Postgres95 1.01 Distribution - Virgin SourcesPG95-1_01

1 files changed, 285 insertions, 0 deletions

diff --git a/src/backend/storage/buffer/freelist.c b/src/backend/storage/buffer/freelist.c
new file mode 100644
index 00000000000..fabc3c29829
--- /dev/null
+++ b/src/backend/storage/buffer/freelist.c
@@ -0,0 +1,285 @@
+/*-------------------------------------------------------------------------
+ *
+ * freelist.c--
+ *    routines for manipulating the buffer pool's replacement strategy
+ *    freelist.
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *    $Header: /cvsroot/pgsql/src/backend/storage/buffer/freelist.c,v 1.1.1.1 1996/07/09 06:21:54 scrappy Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+/*
+ * OLD COMMENTS
+ *
+ * Data Structures:
+ *	SharedFreeList is a circular queue.  Notice that this
+ *	is a shared memory queue so the next/prev "ptrs" are
+ *	buffer ids, not addresses.
+ *
+ * Sync: all routines in this file assume that the buffer
+ * 	semaphore has been acquired by the caller.
+ */
+#include <stdio.h>
+#include "storage/bufmgr.h"
+#include "storage/buf_internals.h"	/* where declarations go */
+#include "storage/spin.h"
+#include "utils/elog.h"
+
+
+static BufferDesc 	*SharedFreeList;
+
+/* only actually used in debugging.  The lock
+ * should be acquired before calling the freelist manager.
+ */
+extern SPINLOCK BufMgrLock;
+
+#define IsInQueue(bf) \
+    Assert((bf->freeNext != INVALID_DESCRIPTOR));\
+    Assert((bf->freePrev != INVALID_DESCRIPTOR));\
+    Assert((bf->flags & BM_FREE))
+
+#define NotInQueue(bf) \
+    Assert((bf->freeNext == INVALID_DESCRIPTOR));\
+    Assert((bf->freePrev == INVALID_DESCRIPTOR));\
+    Assert(! (bf->flags & BM_FREE))
+
+
+/*
+ * AddBufferToFreelist --  
+ *
+ * In theory, this is the only routine that needs to be changed
+ * if the buffer replacement strategy changes.  Just change
+ * the manner in which buffers are added to the freelist queue.
+ * Currently, they are added on an LRU basis.
+ */
+void
+AddBufferToFreelist(BufferDesc *bf)
+{
+#ifdef BMTRACE
+    _bm_trace(bf->tag.relId.dbId, bf->tag.relId.relId, bf->tag.blockNum,
+	      BufferDescriptorGetBuffer(bf), BMT_DEALLOC);
+#endif /* BMTRACE */
+    NotInQueue(bf);
+    
+    /* change bf so it points to inFrontOfNew and its successor */
+    bf->freePrev = SharedFreeList->freePrev;
+    bf->freeNext = Free_List_Descriptor;
+    
+    /* insert new into chain */
+    BufferDescriptors[bf->freeNext].freePrev = bf->buf_id;
+    BufferDescriptors[bf->freePrev].freeNext = bf->buf_id;
+}
+
+#undef PinBuffer
+
+/*
+ * PinBuffer -- make buffer unavailable for replacement.
+ */
+void
+PinBuffer(BufferDesc *buf)
+{
+    long b;
+    
+    /* Assert (buf->refcount < 25); */
+    
+    if (buf->refcount == 0) {
+	IsInQueue(buf);
+	
+	/* remove from freelist queue */
+	BufferDescriptors[buf->freeNext].freePrev = buf->freePrev;
+	BufferDescriptors[buf->freePrev].freeNext = buf->freeNext;
+	buf->freeNext = buf->freePrev = INVALID_DESCRIPTOR;
+	
+	/* mark buffer as no longer free */
+	buf->flags &= ~BM_FREE;
+    } else {
+	NotInQueue(buf);
+    }
+    
+    b = BufferDescriptorGetBuffer(buf) - 1;
+    Assert(PrivateRefCount[b] >= 0);
+    if (PrivateRefCount[b] == 0 && LastRefCount[b] == 0)
+	buf->refcount++;
+    PrivateRefCount[b]++;
+}
+
+void
+PinBuffer_Debug(char *file, int line, BufferDesc *buf)
+{
+    PinBuffer(buf);
+    if (ShowPinTrace) {
+	Buffer buffer = BufferDescriptorGetBuffer(buf);
+	
+	fprintf(stderr, "PIN(Pin) %ld relname = %s, blockNum = %d, \
+refcount = %ld, file: %s, line: %d\n",
+		buffer, buf->sb_relname, buf->tag.blockNum,
+		PrivateRefCount[buffer - 1], file, line);
+    }
+}
+
+#undef UnpinBuffer
+
+/*
+ * UnpinBuffer -- make buffer available for replacement.
