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postgres/src/backend/storage/buffer/xlog_bufmgr.c
Vadim B. Mikheev 5b0740d3fc WAL
2000-10-28 16:21:00 +00:00

2206 lines
53 KiB
C
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/*-------------------------------------------------------------------------
*
* bufmgr.c
* buffer manager interface routines
*
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/buffer/Attic/xlog_bufmgr.c,v 1.1 2000/10/28 16:20:56 vadim Exp $
*
*-------------------------------------------------------------------------
*/
/*
*
* BufferAlloc() -- lookup a buffer in the buffer table. If
* it isn't there add it, but do not read data into memory.
* This is used when we are about to reinitialize the
* buffer so don't care what the current disk contents are.
* BufferAlloc() also pins the new buffer in memory.
*
* ReadBuffer() -- like BufferAlloc() but reads the data
* on a buffer cache miss.
*
* ReleaseBuffer() -- unpin the buffer
*
* WriteNoReleaseBuffer() -- mark the buffer contents as "dirty"
* but don't unpin. The disk IO is delayed until buffer
* replacement.
*
* WriteBuffer() -- WriteNoReleaseBuffer() + ReleaseBuffer()
*
* BufferSync() -- flush all dirty buffers in the buffer pool.
*
* InitBufferPool() -- Init the buffer module.
*
* See other files:
* freelist.c -- chooses victim for buffer replacement
* buf_table.c -- manages the buffer lookup table
*/
#include <sys/types.h>
#include <sys/file.h>
#include <math.h>
#include <signal.h>
#include "postgres.h"
#include "executor/execdebug.h"
#include "miscadmin.h"
#include "storage/s_lock.h"
#include "storage/smgr.h"
#include "utils/relcache.h"
#ifdef XLOG
#include "catalog/pg_database.h"
#endif
#define BufferGetLSN(bufHdr) \
(*((XLogRecPtr*)MAKE_PTR((bufHdr)->data)))
extern SPINLOCK BufMgrLock;
extern long int ReadBufferCount;
extern long int ReadLocalBufferCount;
extern long int BufferHitCount;
extern long int LocalBufferHitCount;
extern long int BufferFlushCount;
extern long int LocalBufferFlushCount;
/*
* It's used to avoid disk writes for read-only transactions
* (i.e. when no one shared buffer was changed by transaction).
* We set it to true in WriteBuffer/WriteNoReleaseBuffer when
* marking shared buffer as dirty. We set it to false in xact.c
* after transaction is committed/aborted.
*/
bool SharedBufferChanged = false;
static void WaitIO(BufferDesc *buf, SPINLOCK spinlock);
static void StartBufferIO(BufferDesc *buf, bool forInput);
static void TerminateBufferIO(BufferDesc *buf);
static void ContinueBufferIO(BufferDesc *buf, bool forInput);
extern void AbortBufferIO(void);
/*
* Macro : BUFFER_IS_BROKEN
* Note that write error doesn't mean the buffer broken
*/
#define BUFFER_IS_BROKEN(buf) ((buf->flags & BM_IO_ERROR) && !(buf->flags & BM_DIRTY))
#ifndef HAS_TEST_AND_SET
static void SignalIO(BufferDesc *buf);
extern long *NWaitIOBackendP; /* defined in buf_init.c */
#endif /* HAS_TEST_AND_SET */
static Buffer ReadBufferWithBufferLock(Relation relation, BlockNumber blockNum,
bool bufferLockHeld);
static BufferDesc *BufferAlloc(Relation reln, BlockNumber blockNum,
bool *foundPtr, bool bufferLockHeld);
static int BufferReplace(BufferDesc *bufHdr);
void PrintBufferDescs(void);
/* ---------------------------------------------------
* RelationGetBufferWithBuffer
* see if the given buffer is what we want
* if yes, we don't need to bother the buffer manager
* ---------------------------------------------------
*/
Buffer
RelationGetBufferWithBuffer(Relation relation,
BlockNumber blockNumber,
Buffer buffer)
{
BufferDesc *bufHdr;
if (BufferIsValid(buffer))
{
if (!BufferIsLocal(buffer))
{
bufHdr = &BufferDescriptors[buffer - 1];
SpinAcquire(BufMgrLock);
if (bufHdr->tag.blockNum == blockNumber &&
RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node))
{
SpinRelease(BufMgrLock);
return buffer;
}
return ReadBufferWithBufferLock(relation, blockNumber, true);
}
else
{
bufHdr = &LocalBufferDescriptors[-buffer - 1];
if (bufHdr->tag.blockNum == blockNumber &&
RelFileNodeEquals(bufHdr->tag.rnode, relation->rd_node))
return buffer;
}
}
return ReadBuffer(relation, blockNumber);
}
/*
* ReadBuffer -- returns a buffer containing the requested
* block of the requested relation. If the blknum
* requested is P_NEW, extend the relation file and
* allocate a new block.
*
* Returns: the buffer number for the buffer containing
* the block read or NULL on an error.
*
* Assume when this function is called, that reln has been
* opened already.
*/
#undef ReadBuffer /* conflicts with macro when BUFMGR_DEBUG
* defined */
/*
* ReadBuffer
*
*/
Buffer
ReadBuffer(Relation reln, BlockNumber blockNum)
{
return ReadBufferWithBufferLock(reln, blockNum, false);
}
/*
* ReadBufferWithBufferLock -- does the work of
* ReadBuffer() but with the possibility that
* the buffer lock has already been held. this
* is yet another effort to reduce the number of
* semops in the system.
*/
static Buffer
ReadBufferWithBufferLock(Relation reln,
BlockNumber blockNum,
bool bufferLockHeld)
{
BufferDesc *bufHdr;
int extend; /* extending the file by one block */
int status;
bool found;
bool isLocalBuf;
extend = (blockNum == P_NEW);
isLocalBuf = reln->rd_myxactonly;
if (isLocalBuf)
{
ReadLocalBufferCount++;
bufHdr = LocalBufferAlloc(reln, blockNum, &found);
if (found)
LocalBufferHitCount++;
}
else
{
ReadBufferCount++;
/*
* lookup the buffer. IO_IN_PROGRESS is set if the requested
* block is not currently in memory.
*/
bufHdr = BufferAlloc(reln, blockNum, &found, bufferLockHeld);
if (found)
BufferHitCount++;
}
if (!bufHdr)
return InvalidBuffer;
/* if it's already in the buffer pool, we're done */
if (found)
{
/*
* This happens when a bogus buffer was returned previously and is
* floating around in the buffer pool. A routine calling this
* would want this extended.
*/
if (extend)
{
/* new buffers are zero-filled */
MemSet((char *) MAKE_PTR(bufHdr->data), 0, BLCKSZ);
smgrextend(DEFAULT_SMGR, reln,
(char *) MAKE_PTR(bufHdr->data));
}
return BufferDescriptorGetBuffer(bufHdr);
}
/*
* if we have gotten to this point, the reln pointer must be ok and
* the relation file must be open.
*/
if (extend)
{
/* new buffers are zero-filled */
MemSet((char *) MAKE_PTR(bufHdr->data), 0, BLCKSZ);
status = smgrextend(DEFAULT_SMGR, reln,
(char *) MAKE_PTR(bufHdr->data));
}
else
{
status = smgrread(DEFAULT_SMGR, reln, blockNum,
(char *) MAKE_PTR(bufHdr->data));
}
if (isLocalBuf)
return BufferDescriptorGetBuffer(bufHdr);
/* lock buffer manager again to update IO IN PROGRESS */
SpinAcquire(BufMgrLock);
if (status == SM_FAIL)
{
/* IO Failed. cleanup the data structures and go home */
if (!BufTableDelete(bufHdr))
{
SpinRelease(BufMgrLock);
elog(FATAL, "BufRead: buffer table broken after IO error\n");
}
/* remember that BufferAlloc() pinned the buffer */
UnpinBuffer(bufHdr);
/*
* Have to reset the flag so that anyone waiting for the buffer
* can tell that the contents are invalid.
