1 /*------------------------------------------------------------------------- 2 * 3 * pg_shmem.h 4 * Platform-independent API for shared memory support. 5 * 6 * Every port is expected to support shared memory with approximately 7 * SysV-ish semantics; in particular, a memory block is not anonymous 8 * but has an ID, and we must be able to tell whether there are any 9 * remaining processes attached to a block of a specified ID. 10 * 11 * To simplify life for the SysV implementation, the ID is assumed to 12 * consist of two unsigned long values (these are key and ID in SysV 13 * terms). Other platforms may ignore the second value if they need 14 * only one ID number. 15 * 16 * 17 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group 18 * Portions Copyright (c) 1994, Regents of the University of California 19 * 20 * src/include/storage/pg_shmem.h 21 * 22 *------------------------------------------------------------------------- 23 */ 24 #ifndef PG_SHMEM_H 25 #define PG_SHMEM_H 26 27 #include "storage/dsm_impl.h" 28 29 typedef struct PGShmemHeader /* standard header for all Postgres shmem */ 30 { 31 int32 magic; /* magic # to identify Postgres segments */ 32 #define PGShmemMagic 679834894 33 pid_t creatorPID; /* PID of creating process (set but unread) */ 34 Size totalsize; /* total size of segment */ 35 Size freeoffset; /* offset to first free space */ 36 dsm_handle dsm_control; /* ID of dynamic shared memory control seg */ 37 void *index; /* pointer to ShmemIndex table */ 38 #ifndef WIN32 /* Windows doesn't have useful inode#s */ 39 dev_t device; /* device data directory is on */ 40 ino_t inode; /* inode number of data directory */ 41 #endif 42 } PGShmemHeader; 43 44 /* GUC variables */ 45 extern int shared_memory_type; 46 extern int huge_pages; 47 extern int huge_page_size; 48 49 /* Possible values for huge_pages */ 50 typedef enum 51 { 52 HUGE_PAGES_OFF, 53 HUGE_PAGES_ON, 54 HUGE_PAGES_TRY 55 } HugePagesType; 56 57 /* Possible values for shared_memory_type */ 58 typedef enum 59 { 60 SHMEM_TYPE_WINDOWS, 61 SHMEM_TYPE_SYSV, 62 SHMEM_TYPE_MMAP 63 } PGShmemType; 64 65 #ifndef WIN32 66 extern unsigned long UsedShmemSegID; 67 #else 68 extern HANDLE UsedShmemSegID; 69 extern void *ShmemProtectiveRegion; 70 #endif 71 extern void *UsedShmemSegAddr; 72 73 #if !defined(WIN32) && !defined(EXEC_BACKEND) 74 #define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_MMAP 75 #elif !defined(WIN32) 76 #define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_SYSV 77 #else 78 #define DEFAULT_SHARED_MEMORY_TYPE SHMEM_TYPE_WINDOWS 79 #endif 80 81 #ifdef EXEC_BACKEND 82 extern void PGSharedMemoryReAttach(void); 83 extern void PGSharedMemoryNoReAttach(void); 84 #endif 85 86 extern PGShmemHeader *PGSharedMemoryCreate(Size size, 87 PGShmemHeader **shim); 88 extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); 89 extern void PGSharedMemoryDetach(void); 90 91 #endif /* PG_SHMEM_H */ 92