From: Robert Haas <rhaas@postgresql.org>
Date: Wed, 26 Mar 2014 23:53:44 +0000 (-0700)
Subject: sb_reset_allocator
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=25a89bd4bd249d9475c042d2efb83ffdf8401893;p=users%2Frhaas%2Fpostgres.git

sb_reset_allocator
---

diff --git a/src/backend/utils/mmgr/sb_alloc.c b/src/backend/utils/mmgr/sb_alloc.c
index 30dd5c5c5c..dacb90ecae 100644
--- a/src/backend/utils/mmgr/sb_alloc.c
+++ b/src/backend/utils/mmgr/sb_alloc.c
@@ -273,6 +273,67 @@ sb_alloc(sb_allocator *a, Size size, int flags)
 	return result;		
 }
 
+/*
+ * Free all memory used by an allocator.
+ *
+ * NB: It's not safe to do this while the allocator is in use!
+ */
+void
+sb_reset_allocator(sb_allocator *a)
+{
+	char *base = NULL;
+	int	num_heaps;
+	int heapno;
+
+	/*
+	 * For shared memory allocation, pointers are relative to the start of the
+	 * region.
+	 */
+	if (!a->private)
+	{
+		sb_region *region = sb_lookup_region(a);
+		if (region == NULL)
+			elog(ERROR, "sb_region not found");
+		base = region->region_start;
+	}
+
+	/*
+	 * Iterate through heaps back to front.  We do it this way so that
+	 * spans-of-spans are freed last.
+	 */
+	num_heaps = a->heaps_per_size_class * (int) a->num_size_classes;
+	for (heapno = num_heaps; heapno >= 0; --heapno)
+	{
+		sb_heap *heap = &a->heaps[heapno];
+		Size	fclass;
+
+		for (fclass = 0; fclass < SB_FULLNESS_CLASSES; ++fclass)
+		{
+			sb_region *region;
+			char *superblock;
+			sb_span *span;
+			char *fpm_base;
+			Size first_page;
+
+			span = relptr_access(base, heap->spans[fclass]);
+			superblock = base + span->first_page * FPM_PAGE_SIZE;
+			region = sb_lookup_region(superblock);
+			Assert(region != NULL);
+			fpm_base = fpm_segment_base(region->fpm);
+			/*
+			 * XXX.  Here's where the wheels are going to come
+			 * off if it turns out that malloc returns somethign that isn't
+			 * page-aligned.... what do we do about this?  Maybe we should
+			 * rejigger things so that the fpm base is NULL for all private
+			 * stuff.
+			 */
+			first_page = (superblock - fpm_base) / FPM_PAGE_SIZE;
+			FreePageManagerPut(region->fpm, first_page, span->npages);
+
+		}
+	}
+}
+
 /*
  * Allocate an object from the provided heap.  Caller is responsible for
  * any required locking.
diff --git a/src/include/utils/sb_alloc.h b/src/include/utils/sb_alloc.h
index 5794bee4d1..0ed528b6d1 100644
--- a/src/include/utils/sb_alloc.h
+++ b/src/include/utils/sb_alloc.h
@@ -69,6 +69,7 @@ typedef struct sb_allocator
 extern sb_allocator *sb_create_private_allocator(void);
 extern void *sb_alloc(sb_allocator *, Size, int flags);
 extern void sb_free(void *ptr);
+extern void sb_reset_allocator(sb_allocator *a);
 extern void sb_destroy_private_allocator(sb_allocator *);
 
 #endif		/* SB_ALLOC_H */