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) 1996-2016, 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 variable */ 45 extern int huge_pages; 46 47 /* Possible values for huge_pages */ 48 typedef enum 49 { 50 HUGE_PAGES_OFF, 51 HUGE_PAGES_ON, 52 HUGE_PAGES_TRY 53 } HugePagesType; 54 55 #ifndef WIN32 56 extern unsigned long UsedShmemSegID; 57 #else 58 extern HANDLE UsedShmemSegID; 59 extern void *ShmemProtectiveRegion; 60 #endif 61 extern void *UsedShmemSegAddr; 62 63 #ifdef EXEC_BACKEND 64 extern void PGSharedMemoryReAttach(void); 65 extern void PGSharedMemoryNoReAttach(void); 66 #endif 67 68 extern PGShmemHeader *PGSharedMemoryCreate(Size size, int port, 69 PGShmemHeader **shim); 70 extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2); 71 extern void PGSharedMemoryDetach(void); 72 73 #endif /* PG_SHMEM_H */ 74