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memutils.h
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1 /*-------------------------------------------------------------------------
2  *
3  * memutils.h
4  * This file contains declarations for memory allocation utility
5  * functions. These are functions that are not quite widely used
6  * enough to justify going in utils/palloc.h, but are still part
7  * of the API of the memory management subsystem.
8  *
9  *
10  * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
11  * Portions Copyright (c) 1994, Regents of the University of California
12  *
13  * src/include/utils/memutils.h
14  *
15  *-------------------------------------------------------------------------
16  */
17 #ifndef MEMUTILS_H
18 #define MEMUTILS_H
19 
20 #include "nodes/memnodes.h"
21 
22 
23 /*
24  * MaxAllocSize, MaxAllocHugeSize
25  * Quasi-arbitrary limits on size of allocations.
26  *
27  * Note:
28  * There is no guarantee that smaller allocations will succeed, but
29  * larger requests will be summarily denied.
30  *
31  * palloc() enforces MaxAllocSize, chosen to correspond to the limiting size
32  * of varlena objects under TOAST. See VARSIZE_4B() and related macros in
33  * postgres.h. Many datatypes assume that any allocatable size can be
34  * represented in a varlena header. This limit also permits a caller to use
35  * an "int" variable for an index into or length of an allocation. Callers
36  * careful to avoid these hazards can access the higher limit with
37  * MemoryContextAllocHuge(). Both limits permit code to assume that it may
38  * compute twice an allocation's size without overflow.
39  */
40 #define MaxAllocSize ((Size) 0x3fffffff) /* 1 gigabyte - 1 */
41 
42 #define AllocSizeIsValid(size) ((Size) (size) <= MaxAllocSize)
43 
44 #define MaxAllocHugeSize (SIZE_MAX / 2)
45 
46 #define AllocHugeSizeIsValid(size) ((Size) (size) <= MaxAllocHugeSize)
47 
48 
49 /*
50  * Standard top-level memory contexts.
51  *
52  * Only TopMemoryContext and ErrorContext are initialized by
53  * MemoryContextInit() itself.
54  */
62 
63 /* This is a transient link to the active portal's memory context: */
65 
66 /* Backwards compatibility macro */
67 #define MemoryContextResetAndDeleteChildren(ctx) MemoryContextReset(ctx)
68 
69 
70 /*
71  * Memory-context-type-independent functions in mcxt.c
72  */
73 extern void MemoryContextInit(void);
74 extern void MemoryContextReset(MemoryContext context);
75 extern void MemoryContextDelete(MemoryContext context);
76 extern void MemoryContextResetOnly(MemoryContext context);
77 extern void MemoryContextResetChildren(MemoryContext context);
78 extern void MemoryContextDeleteChildren(MemoryContext context);
79 extern void MemoryContextSetIdentifier(MemoryContext context, const char *id);
80 extern void MemoryContextSetParent(MemoryContext context,
81  MemoryContext new_parent);
82 extern Size GetMemoryChunkSpace(void *pointer);
84 extern bool MemoryContextIsEmpty(MemoryContext context);
85 extern void MemoryContextStats(MemoryContext context);
86 extern void MemoryContextStatsDetail(MemoryContext context, int max_children);
88  bool allow);
89 
90 #ifdef MEMORY_CONTEXT_CHECKING
91 extern void MemoryContextCheck(MemoryContext context);
92 #endif
93 extern bool MemoryContextContains(MemoryContext context, void *pointer);
94 
95 /* Handy macro for copying and assigning context ID ... but note double eval */
96 #define MemoryContextCopyAndSetIdentifier(cxt, id) \
97  MemoryContextSetIdentifier(cxt, MemoryContextStrdup(cxt, id))
98 
99 /*
100  * GetMemoryChunkContext
101  * Given a currently-allocated chunk, determine the context
102  * it belongs to.
103  *
104  * All chunks allocated by any memory context manager are required to be
105  * preceded by the corresponding MemoryContext stored, without padding, in the
106  * preceding sizeof(void*) bytes. A currently-allocated chunk must contain a
107  * backpointer to its owning context. The backpointer is used by pfree() and
108  * repalloc() to find the context to call.
109  */
110 #ifndef FRONTEND
111 static inline MemoryContext
112 GetMemoryChunkContext(void *pointer)
113 {
114  MemoryContext context;
115 
116  /*
117  * Try to detect bogus pointers handed to us, poorly though we can.
118  * Presumably, a pointer that isn't MAXALIGNED isn't pointing at an
119  * allocated chunk.
120  */
121  Assert(pointer != NULL);
122  Assert(pointer == (void *) MAXALIGN(pointer));
123 
124  /*
125  * OK, it's probably safe to look at the context.
126  */
127  context = *(MemoryContext *) (((char *) pointer) - sizeof(void *));
128 
130 
131  return context;
132 }
133 #endif
134 
135 /*
136  * This routine handles the context-type-independent part of memory
137  * context creation. It's intended to be called from context-type-
138  * specific creation routines, and noplace else.
139  */
140 extern void MemoryContextCreate(MemoryContext node,
141  NodeTag tag,
142  const MemoryContextMethods *methods,
143  MemoryContext parent,
144  const char *name);
145 
146 
147 /*
148  * Memory-context-type-specific functions
149  */
150 
151 /* aset.c */
153  const char *name,
154  Size minContextSize,
155  Size initBlockSize,
156  Size maxBlockSize);
157 
158 /*
159  * This wrapper macro exists to check for non-constant strings used as context
160  * names; that's no longer supported. (Use MemoryContextSetIdentifier if you
161  * want to provide a variable identifier.) Note you must specify block sizes
162  * with one of the abstraction macros below.
