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dsa.h
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dsa.h
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/*-------------------------------------------------------------------------
*
* dsa.h
* Dynamic shared memory areas.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/include/utils/dsa.h
*
*-------------------------------------------------------------------------
*/
#ifndef DSA_H
#define DSA_H
#include "port/atomics.h"
#include "storage/dsm.h"
/* The opaque type used for an area. */
struct dsa_area;
typedef struct dsa_area dsa_area;
/*
* If this system only uses a 32-bit value for size_t, then use the 32-bit
* implementation of DSA. This limits the amount of DSA that can be created
* to something significantly less than the entire 4GB address space because
* the DSA pointer must encode both a segment identifier and an offset, but
* that shouldn't be a significant limitation in practice.
*
* If this system doesn't support atomic operations on 64-bit values, then
* we fall back to 32-bit dsa_pointer for lack of other options.
*
* For testing purposes, USE_SMALL_DSA_POINTER can be defined to force the use
* of 32-bit dsa_pointer even on systems capable of supporting a 64-bit
* dsa_pointer.
*/
#if SIZEOF_SIZE_T == 4 || !defined(PG_HAVE_ATOMIC_U64_SUPPORT) || \
defined(USE_SMALL_DSA_POINTER)
#define SIZEOF_DSA_POINTER 4
#else
#define SIZEOF_DSA_POINTER 8
#endif
/*
* The type of 'relative pointers' to memory allocated by a dynamic shared
* area. dsa_pointer values can be shared with other processes, but must be
* converted to backend-local pointers before they can be dereferenced. See
* dsa_get_address. Also, an atomic version and appropriately sized atomic
* operations.
*/
#if SIZEOF_DSA_POINTER == 4
typedef uint32 dsa_pointer;
typedef pg_atomic_uint32 dsa_pointer_atomic;
#define dsa_pointer_atomic_init pg_atomic_init_u32
#define dsa_pointer_atomic_read pg_atomic_read_u32
#define dsa_pointer_atomic_write pg_atomic_write_u32
#define dsa_pointer_atomic_fetch_add pg_atomic_fetch_add_u32
#define dsa_pointer_atomic_compare_exchange pg_atomic_compare_exchange_u32
#define DSA_POINTER_FORMAT "%08x"
#else
typedef uint64 dsa_pointer;
typedef pg_atomic_uint64 dsa_pointer_atomic;
#define dsa_pointer_atomic_init pg_atomic_init_u64
#define dsa_pointer_atomic_read pg_atomic_read_u64
#define dsa_pointer_atomic_write pg_atomic_write_u64
#define dsa_pointer_atomic_fetch_add pg_atomic_fetch_add_u64
#define dsa_pointer_atomic_compare_exchange pg_atomic_compare_exchange_u64
#define DSA_POINTER_FORMAT "%016" INT64_MODIFIER "x"
#endif
/* Flags for dsa_allocate_extended. */
#define DSA_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
#define DSA_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
#define DSA_ALLOC_ZERO 0x04 /* zero allocated memory */
/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
#define InvalidDsaPointer ((dsa_pointer) 0)
/* Check if a dsa_pointer value is valid. */
#define DsaPointerIsValid(x) ((x) != InvalidDsaPointer)
/* Allocate uninitialized memory with error on out-of-memory. */
#define dsa_allocate(area, size) \
dsa_allocate_extended(area, size, 0)
/* Allocate zero-initialized memory with error on out-of-memory. */
#define dsa_allocate0(area, size) \
dsa_allocate_extended(area, size, DSA_ALLOC_ZERO)
/*
* The type used for dsa_area handles. dsa_handle values can be shared with
* other processes, so that they can attach to them. This provides a way to
* share allocated storage with other processes.
*
* The handle for a dsa_area is currently implemented as the dsm_handle
* for the first DSM segment backing this dynamic storage area, but client
* code shouldn't assume that is true.
*/
typedef dsm_handle dsa_handle;
extern void dsa_startup(void);
extern dsa_area *dsa_create(int tranche_id);
extern dsa_area *dsa_create_in_place(void *place, size_t size,
int tranche_id, dsm_segment *segment);
extern dsa_area *dsa_attach(dsa_handle handle);
extern dsa_area *dsa_attach_in_place(void *place, dsm_segment *segment);
extern void dsa_release_in_place(void *place);
extern void dsa_on_dsm_detach_release_in_place(dsm_segment *, Datum);
extern void dsa_on_shmem_exit_release_in_place(int, Datum);
extern void dsa_pin_mapping(dsa_area *area);
extern void dsa_detach(dsa_area *area);
extern void dsa_pin(dsa_area *area);
extern void dsa_unpin(dsa_area *area);
extern void dsa_set_size_limit(dsa_area *area, size_t limit);
extern size_t dsa_minimum_size(void);
extern dsa_handle dsa_get_handle(dsa_area *area);
extern dsa_pointer dsa_allocate_extended(dsa_area *area, size_t size, int flags);
extern void dsa_free(dsa_area *area, dsa_pointer dp);
extern void *dsa_get_address(dsa_area *area, dsa_pointer dp);
extern void dsa_trim(dsa_area *area);
extern void dsa_dump(dsa_area *area);
#endif /* DSA_H */