we could come to this point 
-         during the ressignment (in non-reassignment thread).
       */ 
       if (info->lock_type == F_WRLCK && !share->w_locks &&
 	  ((switch_fl= share->keycache != share->reg_keycache) ||
            !share->delay_key_write) && 
            flush_key_blocks(*share->keycache, share->kfile,
-                            switch_fl ? FLUSH_RELEASE : FLUSH_KEEP))
+                            switch_fl ? FLUSH_REMOVE : FLUSH_KEEP))
       {
 	error=my_errno;
 	mi_mark_crashed(info);		/* Mark that table must be checked */