+ */
+void
+UnpinBuffer(BufferDesc *buf)
+{
+    long b = BufferDescriptorGetBuffer(buf) - 1;
+    
+    Assert(buf->refcount);
+    Assert(PrivateRefCount[b] > 0);
+    PrivateRefCount[b]--;
+    if (PrivateRefCount[b] == 0 && LastRefCount[b] == 0)
+	buf->refcount--;
+    NotInQueue(buf);
+    
+    if (buf->refcount == 0) {
+	AddBufferToFreelist(buf);
+	buf->flags |= BM_FREE;
+    } else {
+	/* do nothing */
+    }
+}
+
+void
+UnpinBuffer_Debug(char *file, int line, BufferDesc *buf)
+{
+    UnpinBuffer(buf);
+    if (ShowPinTrace) {
+	Buffer buffer = BufferDescriptorGetBuffer(buf);
+	
+	fprintf(stderr, "UNPIN(Unpin) %ld relname = %s, blockNum = %d, \
+refcount = %ld, file: %s, line: %d\n",
+		buffer, buf->sb_relname, buf->tag.blockNum,
+		PrivateRefCount[buffer - 1], file, line);
+    }
+}
+
+/*
+ * GetFreeBuffer() -- get the 'next' buffer from the freelist.
+ *
+ */
+BufferDesc *
+GetFreeBuffer()
+{
+    BufferDesc *buf;
+    
+    if (Free_List_Descriptor == SharedFreeList->freeNext) {
+	
+	/* queue is empty. All buffers in the buffer pool are pinned. */
+	elog(WARN,"out of free buffers: time to abort !\n");
+	return(NULL);
+    }
+    buf = &(BufferDescriptors[SharedFreeList->freeNext]);
+    
+    /* remove from freelist queue */
+    BufferDescriptors[buf->freeNext].freePrev = buf->freePrev;
+    BufferDescriptors[buf->freePrev].freeNext = buf->freeNext;
+    buf->freeNext = buf->freePrev = INVALID_DESCRIPTOR;
+    
+    buf->flags &= ~(BM_FREE);
+    
+    return(buf);
+}
+
+/*
+ * InitFreeList -- initialize the dummy buffer descriptor used
+ *   	as a freelist head.
+ *
+ * Assume: All of the buffers are already linked in a circular
+ *	queue.   Only called by postmaster and only during 
+ * 	initialization.
+ */
+void
+InitFreeList(bool init)
+{
+    SharedFreeList = &(BufferDescriptors[Free_List_Descriptor]);
+    
+    if (init) {
+	/* we only do this once, normally the postmaster */
+	SharedFreeList->data = INVALID_OFFSET;
+	SharedFreeList->flags = 0;
+	SharedFreeList->flags &= ~(BM_VALID | BM_DELETED | BM_FREE);
+	SharedFreeList->buf_id = Free_List_Descriptor;
+	
+	/* insert it into a random spot in the circular queue */
+	SharedFreeList->freeNext = BufferDescriptors[0].freeNext;
+	SharedFreeList->freePrev = 0;
+	BufferDescriptors[SharedFreeList->freeNext].freePrev = 
+	    BufferDescriptors[SharedFreeList->freePrev].freeNext = 
+		Free_List_Descriptor;
+    }
+}
+
+
+/*
+ * print out the free list and check for breaks.
+ */
+void
+DBG_FreeListCheck(int nfree)
+{
+    int i;
+    BufferDesc *buf;
+    
+    buf = &(BufferDescriptors[SharedFreeList->freeNext]);
+    for (i=0;i<nfree;i++,buf = &(BufferDescriptors[buf->freeNext])) {
+	
+	if (! (buf->flags & (BM_FREE))){
+	    if (buf != SharedFreeList) {
+		printf("\tfree list corrupted: %d flags %x\n",
+		       buf->buf_id,buf->flags);
+	    } else  {
+		printf("\tfree list corrupted: too short -- %d not %d\n",
+		       i,nfree);
+		
+	    }
+	    
+	    
+	}
+	if ((BufferDescriptors[buf->freeNext].freePrev != buf->buf_id) ||
+	    (BufferDescriptors[buf->freePrev].freeNext != buf->buf_id)) {
+	    printf("\tfree list links corrupted: %d %ld %ld\n",
+		   buf->buf_id,buf->freePrev,buf->freeNext);
+	}
+	
+    }
+    if (buf != SharedFreeList) {
+	printf("\tfree list corrupted: %d-th buffer is %d\n",
+	       nfree,buf->buf_id);
+	
+    }
+}
+
+/*
+ * PrintBufferFreeList -
+ *    prints the buffer free list, for debugging
+ */
+void
+PrintBufferFreeList()
+{
+    BufferDesc *buf;
+
+    if (SharedFreeList->freeNext == Free_List_Descriptor) {
+	printf("free list is empty.\n");
+	return;
+    }
+    
+    buf = &(BufferDescriptors[SharedFreeList->freeNext]);
+    for (;;) {
+	int i = (buf - BufferDescriptors);
+	printf("[%-2d] (%s, %d) flags=0x%x, refcnt=%d %ld, nxt=%ld prv=%ld)\n",
+	       i, buf->sb_relname, buf->tag.blockNum,
+	       buf->flags, buf->refcount, PrivateRefCount[i],
+	       buf->freeNext, buf->freePrev);
+	
+	if (buf->freeNext == Free_List_Descriptor)
+	    break;
+
+	buf = &(BufferDescriptors[buf->freeNext]);
+    }
+}