From: Robert Haas <rhaas@postgresql.org>
Date: Thu, 10 Apr 2014 19:29:07 +0000 (+0000)
Subject: Remove num_size_classes.  For now, at least, it's a constant.
X-Git-Url: http://git.postgresql.org/gitweb/static/developers.postgresql.org?a=commitdiff_plain;h=7a8d51c68af74f4aacaccad742b52b2b66cd9505;p=users%2Frhaas%2Fpostgres.git

Remove num_size_classes.  For now, at least, it's a constant.
---

diff --git a/src/backend/utils/mmgr/sb_alloc.c b/src/backend/utils/mmgr/sb_alloc.c
index 5220161f01..31d4eee7c9 100644
--- a/src/backend/utils/mmgr/sb_alloc.c
+++ b/src/backend/utils/mmgr/sb_alloc.c
@@ -75,6 +75,7 @@ struct sb_span
  * the total allocations.
  */
 static const uint16 sb_size_classes[] = {
+	sizeof(sb_span), 0,				/* special size classes */
 	8, 16, 24, 32, 40, 48, 56, 64,	/* 8 classes separated by 8 bytes */
 	80, 96, 112, 128,				/* 4 classes separated by 16 bytes */
 	160, 192, 224, 256,				/* 4 classes separated by 32 bytes */
@@ -92,23 +93,21 @@ static const uint16 sb_size_classes[] = {
  * index into this array.
  */
 static char sb_size_class_map[] = {
-	0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 9, 9, 10, 10, 11, 11,
-	12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15,
-	16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17,
+	2, 3, 4, 5, 6, 7, 8, 9, 10, 10, 11, 11, 12, 12, 13, 13,
+	14, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 17, 17, 17, 17,
 	18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19,
-	20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20,
-	21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
+	20, 20, 20, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 21, 21,
 	22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
-	23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23
+	23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
+	24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
+	25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25
 };
 #define SB_SIZE_CLASS_MAP_QUANTUM	8
 
 /* Special size classes. */
 #define SB_SCLASS_SPAN_OF_SPANS			0
 #define SB_SCLASS_SPAN_LARGE			1
-#define SB_SCLASS_FIRST_REGULAR			2
-#define SB_NUM_SIZE_CLASSES \
-	(SB_SCLASS_FIRST_REGULAR + lengthof(sb_size_classes))
+#define SB_NUM_SIZE_CLASSES				lengthof(sb_size_classes)
 
 /* Helper functions. */
 static char *sb_alloc_from_heap(char *base, sb_heap *heap,
@@ -129,7 +128,6 @@ static bool sb_try_to_steal_superblock(char *base, sb_allocator *a,
 sb_allocator *
 sb_create_private_allocator(void)
 {
-	uint16	num_size_classes = lengthof(sb_size_classes);
 	Size	allocator_size;
 	int		heapno;
 	int		fclass;
@@ -137,7 +135,7 @@ sb_create_private_allocator(void)
 	char   *base = NULL;
 
 	allocator_size = offsetof(sb_allocator, heaps);
-	allocator_size += sizeof(sb_heap) * num_size_classes;
+	allocator_size += sizeof(sb_heap) * SB_NUM_SIZE_CLASSES;
 	a = malloc(allocator_size);
 	if (a == NULL)
 		ereport(ERROR,
@@ -145,8 +143,7 @@ sb_create_private_allocator(void)
 				 errmsg("out of memory")));
 
 	a->private = true;
-	a->num_size_classes = num_size_classes;
-	for (heapno = 0; heapno < num_size_classes; ++heapno)
+	for (heapno = 0; heapno < SB_NUM_SIZE_CLASSES; ++heapno)
 	{
 		sb_heap *heap = &a->heaps[heapno];
 
@@ -261,7 +258,6 @@ sb_alloc(sb_allocator *a, Size size, int flags)
 	}
 	Assert(size <= sb_size_classes[size_class]);
 	Assert(size_class == 0 || size > sb_size_classes[size_class - 1]);
-	size_class += SB_SCLASS_FIRST_REGULAR;
 
 	/* Attempt the actual allocation. */
 	result = sb_alloc_guts(base, region, a, size_class);
@@ -297,7 +293,7 @@ sb_reset_allocator(sb_allocator *a)
 	 * Iterate through heaps back to front.  We do it this way so that
 	 * spans-of-spans are freed last.
 	 */
-	for (heapno = a->num_size_classes; heapno >= 0; --heapno)
+	for (heapno = SB_NUM_SIZE_CLASSES; heapno >= 0; --heapno)
 	{
 		sb_heap *heap = &a->heaps[heapno];
 		Size	fclass;
@@ -469,18 +465,12 @@ sb_alloc_guts(char *base, sb_region *region, sb_allocator *a, int size_class)
 	Size	nmax;
 
 	/* Work out object size. */
+	Assert(size_class < SB_NUM_SIZE_CLASSES);
+	obsize = sb_size_classes[size_class];
 	if (size_class == 0)
-	{
-		obsize = sizeof(sb_span);
  		nmax = FPM_PAGE_SIZE / obsize;
-	}
 	else
-	{
-		Assert(size_class >= SB_SCLASS_FIRST_REGULAR);
-		Assert(size_class < SB_NUM_SIZE_CLASSES);
-		obsize = sb_size_classes[size_class - SB_SCLASS_FIRST_REGULAR];
  		nmax = (FPM_PAGE_SIZE * SB_PAGES_PER_SUPERBLOCK) / obsize;
-	}
 
 	/* If locking is in use, acquire the lock. */
 	if (lock != NULL)
diff --git a/src/include/utils/sb_alloc.h b/src/include/utils/sb_alloc.h
index 0ed528b6d1..cf30345136 100644
--- a/src/include/utils/sb_alloc.h
+++ b/src/include/utils/sb_alloc.h
@@ -45,15 +45,13 @@ typedef struct sb_heap
 } sb_heap;
 
 /*
- * An sb_allocator is basically just a group of heaps, N per size class, where
- * N can be chosen by the user.  If locking is required, then we've also got
- * an array of LWLocks, one per heap.
+ * An sb_allocator is basically just a group of heaps, one per size class.
+ * If locking is required, then we've also got an array of LWLocks, one per
+ * heap.
  */
 typedef struct sb_allocator
 {
 	bool	private;
-	uint16	heaps_per_size_class;
-	uint16	num_size_classes;
 	relptr(LWLock) locks;
 	sb_heap	heaps[FLEXIBLE_ARRAY_MEMBER];
 } sb_allocator;