(#538) Unit-test to exercise mini_allocator. Minor cleanup of module.

This commit does some minor cleanup of the mini-allocator module.
Some interfaces are slightly changed to streamline init / deinit
interfaces. A new unit-test is added to exercise core interfaces
of this page allocation system, and to exercise / test the print
methods for keyed and unkeyed page allocation schemes.

Extend print methods to also print page_addr and extent_addr as
page_num and extent_num, where applicable.

Makefile

@@ -462,6 +462,10 @@ $(BINDIR)/$(UNITDIR)/platform_apis_test: $(UTIL_SYS)               \
                                          $(COMMON_UNIT_TESTOBJ)    \
                                          $(PLATFORM_SYS)
 
+$(BINDIR)/$(UNITDIR)/mini_allocator_test: $(COMMON_TESTOBJ)                             \
+                                          $(OBJDIR)/$(FUNCTIONAL_TESTSDIR)/test_async.o \
+                                          $(LIBDIR)/libsplinterdb.so
+
 ########################################
 # Convenience mini unit-test targets
 unit/util_test:                    $(BINDIR)/$(UNITDIR)/util_test

src/allocator.h

@@ -253,6 +253,23 @@ allocator_print_allocated(allocator *al)
    return al->ops->print_allocated(al);
 }
 
+// Return the address of the extent holding page at address 'addr'
+static inline uint64
+allocator_extent_base_addr(allocator *al, uint64 addr)
+{
+   allocator_config *allocator_cfg = allocator_get_config(al);
+   return allocator_config_extent_base_addr(allocator_cfg, addr);
+}
+
+// Returns the address of the page next to input 'page_addr'
+static inline uint64
+allocator_next_page_addr(allocator *al, uint64 page_addr)
+{
+   allocator_config *allocator_cfg = allocator_get_config(al);
+   return (page_addr + allocator_cfg->io_cfg->page_size);
+}
+
+
 static inline bool
 allocator_page_valid(allocator *al, uint64 addr)
 {

src/btree.c

@@ -1016,8 +1016,11 @@ btree_truncate_index(const btree_config *cfg, // IN
  *-----------------------------------------------------------------------------
  * btree_alloc --
  *
- *      Allocates a node from the preallocator. Will refill it if there are no
- *      more nodes available for the given height.
+ *      Allocates a new page from the mini-allocator for a new BTree node.
+ *      from the (previously setup) mini-allocator. Will refill the mini-
+ *      allocator's cache of pre-allocated extents if there are no more nodes
+ *      (pages) available from the already-allocated extent for the given
+ *      height.
  *-----------------------------------------------------------------------------
  */
 bool