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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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25
src/backend/access/transam/xact.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.110 2001/09/28 08:08:57 thomas Exp $
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.111 2001/09/29 04:02:21 tgl Exp $
*
* NOTES
* Transaction aborts can now occur two ways:
@ -965,7 +965,7 @@ CommitTransaction(void)
* this must be done _before_ releasing locks we hold and _after_
* RecordTransactionCommit.
*
* SpinAcquire(SInvalLock) is required: UPDATE with xid 0 is blocked
* LWLockAcquire(SInvalLock) is required: UPDATE with xid 0 is blocked
* by xid 1' UPDATE, xid 1 is doing commit while xid 2 gets snapshot -
* if xid 2' GetSnapshotData sees xid 1 as running then it must see
* xid 0 as running as well or it will see two tuple versions - one
@ -975,10 +975,10 @@ CommitTransaction(void)
if (MyProc != (PROC *) NULL)
{
/* Lock SInvalLock because that's what GetSnapshotData uses. */
SpinAcquire(SInvalLock);
LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
SpinRelease(SInvalLock);
LWLockRelease(SInvalLock);
}
/*
@ -1030,12 +1030,15 @@ AbortTransaction(void)
HOLD_INTERRUPTS();
/*
* Release any spinlocks or buffer context locks we might be holding
* as quickly as possible. (Real locks, however, must be held till we
* finish aborting.) Releasing spinlocks is critical since we might
* try to grab them again while cleaning up!
* Release any LW locks we might be holding as quickly as possible.
* (Regular locks, however, must be held till we finish aborting.)
* Releasing LW locks is critical since we might try to grab them again
* while cleaning up!
*/
ProcReleaseSpins(NULL);
LWLockReleaseAll();
/* Clean up buffer I/O and buffer context locks, too */
AbortBufferIO();
UnlockBuffers();
/*
@ -1081,10 +1084,10 @@ AbortTransaction(void)
if (MyProc != (PROC *) NULL)
{
/* Lock SInvalLock because that's what GetSnapshotData uses. */
SpinAcquire(SInvalLock);
LWLockAcquire(SInvalLock, LW_EXCLUSIVE);
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
SpinRelease(SInvalLock);
LWLockRelease(SInvalLock);
}
RelationPurgeLocalRelation(false);