*/
bufHdr->flags |= BM_IO_ERROR;
bufHdr->flags &= ~BM_IO_IN_PROGRESS;
}
else
{
/* IO Succeeded. clear the flags, finish buffer update */
bufHdr->flags &= ~(BM_IO_ERROR | BM_IO_IN_PROGRESS);
}
/* If anyone was waiting for IO to complete, wake them up now */
TerminateBufferIO(bufHdr);
SpinRelease(BufMgrLock);
if (status == SM_FAIL)
return InvalidBuffer;
return BufferDescriptorGetBuffer(bufHdr);
}
/*
* BufferAlloc -- Get a buffer from the buffer pool but dont
* read it.
*
* Returns: descriptor for buffer
*
* When this routine returns, the BufMgrLock is guaranteed NOT be held.
*/
static BufferDesc *
BufferAlloc(Relation reln,
BlockNumber blockNum,
bool *foundPtr,
bool bufferLockHeld)
{
BufferDesc *buf,
*buf2;
BufferTag newTag; /* identity of requested block */
bool inProgress; /* buffer undergoing IO */
bool newblock = FALSE;
/* create a new tag so we can lookup the buffer */
/* assume that the relation is already open */
if (blockNum == P_NEW)
{
newblock = TRUE;
blockNum = smgrnblocks(DEFAULT_SMGR, reln);
}
INIT_BUFFERTAG(&newTag, reln, blockNum);
if (!bufferLockHeld)
SpinAcquire(BufMgrLock);
/* see if the block is in the buffer pool already */
buf = BufTableLookup(&newTag);
if (buf != NULL)
{
/*
* Found it. Now, (a) pin the buffer so no one steals it from the
* buffer pool, (b) check IO_IN_PROGRESS, someone may be faulting
* the buffer into the buffer pool.
*/
PinBuffer(buf);
inProgress = (buf->flags & BM_IO_IN_PROGRESS);
*foundPtr = TRUE;
if (inProgress) /* confirm end of IO */
{
WaitIO(buf, BufMgrLock);
inProgress = (buf->flags & BM_IO_IN_PROGRESS);
}
if (BUFFER_IS_BROKEN(buf))
{
/*
* I couldn't understand the following old comment. If there's
* no IO for the buffer and the buffer is BROKEN,it should be
* read again. So start a new buffer IO here.
*
* wierd race condition:
*
* We were waiting for someone else to read the buffer. While we
* were waiting, the reader boof'd in some way, so the
* contents of the buffer are still invalid. By saying that
* we didn't find it, we can make the caller reinitialize the
* buffer. If two processes are waiting for this block, both
* will read the block. The second one to finish may
* overwrite any updates made by the first. (Assume higher
* level synchronization prevents this from happening).
*
* This is never going to happen, don't worry about it.
*/
*foundPtr = FALSE;
}
#ifdef BMTRACE
_bm_trace((reln->rd_rel->relisshared ? 0 : MyDatabaseId), RelationGetRelid(reln), blockNum, BufferDescriptorGetBuffer(buf), BMT_ALLOCFND);
#endif /* BMTRACE */
if (!(*foundPtr))
StartBufferIO(buf, true);
SpinRelease(BufMgrLock);
return buf;
}
*foundPtr = FALSE;
/*
* Didn't find it in the buffer pool. We'll have to initialize a new
* buffer. First, grab one from the free list. If it's dirty, flush
* it to disk. Remember to unlock BufMgr spinlock while doing the IOs.
*/
inProgress = FALSE;
for (buf = (BufferDesc *) NULL; buf == (BufferDesc *) NULL;)
{
buf = GetFreeBuffer();
/* GetFreeBuffer will abort if it can't find a free buffer */
Assert(buf);
/*
* There should be exactly one pin on the buffer after it is
* allocated -- ours. If it had a pin it wouldn't have been on
* the free list. No one else could have pinned it between
* GetFreeBuffer and here because we have the BufMgrLock.
*/
Assert(buf->refcount == 0);
buf->refcount = 1;
PrivateRefCount[BufferDescriptorGetBuffer(buf) - 1] = 1;
if (buf->flags & BM_DIRTY || buf->cntxDirty)
{
bool smok;
/*
* skip write error buffers
*/
if ((buf->flags & BM_IO_ERROR) != 0)
{
PrivateRefCount[BufferDescriptorGetBuffer(buf) - 1] = 0;
buf->refcount--;
buf = (BufferDesc *) NULL;
continue;
}
/*
* Set BM_IO_IN_PROGRESS to keep anyone from doing anything
* with the contents of the buffer while we write it out. We
* don't really care if they try to read it, but if they can
* complete a BufferAlloc on it they can then scribble into
* it, and we'd really like to avoid that while we are
* flushing the buffer. Setting this flag should block them
* in WaitIO until we're done.
*/
inProgress = TRUE;
/*
* All code paths that acquire this lock pin the buffer first;
* since no one had it pinned (it just came off the free
* list), no one else can have this lock.
*/
StartBufferIO(buf, false);
/*
* Write the buffer out, being careful to release BufMgrLock
* before starting the I/O.
*/
smok = BufferReplace(buf);
if (smok == FALSE)
{
elog(NOTICE, "BufferAlloc: cannot write block %u for %s/%s",
buf->tag.blockNum, buf->blind.dbname, buf->blind.relname);
inProgress = FALSE;
buf->flags |= BM_IO_ERROR;
buf->flags &= ~BM_IO_IN_PROGRESS;
TerminateBufferIO(buf);
PrivateRefCount[BufferDescriptorGetBuffer(buf) - 1] = 0;
Assert(buf->refcount > 0);
buf->refcount--;
if (buf->refcount == 0)
{
AddBufferToFreelist(buf);
buf->flags |= BM_FREE;
}
buf = (BufferDesc *) NULL;
}
else
{
/*
* BM_JUST_DIRTIED cleared by BufferReplace and shouldn't
* be setted by anyone. - vadim 01/17/97
*/
if (buf->flags & BM_JUST_DIRTIED)
{
elog(STOP, "BufferAlloc: content of block %u (%s) changed while flushing",
buf->tag.blockNum, buf->blind.relname);
}
else
buf->flags &= ~BM_DIRTY;
buf->cntxDirty = false;
}
/*
* Somebody could have pinned the buffer while we were doing
* the I/O and had given up the BufMgrLock (though they would
* be waiting for us to clear the BM_IO_IN_PROGRESS flag).
* That's why this is a loop -- if so, we need to clear the
* I/O flags, remove our pin and start all over again.
*
* People may be making buffers free at any time, so there's no
* reason to think that we have an immediate disaster on our
* hands.
*/
if (buf && buf->refcount > 1)
{
inProgress = FALSE;
buf->flags &= ~BM_IO_IN_PROGRESS;
TerminateBufferIO(buf);
PrivateRefCount[BufferDescriptorGetBuffer(buf) - 1] = 0;
buf->refcount--;
buf = (BufferDesc *) NULL;
}
/*
* Somebody could have allocated another buffer for the same
* block we are about to read in. (While we flush out the
* dirty buffer, we don't hold the lock and someone could have
* allocated another buffer for the same block. The problem is
* we haven't gotten around to insert the new tag into the
* buffer table. So we need to check here. -ay 3/95
*/
buf2 = BufTableLookup(&newTag);
if (buf2 != NULL)
{
/*
* Found it. Someone has already done what we're about to
* do. We'll just handle this as if it were found in the
* buffer pool in the first place.