163  */
164 #ifdef HAVE__BUILTIN_CONSTANT_P
165 #define AllocSetContextCreate(parent, name, allocparams) \
166  (StaticAssertExpr(__builtin_constant_p(name), \
167  "memory context names must be constant strings"), \
168  AllocSetContextCreateExtended(parent, name, allocparams))
169 #else
170 #define AllocSetContextCreate(parent, name, allocparams) \
171  AllocSetContextCreateExtended(parent, name, allocparams)
172 #endif
173 
174 /* slab.c */
176  const char *name,
177  Size blockSize,
178  Size chunkSize);
179 
180 /* generation.c */
182  const char *name,
183  Size blockSize);
184 
185 /*
186  * Recommended default alloc parameters, suitable for "ordinary" contexts
187  * that might hold quite a lot of data.
188  */
189 #define ALLOCSET_DEFAULT_MINSIZE 0
190 #define ALLOCSET_DEFAULT_INITSIZE (8 * 1024)
191 #define ALLOCSET_DEFAULT_MAXSIZE (8 * 1024 * 1024)
192 #define ALLOCSET_DEFAULT_SIZES \
193  ALLOCSET_DEFAULT_MINSIZE, ALLOCSET_DEFAULT_INITSIZE, ALLOCSET_DEFAULT_MAXSIZE
194 
195 /*
196  * Recommended alloc parameters for "small" contexts that are never expected
197  * to contain much data (for example, a context to contain a query plan).
198  */
199 #define ALLOCSET_SMALL_MINSIZE 0
200 #define ALLOCSET_SMALL_INITSIZE (1 * 1024)
201 #define ALLOCSET_SMALL_MAXSIZE (8 * 1024)
202 #define ALLOCSET_SMALL_SIZES \
203  ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MAXSIZE
204 
205 /*
206  * Recommended alloc parameters for contexts that should start out small,
207  * but might sometimes grow big.
208  */
209 #define ALLOCSET_START_SMALL_SIZES \
210  ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE, ALLOCSET_DEFAULT_MAXSIZE
211 
212 
213 /*
214  * Threshold above which a request in an AllocSet context is certain to be
215  * allocated separately (and thereby have constant allocation overhead).
216  * Few callers should be interested in this, but tuplesort/tuplestore need
217  * to know it.
218  */
219 #define ALLOCSET_SEPARATE_THRESHOLD 8192
220 
221 #define SLAB_DEFAULT_BLOCK_SIZE (8 * 1024)
222 #define SLAB_LARGE_BLOCK_SIZE (8 * 1024 * 1024)
223 
224 #endif /* MEMUTILS_H */
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:211
PGDLLIMPORT MemoryContext CacheMemoryContext
Definition: mcxt.c:47
bool MemoryContextIsEmpty(MemoryContext context)
Definition: mcxt.c:451
void MemoryContextAllowInCriticalSection(MemoryContext context, bool allow)
Definition: mcxt.c:411
MemoryContext SlabContextCreate(MemoryContext parent, const char *name, Size blockSize, Size chunkSize)
Definition: slab.c:188
void MemoryContextDeleteChildren(MemoryContext context)
Definition: mcxt.c:256
void MemoryContextResetOnly(MemoryContext context)
Definition: mcxt.c:155
void MemoryContextReset(MemoryContext context)
Definition: mcxt.c:136
MemoryContext AllocSetContextCreateExtended(MemoryContext parent, const char *name, Size minContextSize, Size initBlockSize, Size maxBlockSize)
Definition: aset.c:388
PGDLLIMPORT MemoryContext PortalContext
Definition: mcxt.c:53
void MemoryContextSetIdentifier(MemoryContext context, const char *id)
Definition: mcxt.c:329
PGDLLIMPORT MemoryContext PostmasterContext
Definition: mcxt.c:46
NodeTag
Definition: nodes.h:26
#define PGDLLIMPORT
Definition: c.h:1105
bool MemoryContextContains(MemoryContext context, void *pointer)
Definition: mcxt.c:667
void MemoryContextStats(MemoryContext context)
Definition: mcxt.c:474
PGDLLIMPORT MemoryContext TopTransactionContext
Definition: mcxt.c:49
PGDLLIMPORT MemoryContext MessageContext
Definition: mcxt.c:48
MemoryContext MemoryContextGetParent(MemoryContext context)
Definition: mcxt.c:439
Size GetMemoryChunkSpace(void *pointer)
Definition: mcxt.c:427
void MemoryContextResetChildren(MemoryContext context)
Definition: mcxt.c:188
void MemoryContextCreate(MemoryContext node, NodeTag tag, const MemoryContextMethods *methods, MemoryContext parent, const char *name)
Definition: mcxt.c:724
#define AssertArg(condition)
Definition: c.h:701
MemoryContext GenerationContextCreate(MemoryContext parent, const char *name, Size blockSize)
Definition: generation.c:212
PGDLLIMPORT MemoryContext CurTransactionContext
Definition: mcxt.c:50
void MemoryContextStatsDetail(MemoryContext context, int max_children)
Definition: mcxt.c:486
#define MemoryContextIsValid(context)
Definition: memnodes.h:101
#define Assert(condition)
Definition: c.h:699
void MemoryContextSetParent(MemoryContext context, MemoryContext new_parent)
Definition: mcxt.c:354
size_t Size
Definition: c.h:433
#define MAXALIGN(LEN)
Definition: c.h:652
const char * name
Definition: encode.c:521
PGDLLIMPORT MemoryContext TopMemoryContext
Definition: mcxt.c:44
PGDLLIMPORT MemoryContext ErrorContext
Definition: mcxt.c:45
void MemoryContextInit(void)
Definition: mcxt.c:92
static MemoryContext GetMemoryChunkContext(void *pointer)
Definition: memutils.h:112