MDEV-18734 malloc optimization for m_ordered_rootbb-10.2-midenok-MDEV-18734

- Does 1 malloc when allocating from m_ordered_root;

- init_prealloc_root() interface with user-friendly
block_size/prealloc_size parameters.

3 files changed, 44 insertions, 4 deletions

diff --git a/include/my_sys.h b/include/my_sys.h
index ac1730eeaff..6a4a321162f 100644
--- a/include/my_sys.h
+++ b/include/my_sys.h
@@ -900,6 +900,8 @@ extern void my_free_lock(void *ptr);
 #define clear_alloc_root(A) do { (A)->free= (A)->used= (A)->pre_alloc= 0; (A)->min_malloc=0;} while(0)
 extern void init_alloc_root(MEM_ROOT *mem_root, size_t block_size,
 			    size_t pre_alloc_size, myf my_flags);
+extern void init_prealloc_root(MEM_ROOT *mem_root, size_t block_size,
+                               size_t prealloc_size, myf my_flags);
 extern void *alloc_root(MEM_ROOT *mem_root, size_t Size);
 extern void *multi_alloc_root(MEM_ROOT *mem_root, ...);
 extern void free_root(MEM_ROOT *root, myf MyFLAGS);
diff --git a/mysys/my_alloc.c b/mysys/my_alloc.c
index d67b8be9bb8..a20f2969c46 100644
--- a/mysys/my_alloc.c
+++ b/mysys/my_alloc.c
@@ -89,6 +89,25 @@ void init_alloc_root(MEM_ROOT *mem_root, size_t block_size,
   DBUG_VOID_RETURN;
 }
 
+void init_prealloc_root(MEM_ROOT *mem_root, size_t block_size,
+                        size_t prealloc_size, myf my_flags)
+{
+  size_t pre_alloc;
+  init_alloc_root(mem_root, block_size + ALLOC_ROOT_MIN_BLOCK_SIZE, 0, my_flags);
+  if (!prealloc_size)
+    return;
+  pre_alloc= prealloc_size + (prealloc_size / block_size + 1) * ALLOC_ROOT_MIN_BLOCK_SIZE;
+  if ((mem_root->free= mem_root->pre_alloc=
+        (USED_MEM*) my_malloc(pre_alloc + ALIGN_SIZE(sizeof(USED_MEM)),
+                              MYF(my_flags))))
+  {
+    mem_root->free->size= pre_alloc + ALIGN_SIZE(sizeof(USED_MEM));
+    mem_root->free->left= pre_alloc;
+    mem_root->free->next= 0;
+    TRASH_MEM(mem_root->free);
+  }
+}
+
 /*
   SYNOPSIS
     reset_root_defaults()
diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index cdd17efaa20..fe9c0033262 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -5132,7 +5132,20 @@ bool ha_partition::init_record_priority_queue()
   /* Allocate a key for temporary use when setting up the scan. */
   alloc_len+= table_share->max_key_length;
 
-  init_alloc_root(&m_ordered_root, 512, 0, MYF(MY_WME));
+  size_t storage_size;
+  if (table->s->blob_fields)
+  {
+    size_t block_size, prealloc_size;
+    storage_size= table->s->blob_fields * sizeof(Ordered_blob_storage *);
+    block_size= storage_size < sizeof(Ordered_blob_storage) ?
+      storage_size : sizeof(Ordered_blob_storage);
+    prealloc_size= alloc_len + used_parts * (storage_size +
+      table->s->blob_fields * sizeof(Ordered_blob_storage));
+    DBUG_ASSERT(block_size > 0);
+    init_prealloc_root(&m_ordered_root, block_size, prealloc_size, MYF(MY_WME));
+  }
+  else
+    init_prealloc_root(&m_ordered_root, alloc_len, 0, MYF(MY_WME));
 
   if (!(m_ordered_rec_buffer= (uchar*) alloc_root(&m_ordered_root, alloc_len)))
     DBUG_RETURN(true);
@@ -5154,9 +5167,15 @@ bool ha_partition::init_record_priority_queue()
     if (table->s->blob_fields)
     {
       Ordered_blob_storage **blob_storage= (Ordered_blob_storage **)
-        alloc_root(&m_ordered_root, table->s->blob_fields * sizeof(Ordered_blob_storage *));
-      for (uint i= 0; i < table->s->blob_fields; ++i)
-        blob_storage[i]= new (&m_ordered_root) Ordered_blob_storage;
+        alloc_root(&m_ordered_root, storage_size);
+      if (!blob_storage)
+        DBUG_RETURN(true);
+      for (uint j= 0; j < table->s->blob_fields; ++j)
+      {
+        blob_storage[j]= new (&m_ordered_root) Ordered_blob_storage;
+        if (!blob_storage[j])
+          DBUG_RETURN(true);
+      }
       *((Ordered_blob_storage ***) ptr)= blob_storage;
     }
     int2store(ptr + sizeof(String **), i);