*/
if (buf != NULL)
{
buf->flags &= ~BM_IO_IN_PROGRESS;
TerminateBufferIO(buf);
/* give up the buffer since we don't need it any more */
PrivateRefCount[BufferDescriptorGetBuffer(buf) - 1] = 0;
Assert(buf->refcount > 0);
buf->refcount--;
if (buf->refcount == 0)
{
AddBufferToFreelist(buf);
buf->flags |= BM_FREE;
}
}
PinBuffer(buf2);
inProgress = (buf2->flags & BM_IO_IN_PROGRESS);
*foundPtr = TRUE;
if (inProgress)
{
WaitIO(buf2, BufMgrLock);
inProgress = (buf2->flags & BM_IO_IN_PROGRESS);
}
if (BUFFER_IS_BROKEN(buf2))
*foundPtr = FALSE;
if (!(*foundPtr))
StartBufferIO(buf2, true);
SpinRelease(BufMgrLock);
return buf2;
}
}
}
/*
* At this point we should have the sole pin on a non-dirty buffer and
* we may or may not already have the BM_IO_IN_PROGRESS flag set.
*/
/*
* Change the name of the buffer in the lookup table:
*
* Need to update the lookup table before the read starts. If someone
* comes along looking for the buffer while we are reading it in, we
* don't want them to allocate a new buffer. For the same reason, we
* didn't want to erase the buf table entry for the buffer we were
* writing back until now, either.
*/
if (!BufTableDelete(buf))
{
SpinRelease(BufMgrLock);
elog(FATAL, "buffer wasn't in the buffer table\n");
}
/* record the database name and relation name for this buffer */
strcpy(buf->blind.dbname, (DatabaseName) ? DatabaseName : "Recovery");
strcpy(buf->blind.relname, RelationGetPhysicalRelationName(reln));
INIT_BUFFERTAG(&(buf->tag), reln, blockNum);
if (!BufTableInsert(buf))
{
SpinRelease(BufMgrLock);
elog(FATAL, "Buffer in lookup table twice \n");
}
/*
* Buffer contents are currently invalid. Have to mark IO IN PROGRESS
* so no one fiddles with them until the read completes. If this
* routine has been called simply to allocate a buffer, no io will be
* attempted, so the flag isnt set.
*/
if (!inProgress)
StartBufferIO(buf, true);
else
ContinueBufferIO(buf, true);
#ifdef BMTRACE
_bm_trace((reln->rd_rel->relisshared ? 0 : MyDatabaseId), RelationGetRelid(reln), blockNum, BufferDescriptorGetBuffer(buf), BMT_ALLOCNOTFND);
#endif /* BMTRACE */
SpinRelease(BufMgrLock);
return buf;
}
/*
* WriteBuffer
*
* Marks buffer contents as dirty (actual write happens later).
*
* Assume that buffer is pinned. Assume that reln is
* valid.
*
* Side Effects:
* Pin count is decremented.
*/
#undef WriteBuffer
int
WriteBuffer(Buffer buffer)
{
BufferDesc *bufHdr;
if (BufferIsLocal(buffer))
return WriteLocalBuffer(buffer, TRUE);
if (BAD_BUFFER_ID(buffer))
return FALSE;
bufHdr = &BufferDescriptors[buffer - 1];
SharedBufferChanged = true;
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
UnpinBuffer(bufHdr);
SpinRelease(BufMgrLock);
return TRUE;
}
/*
* WriteNoReleaseBuffer -- like WriteBuffer, but do not unpin the buffer
* when the operation is complete.
*/
int
WriteNoReleaseBuffer(Buffer buffer)
{
BufferDesc *bufHdr;
if (BufferIsLocal(buffer))
return WriteLocalBuffer(buffer, FALSE);
if (BAD_BUFFER_ID(buffer))
return STATUS_ERROR;
bufHdr = &BufferDescriptors[buffer - 1];
SharedBufferChanged = true;
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
SpinRelease(BufMgrLock);
return STATUS_OK;
}
#undef ReleaseAndReadBuffer
/*
* ReleaseAndReadBuffer -- combine ReleaseBuffer() and ReadBuffer()
* so that only one semop needs to be called.
*
*/
Buffer
ReleaseAndReadBuffer(Buffer buffer,
Relation relation,
BlockNumber blockNum)
{
BufferDesc *bufHdr;
Buffer retbuf;
if (BufferIsLocal(buffer))
{
Assert(LocalRefCount[-buffer - 1] > 0);
LocalRefCount[-buffer - 1]--;
}
else
{
if (BufferIsValid(buffer))
{
bufHdr = &BufferDescriptors[buffer - 1];
Assert(PrivateRefCount[buffer - 1] > 0);
PrivateRefCount[buffer - 1]--;
if (PrivateRefCount[buffer - 1] == 0)
{
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->refcount--;
if (bufHdr->refcount == 0)
{
AddBufferToFreelist(bufHdr);
bufHdr->flags |= BM_FREE;
}
retbuf = ReadBufferWithBufferLock(relation, blockNum, true);
return retbuf;
}
}
}
return ReadBuffer(relation, blockNum);
}
/*
* BufferSync -- Write all dirty buffers in the pool.
*
* This is called at checkpoint time and write out all dirty buffers.
*/
void
BufferSync()
{
int i;
BufferDesc *bufHdr;
Buffer buffer;
int status;
RelFileNode rnode;
XLogRecPtr recptr;
Relation reln = NULL;
for (i = 0, bufHdr = BufferDescriptors; i < NBuffers; i++, bufHdr++)
{
SpinAcquire(BufMgrLock);
if (!(bufHdr->flags & BM_VALID))
{
SpinRelease(BufMgrLock);
continue;
}
/*
* Pin buffer and ensure that no one reads it from disk
*/
PinBuffer(bufHdr);
/* Synchronize with BufferAlloc */
if (bufHdr->flags & BM_IO_IN_PROGRESS)
WaitIO(bufHdr, BufMgrLock);
buffer = BufferDescriptorGetBuffer(bufHdr);
rnode = bufHdr->tag.rnode;
SpinRelease(BufMgrLock);
/*
* Try to find relation for buffer
*/
reln = RelationNodeCacheGetRelation(rnode);
/*
* Protect buffer content against concurrent update
*/
LockBuffer(buffer, BUFFER_LOCK_SHARE);
/*
* Force XLOG flush for buffer' LSN
*/
recptr = BufferGetLSN(bufHdr);
XLogFlush(recptr);
/*
* Now it's safe to write buffer to disk
* (if needed at all -:))
*/
SpinAcquire(BufMgrLock);
if (bufHdr->flags & BM_IO_IN_PROGRESS)
WaitIO(bufHdr, BufMgrLock);
if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
{
bufHdr->flags &= ~BM_JUST_DIRTIED;
StartBufferIO(bufHdr, false); /* output IO start */
SpinRelease(BufMgrLock);
if (reln == (Relation) NULL)
{
status = smgrblindwrt(DEFAULT_SMGR,
bufHdr->tag.rnode,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data),
true); /* must fsync */
}
else
{
status = smgrwrite(DEFAULT_SMGR, reln,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
}
if (status == SM_FAIL) /* disk failure ?! */
elog(STOP, "BufferSync: cannot write %u for %s",
bufHdr->tag.blockNum, bufHdr->blind.relname);
/*
* Note that it's safe to change cntxDirty here because of
* we protect it from upper writers by share lock and from
* other bufmgr routines by BM_IO_IN_PROGRESS
*/
bufHdr->cntxDirty = false;
/*
* Release the per-buffer readlock, reacquire BufMgrLock.
