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memnodes.h
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1 /*-------------------------------------------------------------------------
2  *
3  * memnodes.h
4  * POSTGRES memory context node definitions.
5  *
6  *
7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  * src/include/nodes/memnodes.h
11  *
12  *-------------------------------------------------------------------------
13  */
14 #ifndef MEMNODES_H
15 #define MEMNODES_H
16 
17 #include "nodes/nodes.h"
18 
19 /*
20  * MemoryContextCounters
21  * Summarization state for MemoryContextStats collection.
22  *
23  * The set of counters in this struct is biased towards AllocSet; if we ever
24  * add any context types that are based on fundamentally different approaches,
25  * we might need more or different counters here. A possible API spec then
26  * would be to print only nonzero counters, but for now we just summarize in
27  * the format historically used by AllocSet.
28  */
29 typedef struct MemoryContextCounters
30 {
31  Size nblocks; /* Total number of malloc blocks */
32  Size freechunks; /* Total number of free chunks */
33  Size totalspace; /* Total bytes requested from malloc */
34  Size freespace; /* The unused portion of totalspace */
36 
37 /*
38  * MemoryContext
39  * A logical context in which memory allocations occur.
40  *
41  * MemoryContext itself is an abstract type that can have multiple
42  * implementations.
43  * The function pointers in MemoryContextMethods define one specific
44  * implementation of MemoryContext --- they are a virtual function table
45  * in C++ terms.
46  *
47  * Node types that are actual implementations of memory contexts must
48  * begin with the same fields as MemoryContextData.
49  *
50  * Note: for largely historical reasons, typedef MemoryContext is a pointer
51  * to the context struct rather than the struct type itself.
52  */
53 
54 typedef void (*MemoryStatsPrintFunc) (MemoryContext context, void *passthru,
55  const char *stats_string,
56  bool print_to_stderr);
57 
58 typedef struct MemoryContextMethods
59 {
60  void *(*alloc) (MemoryContext context, Size size);
61  /* call this free_p in case someone #define's free() */
62  void (*free_p) (MemoryContext context, void *pointer);
63  void *(*realloc) (MemoryContext context, void *pointer, Size size);
64  void (*reset) (MemoryContext context);
65  void (*delete_context) (MemoryContext context);
66  Size (*get_chunk_space) (MemoryContext context, void *pointer);
67  bool (*is_empty) (MemoryContext context);
68  void (*stats) (MemoryContext context,
69  MemoryStatsPrintFunc printfunc, void *passthru,
70  MemoryContextCounters *totals,
71  bool print_to_stderr);
72 #ifdef MEMORY_CONTEXT_CHECKING
73  void (*check) (MemoryContext context);
74 #endif
76 
77 
78 typedef struct MemoryContextData
79 {
80  NodeTag type; /* identifies exact kind of context */
81  /* these two fields are placed here to minimize alignment wastage: */
82  bool isReset; /* T = no space alloced since last reset */
83  bool allowInCritSection; /* allow palloc in critical section */
84  Size mem_allocated; /* track memory allocated for this context */
85  const MemoryContextMethods *methods; /* virtual function table */
86  MemoryContext parent; /* NULL if no parent (toplevel context) */
87  MemoryContext firstchild; /* head of linked list of children */
88  MemoryContext prevchild; /* previous child of same parent */
89  MemoryContext nextchild; /* next child of same parent */
90  const char *name; /* context name (just for debugging) */
91  const char *ident; /* context ID if any (just for debugging) */
92  MemoryContextCallback *reset_cbs; /* list of reset/delete callbacks */
94 
95 /* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
96 
97 
98 /*
99  * MemoryContextIsValid
100  * True iff memory context is valid.
101  *
102  * Add new context types to the set accepted by this macro.
103  */
104 #define MemoryContextIsValid(context) \
105  ((context) != NULL && \
106  (IsA((context), AllocSetContext) || \
107  IsA((context), SlabContext) || \
108  IsA((context), GenerationContext)))
109 
110 #endif /* MEMNODES_H */
MemoryContextCallback * reset_cbs
Definition: memnodes.h:92
const MemoryContextMethods * methods
Definition: memnodes.h:85
void reset(void)
Definition: sql-declare.c:562
bool allowInCritSection
Definition: memnodes.h:83
void(* MemoryStatsPrintFunc)(MemoryContext context, void *passthru, const char *stats_string, bool print_to_stderr)
Definition: memnodes.h:54
NodeTag
Definition: nodes.h:26
struct MemoryContextMethods MemoryContextMethods
MemoryContext firstchild
Definition: memnodes.h:87
MemoryContext prevchild
Definition: memnodes.h:88
const char * ident
Definition: memnodes.h:91
size_t Size
Definition: c.h:540
Size mem_allocated
Definition: memnodes.h:84
struct MemoryContextCounters MemoryContextCounters
MemoryContext parent
Definition: memnodes.h:86
const char * name
Definition: memnodes.h:90
MemoryContext nextchild
Definition: memnodes.h:89
unsigned char bool
Definition: c.h:391
struct MemoryContextData MemoryContextData
NodeTag type
Definition: memnodes.h:80