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Remove BufferLocks[] array in favor of a single pointer to the buffer

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(if any) currently waited for by LockBufferForCleanup(), which is all
that we were using it for anymore.  Saves some space and eliminates
proportional-to-NBuffers slowdown in UnlockBuffers().
This commit is contained in:
Tom Lane
2004-10-16 18:05:07 +00:00
parent 72f9013741
commit 1c2de47746
3 changed files with 35 additions and 56 deletions
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68
src/backend/storage/buffer/bufmgr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.178 2004/10/15 22:39:59 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.179 2004/10/16 18:05:06 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -66,6 +66,13 @@ long NDirectFileRead; /* some I/O's are direct file access.
long NDirectFileWrite; /* e.g., I/O in psort and hashjoin. */
/* local state for StartBufferIO and related functions */
static BufferDesc *InProgressBuf = NULL;
static bool IsForInput;
/* local state for LockBufferForCleanup */
static BufferDesc *PinCountWaitBuf = NULL;
static void PinBuffer(BufferDesc *buf, bool fixOwner);
static void UnpinBuffer(BufferDesc *buf, bool fixOwner);
static void WaitIO(BufferDesc *buf);
@ -1650,48 +1657,38 @@ SetBufferCommitInfoNeedsSave(Buffer buffer)
* Release buffer context locks for shared buffers.
*
* Used to clean up after errors.
*
* Currently, we can expect that lwlock.c's LWLockReleaseAll() took care
* of releasing buffer context locks per se; the only thing we need to deal
* with here is clearing any PIN_COUNT request that was in progress.
*/
void
UnlockBuffers(void)
{
BufferDesc *buf;
int i;
BufferDesc *buf = PinCountWaitBuf;
for (i = 0; i < NBuffers; i++)
if (buf)
{
bits8 buflocks = BufferLocks[i];
if (buflocks == 0)
continue;
buf = &(BufferDescriptors[i]);
HOLD_INTERRUPTS(); /* don't want to die() partway through... */
LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
/*
* The buffer's cntx_lock has already been released by lwlock.c.
* Don't complain if flag bit not set; it could have been
* reset but we got a cancel/die interrupt before getting the
* signal.
*/
if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
buf->wait_backend_id == MyBackendId)
buf->flags &= ~BM_PIN_COUNT_WAITER;
LWLockRelease(BufMgrLock);
if (buflocks & BL_PIN_COUNT_LOCK)
{
LWLockAcquire(BufMgrLock, LW_EXCLUSIVE);
/*
* Don't complain if flag bit not set; it could have been
* reset but we got a cancel/die interrupt before getting the
* signal.
*/
if ((buf->flags & BM_PIN_COUNT_WAITER) != 0 &&
buf->wait_backend_id == MyBackendId)
buf->flags &= ~BM_PIN_COUNT_WAITER;
LWLockRelease(BufMgrLock);
ProcCancelWaitForSignal();
}
BufferLocks[i] = 0;
ProcCancelWaitForSignal();
RESUME_INTERRUPTS();
}
PinCountWaitBuf = NULL;
}
/*
@ -1779,9 +1776,9 @@ void
LockBufferForCleanup(Buffer buffer)
{
BufferDesc *bufHdr;
bits8 *buflock;
Assert(BufferIsValid(buffer));
Assert(PinCountWaitBuf == NULL);
if (BufferIsLocal(buffer))
{
@ -1799,7 +1796,6 @@ LockBufferForCleanup(Buffer buffer)
PrivateRefCount[buffer - 1]);
bufHdr = &BufferDescriptors[buffer - 1];
buflock = &(BufferLocks[buffer - 1]);
for (;;)
{
@ -1822,12 +1818,12 @@ LockBufferForCleanup(Buffer buffer)
}
bufHdr->wait_backend_id = MyBackendId;
bufHdr->flags |= BM_PIN_COUNT_WAITER;
*buflock |= BL_PIN_COUNT_LOCK;
PinCountWaitBuf = bufHdr;
LWLockRelease(BufMgrLock);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/* Wait to be signaled by UnpinBuffer() */
ProcWaitForSignal();
*buflock &= ~BL_PIN_COUNT_LOCK;
PinCountWaitBuf = NULL;
/* Loop back and try again */
}
}
@ -1835,11 +1831,9 @@ LockBufferForCleanup(Buffer buffer)
/*
* Functions for IO error handling
*
* Note : We assume that nested buffer IO never occur.
* Note: We assume that nested buffer IO never occurs.
* i.e at most one io_in_progress lock is held per proc.
*/
static BufferDesc *InProgressBuf = NULL;
static bool IsForInput;
*/
/*
* Function:StartBufferIO