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Implement new 'lightweight lock manager' that's intermediate between

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existing lock manager and spinlocks: it understands exclusive vs shared
lock but has few other fancy features.  Replace most uses of spinlocks
with lightweight locks.  All remaining uses of spinlocks have very short
lock hold times (a few dozen instructions), so tweak spinlock backoff
code to work efficiently given this assumption.  All per my proposal on
pghackers 26-Sep-01.
This commit is contained in:
Tom Lane
2001-09-29 04:02:27 +00:00
parent 818fb55ac4
commit 499abb0c0f
46 changed files with 1595 additions and 1355 deletions
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27
src/backend/access/transam/varsup.c
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@@ -6,7 +6,7 @@
* Copyright (c) 2000, PostgreSQL Global Development Group
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.45 2001/08/25 18:52:41 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/varsup.c,v 1.46 2001/09/29 04:02:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -15,16 +15,13 @@
#include "access/clog.h"
#include "access/transam.h"
#include "storage/ipc.h"
#include "storage/proc.h"
/* Number of OIDs to prefetch (preallocate) per XLOG write */
#define VAR_OID_PREFETCH 8192
/* Spinlocks for serializing generation of XIDs and OIDs, respectively */
SPINLOCK XidGenLockId;
SPINLOCK OidGenLockId;
/* pointer to "variable cache" in shared memory (set up by shmem.c) */
VariableCache ShmemVariableCache = NULL;
@@ -44,7 +41,7 @@ GetNewTransactionId(void)
if (AMI_OVERRIDE)
return BootstrapTransactionId;
SpinAcquire(XidGenLockId);
LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
xid = ShmemVariableCache->nextXid;
@@ -83,7 +80,7 @@ GetNewTransactionId(void)
if (MyProc != (PROC *) NULL)
MyProc->xid = xid;
SpinRelease(XidGenLockId);
LWLockRelease(XidGenLock);
return xid;
}
@@ -103,9 +100,9 @@ ReadNewTransactionId(void)
if (AMI_OVERRIDE)
return BootstrapTransactionId;
SpinAcquire(XidGenLockId);
LWLockAcquire(XidGenLock, LW_SHARED);
xid = ShmemVariableCache->nextXid;
SpinRelease(XidGenLockId);
LWLockRelease(XidGenLock);
return xid;
}
@@ -122,7 +119,7 @@ GetNewObjectId(void)
{
Oid result;
SpinAcquire(OidGenLockId);
LWLockAcquire(OidGenLock, LW_EXCLUSIVE);
/*
* Check for wraparound of the OID counter. We *must* not return 0
@@ -149,7 +146,7 @@ GetNewObjectId(void)
(ShmemVariableCache->nextOid)++;
(ShmemVariableCache->oidCount)--;
SpinRelease(OidGenLockId);
LWLockRelease(OidGenLock);
lastSeenOid = result;
@@ -162,12 +159,12 @@ CheckMaxObjectId(Oid assigned_oid)
if (lastSeenOid != InvalidOid && assigned_oid < lastSeenOid)
return;
SpinAcquire(OidGenLockId);
LWLockAcquire(OidGenLock, LW_EXCLUSIVE);
if (assigned_oid < ShmemVariableCache->nextOid)
{
lastSeenOid = ShmemVariableCache->nextOid - 1;
SpinRelease(OidGenLockId);
LWLockRelease(OidGenLock);
return;
}
@@ -178,7 +175,7 @@ CheckMaxObjectId(Oid assigned_oid)
ShmemVariableCache->oidCount -=
assigned_oid - ShmemVariableCache->nextOid + 1;
ShmemVariableCache->nextOid = assigned_oid + 1;
SpinRelease(OidGenLockId);
LWLockRelease(OidGenLock);
return;
}
@@ -192,5 +189,5 @@ CheckMaxObjectId(Oid assigned_oid)
ShmemVariableCache->nextOid = assigned_oid + 1;
ShmemVariableCache->oidCount = VAR_OID_PREFETCH - 1;
SpinRelease(OidGenLockId);
LWLockRelease(OidGenLock);
}