*/
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
BufferFlushCount++;
SpinAcquire(BufMgrLock);
bufHdr->flags &= ~BM_IO_IN_PROGRESS; /* mark IO finished */
TerminateBufferIO(bufHdr); /* Sync IO finished */
/*
* If this buffer was marked by someone as DIRTY while
* we were flushing it out we must not clear DIRTY
* flag - vadim 01/17/97
*/
if (!(bufHdr->flags & BM_JUST_DIRTIED))
bufHdr->flags &= ~BM_DIRTY;
}
else
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
UnpinBuffer(bufHdr);
SpinRelease(BufMgrLock);
/* drop refcnt obtained by RelationIdCacheGetRelation */
if (reln != (Relation) NULL)
{
RelationDecrementReferenceCount(reln);
reln = NULL;
}
}
}
/*
* WaitIO -- Block until the IO_IN_PROGRESS flag on 'buf' is cleared.
*
* Should be entered with buffer manager spinlock held; releases it before
* waiting and re-acquires it afterwards.
*
* OLD NOTES:
* Because IO_IN_PROGRESS conflicts are
* expected to be rare, there is only one BufferIO
* lock in the entire system. All processes block
* on this semaphore when they try to use a buffer
* that someone else is faulting in. Whenever a
* process finishes an IO and someone is waiting for
* the buffer, BufferIO is signaled (SignalIO). All
* waiting processes then wake up and check to see
* if their buffer is now ready. This implementation
* is simple, but efficient enough if WaitIO is
* rarely called by multiple processes simultaneously.
*
* NEW NOTES:
* The above is true only on machines without test-and-set
* semaphores (which we hope are few, these days). On better
* hardware, each buffer has a spinlock that we can wait on.
*/
#ifdef HAS_TEST_AND_SET
static void
WaitIO(BufferDesc *buf, SPINLOCK spinlock)
{
/*
* Changed to wait until there's no IO - Inoue 01/13/2000
*/
while ((buf->flags & BM_IO_IN_PROGRESS) != 0)
{
SpinRelease(spinlock);
S_LOCK(&(buf->io_in_progress_lock));
S_UNLOCK(&(buf->io_in_progress_lock));
SpinAcquire(spinlock);
}
}
#else /* !HAS_TEST_AND_SET */
IpcSemaphoreId WaitIOSemId;
IpcSemaphoreId WaitCLSemId;
static void
WaitIO(BufferDesc *buf, SPINLOCK spinlock)
{
bool inProgress;
for (;;)
{
/* wait until someone releases IO lock */
(*NWaitIOBackendP)++;
SpinRelease(spinlock);
IpcSemaphoreLock(WaitIOSemId, 0, 1);
SpinAcquire(spinlock);
inProgress = (buf->flags & BM_IO_IN_PROGRESS);
if (!inProgress)
break;
}
}
/*
* SignalIO
*/
static void
SignalIO(BufferDesc *buf)
{
/* somebody better be waiting. */
Assert(buf->refcount > 1);
IpcSemaphoreUnlock(WaitIOSemId, 0, *NWaitIOBackendP);
*NWaitIOBackendP = 0;
}
#endif /* HAS_TEST_AND_SET */
long NDirectFileRead; /* some I/O's are direct file access.
* bypass bufmgr */
long NDirectFileWrite; /* e.g., I/O in psort and hashjoin. */
void
PrintBufferUsage(FILE *statfp)
{
float hitrate;
float localhitrate;
if (ReadBufferCount == 0)
hitrate = 0.0;
else
hitrate = (float) BufferHitCount *100.0 / ReadBufferCount;
if (ReadLocalBufferCount == 0)
localhitrate = 0.0;
else
localhitrate = (float) LocalBufferHitCount *100.0 / ReadLocalBufferCount;
fprintf(statfp, "!\tShared blocks: %10ld read, %10ld written, buffer hit rate = %.2f%%\n",
ReadBufferCount - BufferHitCount, BufferFlushCount, hitrate);
fprintf(statfp, "!\tLocal blocks: %10ld read, %10ld written, buffer hit rate = %.2f%%\n",
ReadLocalBufferCount - LocalBufferHitCount, LocalBufferFlushCount, localhitrate);
fprintf(statfp, "!\tDirect blocks: %10ld read, %10ld written\n",
NDirectFileRead, NDirectFileWrite);
}
void
ResetBufferUsage()
{
BufferHitCount = 0;
ReadBufferCount = 0;
BufferFlushCount = 0;
LocalBufferHitCount = 0;
ReadLocalBufferCount = 0;
LocalBufferFlushCount = 0;
NDirectFileRead = 0;
NDirectFileWrite = 0;
}
/* ----------------------------------------------
* ResetBufferPool
*
* This routine is supposed to be called when a transaction aborts.
* it will release all the buffer pins held by the transaction.
* Currently, we also call it during commit if BufferPoolCheckLeak
* detected a problem --- in that case, isCommit is TRUE, and we
* only clean up buffer pin counts.
*
* During abort, we also forget any pending fsync requests. Dirtied buffers
* will still get written, eventually, but there will be no fsync for them.
*
* ----------------------------------------------
*/
void
ResetBufferPool(bool isCommit)
{
int i;
for (i = 0; i < NBuffers; i++)
{
if (PrivateRefCount[i] != 0)
{
BufferDesc *buf = &BufferDescriptors[i];
SpinAcquire(BufMgrLock);
Assert(buf->refcount > 0);
buf->refcount--;
if (buf->refcount == 0)
{
AddBufferToFreelist(buf);
buf->flags |= BM_FREE;
}
SpinRelease(BufMgrLock);
}
PrivateRefCount[i] = 0;
}
ResetLocalBufferPool();
if (!isCommit)
smgrabort();
}
/* -----------------------------------------------
* BufferPoolCheckLeak
*
* check if there is buffer leak
*
* -----------------------------------------------
*/
int
BufferPoolCheckLeak()
{
int i;
int result = 0;
for (i = 1; i <= NBuffers; i++)
{
if (PrivateRefCount[i - 1] != 0)
{
BufferDesc *buf = &(BufferDescriptors[i - 1]);
elog(NOTICE,
"Buffer Leak: [%03d] (freeNext=%ld, freePrev=%ld, \
relname=%s, blockNum=%d, flags=0x%x, refcount=%d %ld)",
i - 1, buf->freeNext, buf->freePrev,
buf->blind.relname, buf->tag.blockNum, buf->flags,
buf->refcount, PrivateRefCount[i - 1]);
result = 1;
}
}
return result;
}
/* ------------------------------------------------
* FlushBufferPool
*
* Flush all dirty blocks in buffer pool to disk
* at the checkpoint time
* ------------------------------------------------
*/
void
FlushBufferPool(void)
{
BufferSync();
smgrsync();
}
/*
* At the commit time we have to flush local buffer pool only
*/
void
BufmgrCommit(void)
{
LocalBufferSync();
smgrcommit();
}
/*
* BufferGetBlockNumber
* Returns the block number associated with a buffer.
*
* Note:
* Assumes that the buffer is valid.
*/
BlockNumber
BufferGetBlockNumber(Buffer buffer)
{
Assert(BufferIsValid(buffer));
/* XXX should be a critical section */
if (BufferIsLocal(buffer))
return LocalBufferDescriptors[-buffer - 1].tag.blockNum;
else
return BufferDescriptors[buffer - 1].tag.blockNum;
}
/*
* BufferReplace
*
* Write out the buffer corresponding to 'bufHdr'
*
* BufMgrLock must be held at entry, and the buffer must be pinned.
