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This patch extracts page buffer pooling and the simple

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least-recently-used strategy from clog.c into slru.c.  It doesn't
change any visible behaviour and passes all regression tests plus a
TruncateCLOG test done manually.

Apart from refactoring I made a little change to SlruRecentlyUsed,
formerly ClogRecentlyUsed:  It now skips incrementing lru_counts, if
slotno is already the LRU slot, thus saving a few CPU cycles.  To make
this work, lru_counts are initialised to 1 in SimpleLruInit.

SimpleLru will be used by pg_subtrans (part of the nested transactions
project), so the main purpose of this patch is to avoid future code
duplication.

Manfred Koizar
This commit is contained in:
Bruce Momjian
2003-06-11 22:37:46 +00:00
parent 240dc5cddc
commit 0abe7431c6
6 changed files with 990 additions and 799 deletions
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62
src/include/access/slru.h Normal file
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/*
* slru.h
*
* Simple LRU
*
* Portions Copyright (c) 2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: slru.h,v 1.1 2003/06/11 22:37:46 momjian Exp $
*/
#ifndef SLRU_H
#define SLRU_H
#include "access/xlog.h"
/* exported because lwlock.c needs it */
#define NUM_CLOG_BUFFERS 8
typedef struct SlruLockData
{
LWLockId ControlLock;
/*
* BufferLocks is set during CLOGShmemInit and does not change thereafter.
* The value is automatically inherited by backends via fork, and
* doesn't need to be in shared memory.
*/
LWLockId BufferLocks[NUM_CLOG_BUFFERS]; /* Per-buffer I/O locks */
} SlruLockData;
typedef SlruLockData *SlruLock;
typedef struct SlruCtlData
{
void *shared; /* pointer to SlruSharedData */
SlruLock locks;
/*
* Dir is set during SimpleLruShmemInit and does not change thereafter.
* The value is automatically inherited by backends via fork, and
* doesn't need to be in shared memory.
*/
char Dir[MAXPGPATH];
/*
* Decide which of two page numbers is "older" for truncation purposes.
* We need to use comparison of TransactionIds here in order to do the right
* thing with wraparound XID arithmetic.
*/
bool (*PagePrecedes)(int, int);
} SlruCtlData;
typedef SlruCtlData *SlruCtl;
extern int SimpleLruShmemSize(void);
extern void SimpleLruInit(SlruCtl ctl, const char *name, const char *subdir);
extern int SimpleLruZeroPage(SlruCtl ctl, int pageno);
extern char *SimpleLruReadPage(SlruCtl ctl, int pageno, TransactionId xid, bool forwrite);
extern void SimpleLruWritePage(SlruCtl ctl, int slotno);
extern void SimpleLruSetLatestPage(SlruCtl ctl, int pageno);
extern void SimpleLruFlush(SlruCtl ctl, bool checkpoint);
extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);
#endif /* SLRU_H */