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fad153ec45
unnecessary cache resets. The major changes are: * When the queue overflows, we only issue a cache reset to the specific backend or backends that still haven't read the oldest message, rather than resetting everyone as in the original coding. * When we observe backend(s) falling well behind, we signal SIGUSR1 to only one backend, the one that is furthest behind and doesn't already have a signal outstanding for it. When it finishes catching up, it will in turn signal SIGUSR1 to the next-furthest-back guy, if there is one that is far enough behind to justify a signal. The PMSIGNAL_WAKEN_CHILDREN mechanism is removed. * We don't attempt to clean out dead messages after every message-receipt operation; rather, we do it on the insertion side, and only when the queue fullness passes certain thresholds. * Split SInvalLock into SInvalReadLock and SInvalWriteLock so that readers don't block writers nor vice versa (except during the infrequent queue cleanout operations). * Transfer multiple sinval messages for each acquisition of a read or write lock.
102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* lwlock.h
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* Lightweight lock manager
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*
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*
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/storage/lwlock.h,v 1.39 2008/06/19 21:32:56 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef LWLOCK_H
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#define LWLOCK_H
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/*
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* It's a bit odd to declare NUM_BUFFER_PARTITIONS and NUM_LOCK_PARTITIONS
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* here, but we need them to set up enum LWLockId correctly, and having
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* this file include lock.h or bufmgr.h would be backwards.
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*/
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/* Number of partitions of the shared buffer mapping hashtable */
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#define NUM_BUFFER_PARTITIONS 16
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/* Number of partitions the shared lock tables are divided into */
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#define LOG2_NUM_LOCK_PARTITIONS 4
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#define NUM_LOCK_PARTITIONS (1 << LOG2_NUM_LOCK_PARTITIONS)
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/*
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* We have a number of predefined LWLocks, plus a bunch of LWLocks that are
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* dynamically assigned (e.g., for shared buffers). The LWLock structures
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* live in shared memory (since they contain shared data) and are identified
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* by values of this enumerated type. We abuse the notion of an enum somewhat
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* by allowing values not listed in the enum declaration to be assigned.
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* The extra value MaxDynamicLWLock is there to keep the compiler from
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* deciding that the enum can be represented as char or short ...
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*/
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typedef enum LWLockId
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{
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BufFreelistLock,
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ShmemIndexLock,
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OidGenLock,
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XidGenLock,
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ProcArrayLock,
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SInvalReadLock,
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SInvalWriteLock,
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FreeSpaceLock,
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WALInsertLock,
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WALWriteLock,
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ControlFileLock,
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CheckpointLock,
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CLogControlLock,
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SubtransControlLock,
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MultiXactGenLock,
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MultiXactOffsetControlLock,
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MultiXactMemberControlLock,
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RelCacheInitLock,
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BgWriterCommLock,
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TwoPhaseStateLock,
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TablespaceCreateLock,
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BtreeVacuumLock,
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AddinShmemInitLock,
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AutovacuumLock,
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AutovacuumScheduleLock,
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SyncScanLock,
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/* Individual lock IDs end here */
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FirstBufMappingLock,
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FirstLockMgrLock = FirstBufMappingLock + NUM_BUFFER_PARTITIONS,
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/* must be last except for MaxDynamicLWLock: */
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NumFixedLWLocks = FirstLockMgrLock + NUM_LOCK_PARTITIONS,
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MaxDynamicLWLock = 1000000000
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} LWLockId;
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typedef enum LWLockMode
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{
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LW_EXCLUSIVE,
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LW_SHARED
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} LWLockMode;
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#ifdef LOCK_DEBUG
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extern bool Trace_lwlocks;
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#endif
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extern LWLockId LWLockAssign(void);
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extern void LWLockAcquire(LWLockId lockid, LWLockMode mode);
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extern bool LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode);
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extern void LWLockRelease(LWLockId lockid);
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extern void LWLockReleaseAll(void);
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extern bool LWLockHeldByMe(LWLockId lockid);
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extern int NumLWLocks(void);
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extern Size LWLockShmemSize(void);
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extern void CreateLWLocks(void);
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extern void RequestAddinLWLocks(int n);
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#endif /* LWLOCK_H */
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