*/
static int
BufferReplace(BufferDesc *bufHdr)
{
Relation reln;
XLogRecPtr recptr;
int status;
/* To check if block content changed while flushing. - vadim 01/17/97 */
bufHdr->flags &= ~BM_JUST_DIRTIED;
SpinRelease(BufMgrLock);
/*
* No need to lock buffer context - no one should be able to
* end ReadBuffer
*/
recptr = BufferGetLSN(bufHdr);
XLogFlush(recptr);
reln = RelationNodeCacheGetRelation(bufHdr->tag.rnode);
if (reln != (Relation) NULL)
{
status = smgrwrite(DEFAULT_SMGR, reln, bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
}
else
{
status = smgrblindwrt(DEFAULT_SMGR, bufHdr->tag.rnode,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data),
false); /* no fsync */
}
/* drop relcache refcnt incremented by RelationIdCacheGetRelation */
if (reln != (Relation) NULL)
RelationDecrementReferenceCount(reln);
SpinAcquire(BufMgrLock);
if (status == SM_FAIL)
return FALSE;
BufferFlushCount++;
return TRUE;
}
/*
* RelationGetNumberOfBlocks
* Returns the buffer descriptor associated with a page in a relation.
*
* Note:
* XXX may fail for huge relations.
* XXX should be elsewhere.
* XXX maybe should be hidden
*/
BlockNumber
RelationGetNumberOfBlocks(Relation relation)
{
return ((relation->rd_myxactonly) ? relation->rd_nblocks :
smgrnblocks(DEFAULT_SMGR, relation));
}
/* ---------------------------------------------------------------------
* ReleaseRelationBuffers
*
* This function removes all the buffered pages for a relation
* from the buffer pool. Dirty pages are simply dropped, without
* bothering to write them out first. This is used when the
* relation is about to be deleted. We assume that the caller
* holds an exclusive lock on the relation, which should assure
* that no new buffers will be acquired for the rel meanwhile.
*
* XXX currently it sequentially searches the buffer pool, should be
* changed to more clever ways of searching.
* --------------------------------------------------------------------
*/
void
ReleaseRelationBuffers(Relation rel)
{
int i;
BufferDesc *bufHdr;
if (rel->rd_myxactonly)
{
for (i = 0; i < NLocBuffer; i++)
{
bufHdr = &LocalBufferDescriptors[i];
if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
{
bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
bufHdr->cntxDirty = false;
LocalRefCount[i] = 0;
bufHdr->tag.rnode.relNode = InvalidOid;
}
}
return;
}
SpinAcquire(BufMgrLock);
for (i = 1; i <= NBuffers; i++)
{
bufHdr = &BufferDescriptors[i - 1];
recheck:
if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
{
/*
* If there is I/O in progress, better wait till it's done;
* don't want to delete the relation out from under someone
* who's just trying to flush the buffer!
*/
if (bufHdr->flags & BM_IO_IN_PROGRESS)
{
WaitIO(bufHdr, BufMgrLock);
/*
* By now, the buffer very possibly belongs to some other
* rel, so check again before proceeding.
*/
goto recheck;
}
/* Now we can do what we came for */
bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
bufHdr->cntxDirty = false;
/*
* Release any refcount we may have.
*
* This is very probably dead code, and if it isn't then it's
* probably wrong. I added the Assert to find out --- tgl
* 11/99.
*/
if (!(bufHdr->flags & BM_FREE))
{
/* Assert checks that buffer will actually get freed! */
Assert(PrivateRefCount[i - 1] == 1 &&
bufHdr->refcount == 1);
/* ReleaseBuffer expects we do not hold the lock at entry */
SpinRelease(BufMgrLock);
ReleaseBuffer(i);
SpinAcquire(BufMgrLock);
}
/*
* And mark the buffer as no longer occupied by this rel.
*/
BufTableDelete(bufHdr);
}
}
SpinRelease(BufMgrLock);
}
/* ---------------------------------------------------------------------
* DropBuffers
*
* This function removes all the buffers in the buffer cache for a
* particular database. Dirty pages are simply dropped, without
* bothering to write them out first. This is used when we destroy a
* database, to avoid trying to flush data to disk when the directory
* tree no longer exists. Implementation is pretty similar to
* ReleaseRelationBuffers() which is for destroying just one relation.
* --------------------------------------------------------------------
*/
void
DropBuffers(Oid dbid)
{
int i;
BufferDesc *bufHdr;
SpinAcquire(BufMgrLock);
for (i = 1; i <= NBuffers; i++)
{
bufHdr = &BufferDescriptors[i - 1];
recheck:
/*
* We know that currently database OID is tblNode but
* this probably will be changed in future and this
* func will be used to drop tablespace buffers.
*/
if (bufHdr->tag.rnode.tblNode == dbid)
{
/*
* If there is I/O in progress, better wait till it's done;
* don't want to delete the database out from under someone
* who's just trying to flush the buffer!
*/
if (bufHdr->flags & BM_IO_IN_PROGRESS)
{
WaitIO(bufHdr, BufMgrLock);
/*
* By now, the buffer very possibly belongs to some other
* DB, so check again before proceeding.
*/
goto recheck;
}
/* Now we can do what we came for */
bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
bufHdr->cntxDirty = false;
/*
* The thing should be free, if caller has checked that no
* backends are running in that database.
*/
Assert(bufHdr->flags & BM_FREE);
/*
* And mark the buffer as no longer occupied by this page.
*/
BufTableDelete(bufHdr);
}
}
SpinRelease(BufMgrLock);
}
/* -----------------------------------------------------------------
* PrintBufferDescs
*
* this function prints all the buffer descriptors, for debugging
* use only.
* -----------------------------------------------------------------
*/
void
PrintBufferDescs()
{
int i;
BufferDesc *buf = BufferDescriptors;
if (IsUnderPostmaster)
{
SpinAcquire(BufMgrLock);
for (i = 0; i < NBuffers; ++i, ++buf)
{
elog(DEBUG, "[%02d] (freeNext=%ld, freePrev=%ld, relname=%s, \
blockNum=%d, flags=0x%x, refcount=%d %ld)",
i, buf->freeNext, buf->freePrev,
buf->blind.relname, buf->tag.blockNum, buf->flags,
buf->refcount, PrivateRefCount[i]);
}
SpinRelease(BufMgrLock);
}
else
{
/* interactive backend */
for (i = 0; i < NBuffers; ++i, ++buf)
{
printf("[%-2d] (%s, %d) flags=0x%x, refcnt=%d %ld)\n",
i, buf->blind.relname, buf->tag.blockNum,
buf->flags, buf->refcount, PrivateRefCount[i]);
}
}
}
void
PrintPinnedBufs()
{
int i;
BufferDesc *buf = BufferDescriptors;
SpinAcquire(BufMgrLock);
for (i = 0; i < NBuffers; ++i, ++buf)
{
if (PrivateRefCount[i] > 0)
elog(NOTICE, "[%02d] (freeNext=%ld, freePrev=%ld, relname=%s, \
blockNum=%d, flags=0x%x, refcount=%d %ld)\n",
i, buf->freeNext, buf->freePrev, buf->blind.relname,
buf->tag.blockNum, buf->flags,
buf->refcount, PrivateRefCount[i]);
}
SpinRelease(BufMgrLock);
}
/*
* BufferPoolBlowaway
*
* this routine is solely for the purpose of experiments -- sometimes
* you may want to blowaway whatever is left from the past in buffer
* pool and start measuring some performance with a clean empty buffer
* pool.
*/
#ifdef NOT_USED
void
BufferPoolBlowaway()
{
int i;
BufferSync();
for (i = 1; i <= NBuffers; i++)
{
if (BufferIsValid(i))
{
while (BufferIsValid(i))
ReleaseBuffer(i);
}
BufTableDelete(&BufferDescriptors[i - 1]);
}
}
#endif
/* ---------------------------------------------------------------------
* FlushRelationBuffers
*
* This function flushes all dirty pages of a relation out to disk.
* Furthermore, pages that have blocknumber >= firstDelBlock are
* actually removed from the buffer pool. An error code is returned
* if we fail to dump a dirty buffer or if we find one of
* the target pages is pinned into the cache.
*
* This is used by VACUUM before truncating the relation to the given
* number of blocks. (TRUNCATE TABLE also uses it in the same way.)
