94 lines
2.9 KiB
C
94 lines
2.9 KiB
C
/*-------------------------------------------------------------------------
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*
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* pg_shmem.h
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* Platform-independent API for shared memory support.
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*
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* Every port is expected to support shared memory with approximately
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* SysV-ish semantics; in particular, a memory block is not anonymous
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* but has an ID, and we must be able to tell whether there are any
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* remaining processes attached to a block of a specified ID.
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*
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* To simplify life for the SysV implementation, the ID is assumed to
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* consist of two unsigned long values (these are key and ID in SysV
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* terms). Other platforms may ignore the second value if they need
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* only one ID number.
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*
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*
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* Portions Copyright (c) 1996-2023, 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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* src/include/storage/pg_shmem.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PG_SHMEM_H
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#define PG_SHMEM_H
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#include "storage/dsm_impl.h"
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typedef struct PGShmemHeader /* standard header for all Postgres shmem */
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{
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int32 magic; /* magic # to identify Postgres segments */
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#define PGShmemMagic 679834894
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pid_t creatorPID; /* PID of creating process (set but unread) */
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Size totalsize; /* total size of segment */
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Size freeoffset; /* offset to first free space */
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dsm_handle dsm_control; /* ID of dynamic shared memory control seg */
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void *index; /* pointer to ShmemIndex table */
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#ifndef WIN32 /* Windows doesn't have useful inode#s */
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dev_t device; /* device data directory is on */
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ino_t inode; /* inode number of data directory */
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#endif
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} PGShmemHeader;
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/* GUC variables */
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extern PGDLLIMPORT int shared_memory_type;
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extern PGDLLIMPORT int huge_pages;
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extern PGDLLIMPORT int huge_page_size;
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/* Possible values for huge_pages and huge_pages_status */
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typedef enum
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{
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HUGE_PAGES_OFF,
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HUGE_PAGES_ON,
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HUGE_PAGES_TRY, /* only for huge_pages */
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HUGE_PAGES_UNKNOWN, /* only for huge_pages_status */
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} HugePagesType;
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/* Possible values for shared_memory_type */
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typedef enum
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{
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SHMEM_TYPE_WINDOWS,
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SHMEM_TYPE_SYSV,
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SHMEM_TYPE_MMAP,
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} PGShmemType;
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#ifndef WIN32
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extern PGDLLIMPORT unsigned long UsedShmemSegID;
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#else
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extern PGDLLIMPORT HANDLE UsedShmemSegID;
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extern PGDLLIMPORT void *ShmemProtectiveRegion;
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#endif
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extern PGDLLIMPORT void *UsedShmemSegAddr;
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#if !defined(WIN32) && !defined(EXEC_BACKEND)
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#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_MMAP
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#elif !defined(WIN32)
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#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_SYSV
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#else
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#define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_WINDOWS
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#endif
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#ifdef EXEC_BACKEND
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extern void PGSharedMemoryReAttach(void);
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extern void PGSharedMemoryNoReAttach(void);
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#endif
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extern PGShmemHeader *PGSharedMemoryCreate(Size size,
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PGShmemHeader **shim);
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extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2);
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extern void PGSharedMemoryDetach(void);
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extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags);
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#endif /* PG_SHMEM_H */
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