From: Robert Haas <rhaas@postgresql.org>
Date: Tue, 29 Apr 2014 16:58:18 +0000 (-0400)
Subject: Teach sb_free to unlink spans and return their storage to fpm.
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=21cc3d7b3cfb07c3762baf7bfd1ef04b6d3e4109;p=users%2Frhaas%2Fpostgres.git

Teach sb_free to unlink spans and return their storage to fpm.

The spans themselves don't get reclaimed yet.
---

diff --git a/src/backend/utils/mmgr/sb_alloc.c b/src/backend/utils/mmgr/sb_alloc.c
index d8923fdca8..70eb9c75a0 100644
--- a/src/backend/utils/mmgr/sb_alloc.c
+++ b/src/backend/utils/mmgr/sb_alloc.c
@@ -43,7 +43,7 @@ struct sb_span
 	relptr(sb_heap) parent;		/* Containing heap. */
 	relptr(sb_span) prevspan;	/* Previous span. */
 	relptr(sb_span) nextspan;	/* Next span. */
-	relptr(char)	start;		/* Starting page number. */
+	relptr(char)	start;		/* Starting address. */
 	Size		npages;			/* Length of span in pages. */
 	uint16		size_class;		/* Size class. */
 	uint16		ninitialized;	/* Maximum number of objects ever allocated. */
@@ -125,6 +125,7 @@ static void sb_init_span(char *base, sb_span *span, sb_heap *heap,
 static void sb_out_of_memory_error(sb_allocator *a);
 static bool sb_transfer_first_span(char *base, sb_heap *heap,
 					   int fromclass, int toclass);
+static void sb_unlink_span(char *base, sb_heap *heap, sb_span *span);
 
 /*
  * Create a backend-private allocator.
@@ -322,20 +323,10 @@ sb_free(void *ptr)
 	if (span->nallocatable == 1 && span->fclass == SB_FULLNESS_CLASSES - 1)
 	{
 		sb_heap *heap = relptr_access(base, span->parent);
-		sb_span *nextspan = relptr_access(base, span->nextspan);
-		sb_span *prevspan = relptr_access(base, span->prevspan);
 		sb_span *new_nextspan;
 
-		/* Remove from current list. */
-		relptr_store(base, span->prevspan, (sb_span *) NULL);
-		if (nextspan != NULL)
-			relptr_copy(nextspan->prevspan, span->prevspan);
-		if (prevspan != NULL)
-			relptr_copy(prevspan->nextspan, span->nextspan);
-		else
-			relptr_copy(heap->spans[span->fclass], span->nextspan);
-
-		/* Add to correct list. */
+		/* Move to next lower-numbered list. */
+		sb_unlink_span(base, heap, span);
 		span->fclass = SB_FULLNESS_CLASSES - 2;
 		relptr_copy(span->nextspan, heap->spans[SB_FULLNESS_CLASSES - 2]);
 		relptr_store(base, span->prevspan, (sb_span *) NULL);
@@ -347,9 +338,17 @@ sb_free(void *ptr)
 	}
 	else if (span->nallocatable == span->nmax)
 	{
+		sb_heap *heap = relptr_access(base, span->parent);
+		Size	first_page;
+
+		sb_unlink_span(base, heap, span);
+		first_page = fpm_pointer_to_page(fpm_base,
+										 relptr_access(base, span->start));
+		FreePageManagerPut(region->fpm, first_page, span->npages);
+
 		/*
-		 * XXX. Deallocate the span; and if that causes the span of spans
-		 * to need deallocation, do that, too.
+		 * XXX. Free the span, and possibly the span-of-spans which contains
+		 * it.
 		 */
 	}
 
@@ -721,3 +720,21 @@ sb_transfer_first_span(char *base, sb_heap *heap, int fromclass, int toclass)
 
 	return true;
 }
+
+/*
+ * Remove span from current list.
+ */
+static void
+sb_unlink_span(char *base, sb_heap *heap, sb_span *span)
+{
+	sb_span *nextspan = relptr_access(base, span->nextspan);
+	sb_span *prevspan = relptr_access(base, span->prevspan);
+
+	relptr_store(base, span->prevspan, (sb_span *) NULL);
+	if (nextspan != NULL)
+		relptr_copy(nextspan->prevspan, span->prevspan);
+	if (prevspan != NULL)
+		relptr_copy(prevspan->nextspan, span->nextspan);
+	else
+		relptr_copy(heap->spans[span->fclass], span->nextspan);
+}