* It might seem unnecessary to flush dirty pages before firstDelBlock,
* since VACUUM should already have committed its changes. However,
* it is possible for there still to be dirty pages: if some page
* had unwritten on-row tuple status updates from a prior transaction,
* and VACUUM had no additional changes to make to that page, then
* VACUUM won't have written it. This is harmless in most cases but
* will break pg_upgrade, which relies on VACUUM to ensure that *all*
* tuples have correct on-row status. So, we check and flush all
* dirty pages of the rel regardless of block number.
*
* This is also used by RENAME TABLE (with firstDelBlock = 0)
* to clear out the buffer cache before renaming the physical files of
* a relation. Without that, some other backend might try to do a
* blind write of a buffer page (relying on the BlindId of the buffer)
* and fail because it's not got the right filename anymore.
*
* In all cases, the caller should be holding AccessExclusiveLock on
* the target relation to ensure that no other backend is busy reading
* more blocks of the relation.
*
* Formerly, we considered it an error condition if we found dirty
* buffers here. However, since BufferSync no longer forces out all
* dirty buffers at every xact commit, it's possible for dirty buffers
* to still be present in the cache due to failure of an earlier
* transaction. So, must flush dirty buffers without complaint.
*
* Returns: 0 - Ok, -1 - FAILED TO WRITE DIRTY BUFFER, -2 - PINNED
*
* XXX currently it sequentially searches the buffer pool, should be
* changed to more clever ways of searching.
* --------------------------------------------------------------------
*/
int
FlushRelationBuffers(Relation rel, BlockNumber firstDelBlock)
{
int i;
BufferDesc *bufHdr;
XLogRecPtr recptr;
int status;
if (rel->rd_myxactonly)
{
for (i = 0; i < NLocBuffer; i++)
{
bufHdr = &LocalBufferDescriptors[i];
if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
{
if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
{
status = smgrwrite(DEFAULT_SMGR, rel,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
if (status == SM_FAIL)
{
elog(NOTICE, "FlushRelationBuffers(%s (local), %u): block %u is dirty, could not flush it",
RelationGetRelationName(rel), firstDelBlock,
bufHdr->tag.blockNum);
return(-1);
}
bufHdr->flags &= ~(BM_DIRTY | BM_JUST_DIRTIED);
bufHdr->cntxDirty = false;
}
if (LocalRefCount[i] > 0)
{
elog(NOTICE, "FlushRelationBuffers(%s (local), %u): block %u is referenced (%ld)",
RelationGetRelationName(rel), firstDelBlock,
bufHdr->tag.blockNum, LocalRefCount[i]);
return(-2);
}
if (bufHdr->tag.blockNum >= firstDelBlock)
{
bufHdr->tag.rnode.relNode = InvalidOid;
}
}
}
return 0;
}
SpinAcquire(BufMgrLock);
for (i = 0; i < NBuffers; i++)
{
bufHdr = &BufferDescriptors[i];
if (RelFileNodeEquals(bufHdr->tag.rnode, rel->rd_node))
{
if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
{
PinBuffer(bufHdr);
if (bufHdr->flags & BM_IO_IN_PROGRESS)
WaitIO(bufHdr, BufMgrLock);
SpinRelease(BufMgrLock);
/*
* Force XLOG flush for buffer' LSN
*/
recptr = BufferGetLSN(bufHdr);
XLogFlush(recptr);
/*
* Now it's safe to write buffer to disk
*/
SpinAcquire(BufMgrLock);
if (bufHdr->flags & BM_IO_IN_PROGRESS)
WaitIO(bufHdr, BufMgrLock);
if (bufHdr->flags & BM_DIRTY || bufHdr->cntxDirty)
{
bufHdr->flags &= ~BM_JUST_DIRTIED;
StartBufferIO(bufHdr, false); /* output IO start */
SpinRelease(BufMgrLock);
status = smgrwrite(DEFAULT_SMGR, rel,
bufHdr->tag.blockNum,
(char *) MAKE_PTR(bufHdr->data));
if (status == SM_FAIL) /* disk failure ?! */
elog(STOP, "FlushRelationBuffers: cannot write %u for %s",
bufHdr->tag.blockNum, bufHdr->blind.relname);
BufferFlushCount++;
SpinAcquire(BufMgrLock);
bufHdr->flags &= ~BM_IO_IN_PROGRESS;
TerminateBufferIO(bufHdr);
Assert(!(bufHdr->flags & BM_JUST_DIRTIED));
bufHdr->flags &= ~BM_DIRTY;
/*
* Note that it's safe to change cntxDirty here because
* of we protect it from upper writers by
* AccessExclusiveLock and from other bufmgr routines
* by BM_IO_IN_PROGRESS
*/
bufHdr->cntxDirty = false;
}
UnpinBuffer(bufHdr);
}
if (!(bufHdr->flags & BM_FREE))
{
SpinRelease(BufMgrLock);
elog(NOTICE, "FlushRelationBuffers(%s, %u): block %u is referenced (private %ld, global %d)",
RelationGetRelationName(rel), firstDelBlock,
bufHdr->tag.blockNum,
PrivateRefCount[i], bufHdr->refcount);
return -2;
}
if (bufHdr->tag.blockNum >= firstDelBlock)
{
BufTableDelete(bufHdr);
}
}
}
SpinRelease(BufMgrLock);
return 0;
}
#undef ReleaseBuffer
/*
* ReleaseBuffer -- remove the pin on a buffer without
* marking it dirty.
*
*/
int
ReleaseBuffer(Buffer buffer)
{
BufferDesc *bufHdr;
if (BufferIsLocal(buffer))
{
Assert(LocalRefCount[-buffer - 1] > 0);
LocalRefCount[-buffer - 1]--;
return STATUS_OK;
}
if (BAD_BUFFER_ID(buffer))
return STATUS_ERROR;
bufHdr = &BufferDescriptors[buffer - 1];
Assert(PrivateRefCount[buffer - 1] > 0);
PrivateRefCount[buffer - 1]--;
if (PrivateRefCount[buffer - 1] == 0)
{
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->refcount--;
if (bufHdr->refcount == 0)
{
AddBufferToFreelist(bufHdr);
bufHdr->flags |= BM_FREE;
}
SpinRelease(BufMgrLock);
}
return STATUS_OK;
}
#ifdef NOT_USED
void
IncrBufferRefCount_Debug(char *file, int line, Buffer buffer)
{
IncrBufferRefCount(buffer);
if (ShowPinTrace && !BufferIsLocal(buffer) && is_userbuffer(buffer))
{
BufferDesc *buf = &BufferDescriptors[buffer - 1];
fprintf(stderr, "PIN(Incr) %ld relname = %s, blockNum = %d, \
refcount = %ld, file: %s, line: %d\n",
buffer, buf->blind.relname, buf->tag.blockNum,
PrivateRefCount[buffer - 1], file, line);
}
}
#endif
#ifdef NOT_USED
void
ReleaseBuffer_Debug(char *file, int line, Buffer buffer)
{
ReleaseBuffer(buffer);
if (ShowPinTrace && !BufferIsLocal(buffer) && is_userbuffer(buffer))
{
BufferDesc *buf = &BufferDescriptors[buffer - 1];
fprintf(stderr, "UNPIN(Rel) %ld relname = %s, blockNum = %d, \
refcount = %ld, file: %s, line: %d\n",
buffer, buf->blind.relname, buf->tag.blockNum,
PrivateRefCount[buffer - 1], file, line);
}
}
#endif
#ifdef NOT_USED
int
ReleaseAndReadBuffer_Debug(char *file,
int line,
Buffer buffer,
Relation relation,
BlockNumber blockNum)
{
bool bufferValid;
Buffer b;
bufferValid = BufferIsValid(buffer);
b = ReleaseAndReadBuffer(buffer, relation, blockNum);
if (ShowPinTrace && bufferValid && BufferIsLocal(buffer)
&& is_userbuffer(buffer))
{
BufferDesc *buf = &BufferDescriptors[buffer - 1];
fprintf(stderr, "UNPIN(Rel&Rd) %ld relname = %s, blockNum = %d, \
refcount = %ld, file: %s, line: %d\n",
buffer, buf->blind.relname, buf->tag.blockNum,
PrivateRefCount[buffer - 1], file, line);
}
if (ShowPinTrace && BufferIsLocal(buffer) && is_userbuffer(buffer))
{
BufferDesc *buf = &BufferDescriptors[b - 1];
fprintf(stderr, "PIN(Rel&Rd) %ld relname = %s, blockNum = %d, \
refcount = %ld, file: %s, line: %d\n",
b, buf->blind.relname, buf->tag.blockNum,
PrivateRefCount[b - 1], file, line);
}
return b;
}
#endif
#ifdef BMTRACE
/*
* trace allocations and deallocations in a circular buffer in
* shared memory. check the buffer before doing the allocation,
* and die if there's anything fishy.
