1/*-------------------------------------------------------------------------
2 *
3 * dsa.h
4 * Dynamic shared memory areas.
5 *
6 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
8 *
9 * IDENTIFICATION
10 * src/include/utils/dsa.h
11 *
12 *-------------------------------------------------------------------------
13 */
14#ifndef DSA_H
15#define DSA_H
16
17#include "port/atomics.h"
18#include "storage/dsm.h"
19
20/* The opaque type used for an area. */
21struct dsa_area;
22typedef struct dsa_area dsa_area;
23
24/*
25 * If this system only uses a 32-bit value for size_t, then use the 32-bit
26 * implementation of DSA. This limits the amount of DSA that can be created
27 * to something significantly less than the entire 4GB address space because
28 * the DSA pointer must encode both a segment identifier and an offset, but
29 * that shouldn't be a significant limitation in practice.
30 *
31 * If this system doesn't support atomic operations on 64-bit values, then
32 * we fall back to 32-bit dsa_pointer for lack of other options.
33 *
34 * For testing purposes, USE_SMALL_DSA_POINTER can be defined to force the use
35 * of 32-bit dsa_pointer even on systems capable of supporting a 64-bit
36 * dsa_pointer.
37 */
38#if SIZEOF_SIZE_T == 4 || !defined(PG_HAVE_ATOMIC_U64_SUPPORT) || \
39 defined(USE_SMALL_DSA_POINTER)
40#define SIZEOF_DSA_POINTER 4
41#else
42#define SIZEOF_DSA_POINTER 8
43#endif
44
45/*
46 * The type of 'relative pointers' to memory allocated by a dynamic shared
47 * area. dsa_pointer values can be shared with other processes, but must be
48 * converted to backend-local pointers before they can be dereferenced. See
49 * dsa_get_address. Also, an atomic version and appropriately sized atomic
50 * operations.
51 */
52#if SIZEOF_DSA_POINTER == 4
53typedef uint32 dsa_pointer;
54typedef pg_atomic_uint32 dsa_pointer_atomic;
55#define dsa_pointer_atomic_init pg_atomic_init_u32
56#define dsa_pointer_atomic_read pg_atomic_read_u32
57#define dsa_pointer_atomic_write pg_atomic_write_u32
58#define dsa_pointer_atomic_fetch_add pg_atomic_fetch_add_u32
59#define dsa_pointer_atomic_compare_exchange pg_atomic_compare_exchange_u32
60#define DSA_POINTER_FORMAT "%08x"
61#else
62typedef uint64 dsa_pointer;
63typedef pg_atomic_uint64 dsa_pointer_atomic;
64#define dsa_pointer_atomic_init pg_atomic_init_u64
65#define dsa_pointer_atomic_read pg_atomic_read_u64
66#define dsa_pointer_atomic_write pg_atomic_write_u64
67#define dsa_pointer_atomic_fetch_add pg_atomic_fetch_add_u64
68#define dsa_pointer_atomic_compare_exchange pg_atomic_compare_exchange_u64
69#define DSA_POINTER_FORMAT "%016" INT64_MODIFIER "x"
70#endif
71
72/* Flags for dsa_allocate_extended. */
73#define DSA_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
74#define DSA_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
75#define DSA_ALLOC_ZERO 0x04 /* zero allocated memory */
76
77/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
78#define InvalidDsaPointer ((dsa_pointer) 0)
79
80/* Check if a dsa_pointer value is valid. */
81#define DsaPointerIsValid(x) ((x) != InvalidDsaPointer)
82
83/* Allocate uninitialized memory with error on out-of-memory. */
84#define dsa_allocate(area, size) \
85 dsa_allocate_extended(area, size, 0)
86
87/* Allocate zero-initialized memory with error on out-of-memory. */
88#define dsa_allocate0(area, size) \
89 dsa_allocate_extended(area, size, DSA_ALLOC_ZERO)
90
91/*
92 * The type used for dsa_area handles. dsa_handle values can be shared with
93 * other processes, so that they can attach to them. This provides a way to
94 * share allocated storage with other processes.
95 *
96 * The handle for a dsa_area is currently implemented as the dsm_handle
97 * for the first DSM segment backing this dynamic storage area, but client
98 * code shouldn't assume that is true.
99 */
100typedef dsm_handle dsa_handle;
101
102extern void dsa_startup(void);
103
104extern dsa_area *dsa_create(int tranche_id);
105extern dsa_area *dsa_create_in_place(void *place, size_t size,
106 int tranche_id, dsm_segment *segment);
107extern dsa_area *dsa_attach(dsa_handle handle);
108extern dsa_area *dsa_attach_in_place(void *place, dsm_segment *segment);
109extern void dsa_release_in_place(void *place);
110extern void dsa_on_dsm_detach_release_in_place(dsm_segment *, Datum);
111extern void dsa_on_shmem_exit_release_in_place(int, Datum);
112extern void dsa_pin_mapping(dsa_area *area);
113extern void dsa_detach(dsa_area *area);
114extern void dsa_pin(dsa_area *area);
115extern void dsa_unpin(dsa_area *area);
116extern void dsa_set_size_limit(dsa_area *area, size_t limit);
117extern size_t dsa_minimum_size(void);
118extern dsa_handle dsa_get_handle(dsa_area *area);
119extern dsa_pointer dsa_allocate_extended(dsa_area *area, size_t size, int flags);
120extern void dsa_free(dsa_area *area, dsa_pointer dp);
121extern void *dsa_get_address(dsa_area *area, dsa_pointer dp);
122extern void dsa_trim(dsa_area *area);
123extern void dsa_dump(dsa_area *area);
124
125#endif /* DSA_H */
126