codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * slru.h4 *		Simple LRU buffering for transaction status logfiles5 *6 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group7 * Portions Copyright (c) 1994, Regents of the University of California8 *9 * src/include/access/slru.h10 *11 *-------------------------------------------------------------------------12 */13#ifndef SLRU_H14#define SLRU_H15 16#include "access/xlogdefs.h"17#include "storage/lwlock.h"18#include "storage/sync.h"19 20 21/*22 * Define SLRU segment size.  A page is the same BLCKSZ as is used everywhere23 * else in Postgres.  The segment size can be chosen somewhat arbitrarily;24 * we make it 32 pages by default, or 256Kb, i.e. 1M transactions for CLOG25 * or 64K transactions for SUBTRANS.26 *27 * Note: because TransactionIds are 32 bits and wrap around at 0xFFFFFFFF,28 * page numbering also wraps around at 0xFFFFFFFF/xxxx_XACTS_PER_PAGE (where29 * xxxx is CLOG or SUBTRANS, respectively), and segment numbering at30 * 0xFFFFFFFF/xxxx_XACTS_PER_PAGE/SLRU_PAGES_PER_SEGMENT.  We need31 * take no explicit notice of that fact in slru.c, except when comparing32 * segment and page numbers in SimpleLruTruncate (see PagePrecedes()).33 */34#define SLRU_PAGES_PER_SEGMENT	3235 36/*37 * Page status codes.  Note that these do not include the "dirty" bit.38 * page_dirty can be true only in the VALID or WRITE_IN_PROGRESS states;39 * in the latter case it implies that the page has been re-dirtied since40 * the write started.41 */42typedef enum43{44	SLRU_PAGE_EMPTY,			/* buffer is not in use */45	SLRU_PAGE_READ_IN_PROGRESS, /* page is being read in */46	SLRU_PAGE_VALID,			/* page is valid and not being written */47	SLRU_PAGE_WRITE_IN_PROGRESS /* page is being written out */48} SlruPageStatus;49 50/*51 * Shared-memory state52 */53typedef struct SlruSharedData54{55	LWLock	   *ControlLock;56 57	/* Number of buffers managed by this SLRU structure */58	int			num_slots;59 60	/*61	 * Arrays holding info for each buffer slot.  Page number is undefined62	 * when status is EMPTY, as is page_lru_count.63	 */64	char	  **page_buffer;65	SlruPageStatus *page_status;66	bool	   *page_dirty;67	int		   *page_number;68	int		   *page_lru_count;69	LWLockPadded *buffer_locks;70 71	/*72	 * Optional array of WAL flush LSNs associated with entries in the SLRU73	 * pages.  If not zero/NULL, we must flush WAL before writing pages (true74	 * for pg_xact, false for multixact, pg_subtrans, pg_notify).  group_lsn[]75	 * has lsn_groups_per_page entries per buffer slot, each containing the76	 * highest LSN known for a contiguous group of SLRU entries on that slot's77	 * page.78	 */79	XLogRecPtr *group_lsn;80	int			lsn_groups_per_page;81 82	/*----------83	 * We mark a page "most recently used" by setting84	 *		page_lru_count[slotno] = ++cur_lru_count;85	 * The oldest page is therefore the one with the highest value of86	 *		cur_lru_count - page_lru_count[slotno]87	 * The counts will eventually wrap around, but this calculation still88	 * works as long as no page's age exceeds INT_MAX counts.89	 *----------90	 */91	int			cur_lru_count;92 93	/*94	 * latest_page_number is the page number of the current end of the log;95	 * this is not critical data, since we use it only to avoid swapping out96	 * the latest page.97	 */98	int			latest_page_number;99 100	/* SLRU's index for statistics purposes (might not be unique) */101	int			slru_stats_idx;102} SlruSharedData;103 104typedef SlruSharedData *SlruShared;105 106/*107 * SlruCtlData is an unshared structure that points to the active information108 * in shared memory.109 */110typedef struct SlruCtlData111{112	SlruShared	shared;113 114	/*115	 * Which sync handler function to use when handing sync requests over to116	 * the checkpointer.  SYNC_HANDLER_NONE to disable fsync (eg pg_notify).117	 */118	SyncRequestHandler sync_handler;119 120	/*121	 * Decide whether a page is "older" for truncation and as a hint for122	 * evicting pages in LRU order.  Return true if every entry of the first123	 * argument is older than every entry of the second argument.  Note that124	 * !PagePrecedes(a,b) && !PagePrecedes(b,a) need not imply a==b; it also125	 * arises when some entries are older and some are not.  For SLRUs using126	 * SimpleLruTruncate(), this must use modular arithmetic.  (For others,127	 * the behavior of this callback has no functional implications.)  Use128	 * SlruPagePrecedesUnitTests() in SLRUs meeting its criteria.129	 */130	bool		(*PagePrecedes) (int, int);131 132	/*133	 * Dir is set during SimpleLruInit and does not change thereafter. Since134	 * it's always the same, it doesn't need to be in shared memory.135	 */136	char		Dir[64];137} SlruCtlData;138 139typedef SlruCtlData *SlruCtl;140 141 142extern Size SimpleLruShmemSize(int nslots, int nlsns);143extern void SimpleLruInit(SlruCtl ctl, const char *name, int nslots, int nlsns,144						  LWLock *ctllock, const char *subdir, int tranche_id,145						  SyncRequestHandler sync_handler);146extern int	SimpleLruZeroPage(SlruCtl ctl, int pageno);147extern int	SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,148							  TransactionId xid);149extern int	SimpleLruReadPage_ReadOnly(SlruCtl ctl, int pageno,150									   TransactionId xid);151extern void SimpleLruWritePage(SlruCtl ctl, int slotno);152extern void SimpleLruWriteAll(SlruCtl ctl, bool allow_redirtied);153#ifdef USE_ASSERT_CHECKING154extern void SlruPagePrecedesUnitTests(SlruCtl ctl, int per_page);155#else156#define SlruPagePrecedesUnitTests(ctl, per_page) do {} while (0)157#endif158extern void SimpleLruTruncate(SlruCtl ctl, int cutoffPage);159extern bool SimpleLruDoesPhysicalPageExist(SlruCtl ctl, int pageno);160 161typedef bool (*SlruScanCallback) (SlruCtl ctl, char *filename, int segpage,162								  void *data);163extern bool SlruScanDirectory(SlruCtl ctl, SlruScanCallback callback, void *data);164extern void SlruDeleteSegment(SlruCtl ctl, int segno);165 166extern int	SlruSyncFileTag(SlruCtl ctl, const FileTag *ftag, char *path);167 168/* SlruScanDirectory public callbacks */169extern bool SlruScanDirCbReportPresence(SlruCtl ctl, char *filename,170										int segpage, void *data);171extern bool SlruScanDirCbDeleteAll(SlruCtl ctl, char *filename, int segpage,172								   void *data);173 174#endif							/* SLRU_H */175