*/
_bm_trace(Oid dbId, Oid relId, int blkNo, int bufNo, int allocType)
{
long start,
cur;
bmtrace *tb;
start = *CurTraceBuf;
if (start > 0)
cur = start - 1;
else
cur = BMT_LIMIT - 1;
for (;;)
{
tb = &TraceBuf[cur];
if (tb->bmt_op != BMT_NOTUSED)
{
if (tb->bmt_buf == bufNo)
{
if ((tb->bmt_op == BMT_DEALLOC)
|| (tb->bmt_dbid == dbId && tb->bmt_relid == relId
&& tb->bmt_blkno == blkNo))
goto okay;
/* die holding the buffer lock */
_bm_die(dbId, relId, blkNo, bufNo, allocType, start, cur);
}
}
if (cur == start)
goto okay;
if (cur == 0)
cur = BMT_LIMIT - 1;
else
cur--;
}
okay:
tb = &TraceBuf[start];
tb->bmt_pid = MyProcPid;
tb->bmt_buf = bufNo;
tb->bmt_dbid = dbId;
tb->bmt_relid = relId;
tb->bmt_blkno = blkNo;
tb->bmt_op = allocType;
*CurTraceBuf = (start + 1) % BMT_LIMIT;
}
_bm_die(Oid dbId, Oid relId, int blkNo, int bufNo,
int allocType, long start, long cur)
{
FILE *fp;
bmtrace *tb;
int i;
tb = &TraceBuf[cur];
if ((fp = AllocateFile("/tmp/death_notice", "w")) == NULL)
elog(FATAL, "buffer alloc trace error and can't open log file");
fprintf(fp, "buffer alloc trace detected the following error:\n\n");
fprintf(fp, " buffer %d being %s inconsistently with a previous %s\n\n",
bufNo, (allocType == BMT_DEALLOC ? "deallocated" : "allocated"),
(tb->bmt_op == BMT_DEALLOC ? "deallocation" : "allocation"));
fprintf(fp, "the trace buffer contains:\n");
i = start;
for (;;)
{
tb = &TraceBuf[i];
if (tb->bmt_op != BMT_NOTUSED)
{
fprintf(fp, " [%3d]%spid %d buf %2d for <%d,%u,%d> ",
i, (i == cur ? " ---> " : "\t"),
tb->bmt_pid, tb->bmt_buf,
tb->bmt_dbid, tb->bmt_relid, tb->bmt_blkno);
switch (tb->bmt_op)
{
case BMT_ALLOCFND:
fprintf(fp, "allocate (found)\n");
break;
case BMT_ALLOCNOTFND:
fprintf(fp, "allocate (not found)\n");
break;
case BMT_DEALLOC:
fprintf(fp, "deallocate\n");
break;
default:
fprintf(fp, "unknown op type %d\n", tb->bmt_op);
break;
}
}
i = (i + 1) % BMT_LIMIT;
if (i == start)
break;
}
fprintf(fp, "\noperation causing error:\n");
fprintf(fp, "\tpid %d buf %d for <%d,%u,%d> ",
getpid(), bufNo, dbId, relId, blkNo);
switch (allocType)
{
case BMT_ALLOCFND:
fprintf(fp, "allocate (found)\n");
break;
case BMT_ALLOCNOTFND:
fprintf(fp, "allocate (not found)\n");
break;
case BMT_DEALLOC:
fprintf(fp, "deallocate\n");
break;
default:
fprintf(fp, "unknown op type %d\n", allocType);
break;
}
FreeFile(fp);
kill(getpid(), SIGILL);
}
#endif /* BMTRACE */
/*
* SetBufferCommitInfoNeedsSave
*
* Mark a buffer dirty when we have updated tuple commit-status bits in it.
*
* This is similar to WriteNoReleaseBuffer, except that we do not set
* SharedBufferChanged or BufferDirtiedByMe, because we have not made a
* critical change that has to be flushed to disk before xact commit --- the
* status-bit update could be redone by someone else just as easily. The
* buffer will be marked dirty, but it will not be written to disk until
* there is another reason to write it.
*
* This routine might get called many times on the same page, if we are making
* the first scan after commit of an xact that added/deleted many tuples.
* So, be as quick as we can if the buffer is already dirty.
*/
void
SetBufferCommitInfoNeedsSave(Buffer buffer)
{
BufferDesc *bufHdr;
if (BufferIsLocal(buffer))
return;
if (BAD_BUFFER_ID(buffer))
return;
bufHdr = &BufferDescriptors[buffer - 1];
if ((bufHdr->flags & (BM_DIRTY | BM_JUST_DIRTIED)) !=
(BM_DIRTY | BM_JUST_DIRTIED))
{
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
SpinRelease(BufMgrLock);
}
}
void
UnlockBuffers()
{
BufferDesc *buf;
int i;
for (i = 0; i < NBuffers; i++)
{
if (BufferLocks[i] == 0)
continue;
Assert(BufferIsValid(i + 1));
buf = &(BufferDescriptors[i]);
#ifdef HAS_TEST_AND_SET
S_LOCK(&(buf->cntx_lock));
#else
IpcSemaphoreLock(WaitCLSemId, 0, IpcExclusiveLock);
#endif
if (BufferLocks[i] & BL_R_LOCK)
{
Assert(buf->r_locks > 0);
(buf->r_locks)--;
}
if (BufferLocks[i] & BL_RI_LOCK)
{
/*
* Someone else could remove our RI lock when acquiring W
* lock. This is possible if we came here from elog(ERROR)
* from IpcSemaphore{Lock|Unlock}(WaitCLSemId). And so we
* don't do Assert(buf->ri_lock) here.
*/
buf->ri_lock = false;
}
if (BufferLocks[i] & BL_W_LOCK)
{
Assert(buf->w_lock);
buf->w_lock = false;
}
#ifdef HAS_TEST_AND_SET
S_UNLOCK(&(buf->cntx_lock));
#else
IpcSemaphoreUnlock(WaitCLSemId, 0, IpcExclusiveLock);
#endif
BufferLocks[i] = 0;
}
}
void
LockBuffer(Buffer buffer, int mode)
{
BufferDesc *buf;
bits8 *buflock;
Assert(BufferIsValid(buffer));
if (BufferIsLocal(buffer))
return;
buf = &(BufferDescriptors[buffer - 1]);
buflock = &(BufferLocks[buffer - 1]);
#ifdef HAS_TEST_AND_SET
S_LOCK(&(buf->cntx_lock));
#else
IpcSemaphoreLock(WaitCLSemId, 0, IpcExclusiveLock);
#endif
if (mode == BUFFER_LOCK_UNLOCK)
{
if (*buflock & BL_R_LOCK)
{
Assert(buf->r_locks > 0);
Assert(!(buf->w_lock));
Assert(!(*buflock & (BL_W_LOCK | BL_RI_LOCK)));
(buf->r_locks)--;
*buflock &= ~BL_R_LOCK;
}
else if (*buflock & BL_W_LOCK)
{
Assert(buf->w_lock);
Assert(buf->r_locks == 0);
Assert(!(*buflock & (BL_R_LOCK | BL_RI_LOCK)));
buf->w_lock = false;
*buflock &= ~BL_W_LOCK;
}
else
elog(ERROR, "UNLockBuffer: buffer %lu is not locked", buffer);
}
else if (mode == BUFFER_LOCK_SHARE)
{
unsigned i = 0;
Assert(!(*buflock & (BL_R_LOCK | BL_W_LOCK | BL_RI_LOCK)));
while (buf->ri_lock || buf->w_lock)
{
#ifdef HAS_TEST_AND_SET
S_UNLOCK(&(buf->cntx_lock));
s_lock_sleep(i++);
S_LOCK(&(buf->cntx_lock));
#else
IpcSemaphoreUnlock(WaitCLSemId, 0, IpcExclusiveLock);
s_lock_sleep(i++);
IpcSemaphoreLock(WaitCLSemId, 0, IpcExclusiveLock);
#endif
}
(buf->r_locks)++;
*buflock |= BL_R_LOCK;
}
else if (mode == BUFFER_LOCK_EXCLUSIVE)
{
unsigned i = 0;
Assert(!(*buflock & (BL_R_LOCK | BL_W_LOCK | BL_RI_LOCK)));
while (buf->r_locks > 0 || buf->w_lock)
{
if (buf->r_locks > 3 || (*buflock & BL_RI_LOCK))
{
/*
* Our RI lock might be removed by concurrent W lock
* acquiring (see what we do with RI locks below when our
* own W acquiring succeeded) and so we set RI lock again
* if we already did this.
*/
*buflock |= BL_RI_LOCK;
buf->ri_lock = true;
}
#ifdef HAS_TEST_AND_SET
S_UNLOCK(&(buf->cntx_lock));
s_lock_sleep(i++);
S_LOCK(&(buf->cntx_lock));
#else
IpcSemaphoreUnlock(WaitCLSemId, 0, IpcExclusiveLock);
s_lock_sleep(i++);
IpcSemaphoreLock(WaitCLSemId, 0, IpcExclusiveLock);
#endif
}
buf->w_lock = true;
*buflock |= BL_W_LOCK;
buf->cntxDirty = true;
if (*buflock & BL_RI_LOCK)
{
/*
* It's possible to remove RI locks acquired by another W
* lockers here, but they'll take care about it.
*/
buf->ri_lock = false;
*buflock &= ~BL_RI_LOCK;
}
}
else
elog(ERROR, "LockBuffer: unknown lock mode %d", mode);
#ifdef HAS_TEST_AND_SET
S_UNLOCK(&(buf->cntx_lock));
#else
IpcSemaphoreUnlock(WaitCLSemId, 0, IpcExclusiveLock);
#endif
}
/*
* Functions for IO error handling
*
* Note : We assume that nested buffer IO never occur.
* i.e at most one io_in_progress spinlock is held
* per proc.
*/
static BufferDesc *InProgressBuf = (BufferDesc *) NULL;
static bool IsForInput;
/*
* Function:StartBufferIO
* (Assumptions)
* My process is executing no IO
* BufMgrLock is held
* BM_IO_IN_PROGRESS mask is not set for the buffer
* The buffer is Pinned
*
*/
static void
StartBufferIO(BufferDesc *buf, bool forInput)
{
Assert(!InProgressBuf);
Assert(!(buf->flags & BM_IO_IN_PROGRESS));
buf->flags |= BM_IO_IN_PROGRESS;
#ifdef HAS_TEST_AND_SET
/*
* There used to be
*
* Assert(S_LOCK_FREE(&(buf->io_in_progress_lock)));
*
* here, but that's wrong because of the way WaitIO works: someone else
* waiting for the I/O to complete will succeed in grabbing the lock
* for a few instructions, and if we context-swap back to here the
* Assert could fail. Tiny window for failure, but I've seen it
* happen -- tgl
*/
S_LOCK(&(buf->io_in_progress_lock));
#endif /* HAS_TEST_AND_SET */
InProgressBuf = buf;
IsForInput = forInput;
}
/*
* Function:TerminateBufferIO
* (Assumptions)
* My process is executing IO for the buffer
* BufMgrLock is held
* The buffer is Pinned
*
*/
static void
TerminateBufferIO(BufferDesc *buf)
{
Assert(buf == InProgressBuf);
#ifdef HAS_TEST_AND_SET
S_UNLOCK(&(buf->io_in_progress_lock));
#else
if (buf->refcount > 1)
SignalIO(buf);
#endif /* HAS_TEST_AND_SET */
InProgressBuf = (BufferDesc *) 0;
}
/*
* Function:ContinueBufferIO
* (Assumptions)
* My process is executing IO for the buffer
* BufMgrLock is held
* The buffer is Pinned
*
*/
static void
ContinueBufferIO(BufferDesc *buf, bool forInput)
{
Assert(buf == InProgressBuf);
Assert(buf->flags & BM_IO_IN_PROGRESS);
IsForInput = forInput;
}
#ifdef NOT_USED
void
InitBufferIO(void)
{
InProgressBuf = (BufferDesc *) 0;
}
#endif
/*
* This function is called from ProcReleaseSpins().
* BufMgrLock isn't held when this function is called.
* BM_IO_ERROR is always set. If BM_IO_ERROR was already
* set in case of output,this routine would kill all
* backends and reset postmaster.
*/
void
AbortBufferIO(void)
{
BufferDesc *buf = InProgressBuf;
if (buf)
{
Assert(buf->flags & BM_IO_IN_PROGRESS);
SpinAcquire(BufMgrLock);
if (IsForInput)
Assert(!(buf->flags & BM_DIRTY) && !(buf->cntxDirty));
else
{
Assert(buf->flags & BM_DIRTY || buf->cntxDirty);
if (buf->flags & BM_IO_ERROR)
{
elog(NOTICE, "write error may be permanent: cannot write block %u for %s/%s",
buf->tag.blockNum, buf->blind.dbname, buf->blind.relname);
}
buf->flags |= BM_DIRTY;
}
buf->flags |= BM_IO_ERROR;
buf->flags &= ~BM_IO_IN_PROGRESS;
TerminateBufferIO(buf);
SpinRelease(BufMgrLock);
}
}
/*
* Cleanup buffer or mark it for cleanup. Buffer may be cleaned
* up if it's pinned only once.
*
* NOTE: buffer must be excl locked.
*/
void
MarkBufferForCleanup(Buffer buffer, void (*CleanupFunc)(Buffer))
{
BufferDesc *bufHdr = &BufferDescriptors[buffer - 1];
Assert(PrivateRefCount[buffer - 1] > 0);
if (PrivateRefCount[buffer - 1] > 1)
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
PrivateRefCount[buffer - 1]--;
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
bufHdr->CleanupFunc = CleanupFunc;
SpinRelease(BufMgrLock);
return;
}
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
if (bufHdr->refcount == 1)
{
SpinRelease(BufMgrLock);
CleanupFunc(buffer);
CleanupFunc = NULL;
}
else
SpinRelease(BufMgrLock);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
PrivateRefCount[buffer - 1]--;
SpinAcquire(BufMgrLock);
Assert(bufHdr->refcount > 0);
bufHdr->flags |= (BM_DIRTY | BM_JUST_DIRTIED);
bufHdr->CleanupFunc = CleanupFunc;
bufHdr->refcount--;
if (bufHdr->refcount == 0)
{
AddBufferToFreelist(bufHdr);
bufHdr->flags |= BM_FREE;
}
SpinRelease(BufMgrLock);
return;
}
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