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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) 1996-2024, 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  /*
61  * Function to handle memory allocation requests of 'size' to allocate
62  * memory into the given 'context'. The function must handle flags
63  * MCXT_ALLOC_HUGE and MCXT_ALLOC_NO_OOM. MCXT_ALLOC_ZERO is handled by
64  * the calling function.
65  */
66  void *(*alloc) (MemoryContext context, Size size, int flags);
67 
68  /* call this free_p in case someone #define's free() */
69  void (*free_p) (void *pointer);
70 
71  /*
72  * Function to handle a size change request for an existing allocation.
73  * The implementation must handle flags MCXT_ALLOC_HUGE and
74  * MCXT_ALLOC_NO_OOM. MCXT_ALLOC_ZERO is handled by the calling function.
75  */
76  void *(*realloc) (void *pointer, Size size, int flags);
77 
78  /*
79  * Invalidate all previous allocations in the given memory context and
80  * prepare the context for a new set of allocations. Implementations may
81  * optionally free() excess memory back to the OS during this time.
82  */
84 
85  /* Free all memory consumed by the given MemoryContext. */
87 
88  /* Return the MemoryContext that the given pointer belongs to. */
89  MemoryContext (*get_chunk_context) (void *pointer);
90 
91  /*
92  * Return the number of bytes consumed by the given pointer within its
93  * memory context, including the overhead of alignment and chunk headers.
94  */
95  Size (*get_chunk_space) (void *pointer);
96 
97  /*
98  * Return true if the given MemoryContext has not had any allocations
99  * since it was created or last reset.
100  */
103  MemoryStatsPrintFunc printfunc, void *passthru,
104  MemoryContextCounters *totals,
105  bool print_to_stderr);
106 #ifdef MEMORY_CONTEXT_CHECKING
107 
108  /*
109  * Perform validation checks on the given context and raise any discovered
110  * anomalies as WARNINGs.
111  */
112  void (*check) (MemoryContext context);
113 #endif
115 
116 
117 typedef struct MemoryContextData
118 {
119  pg_node_attr(abstract) /* there are no nodes of this type */
120 
121  NodeTag type; /* identifies exact kind of context */
122  /* these two fields are placed here to minimize alignment wastage: */
123  bool isReset; /* T = no space alloced since last reset */
124  bool allowInCritSection; /* allow palloc in critical section */
125  Size mem_allocated; /* track memory allocated for this context */
126  const MemoryContextMethods *methods; /* virtual function table */
127  MemoryContext parent; /* NULL if no parent (toplevel context) */
128  MemoryContext firstchild; /* head of linked list of children */
129  MemoryContext prevchild; /* previous child of same parent */
130  MemoryContext nextchild; /* next child of same parent */
131  const char *name; /* context name (just for debugging) */
132  const char *ident; /* context ID if any (just for debugging) */
133  MemoryContextCallback *reset_cbs; /* list of reset/delete callbacks */
135 
136 /* utils/palloc.h contains typedef struct MemoryContextData *MemoryContext */
137 
138 
139 /*
140  * MemoryContextIsValid
141  * True iff memory context is valid.
142  *
143  * Add new context types to the set accepted by this macro.
144  */
145 #define MemoryContextIsValid(context) \
146  ((context) != NULL && \
147  (IsA((context), AllocSetContext) || \
148  IsA((context), SlabContext) || \
149  IsA((context), GenerationContext) || \
150  IsA((context), BumpContext)))
151 
152 #endif /* MEMNODES_H */
unsigned char bool
Definition: c.h:456
size_t Size
Definition: c.h:605
void(* MemoryStatsPrintFunc)(MemoryContext context, void *passthru, const char *stats_string, bool print_to_stderr)
Definition: memnodes.h:54
struct MemoryContextMethods MemoryContextMethods
struct MemoryContextCounters MemoryContextCounters
NodeTag
Definition: nodes.h:27
struct MemoryContextData * MemoryContext
Definition: palloc.h:36
tree context
Definition: radixtree.h:1835
static pg_noinline void Size size
Definition: slab.c:607
MemoryContext prevchild
Definition: memnodes.h:129
MemoryContext firstchild
Definition: memnodes.h:128
bool allowInCritSection
Definition: memnodes.h:124
const char * ident
Definition: memnodes.h:132
MemoryContext parent
Definition: memnodes.h:127
MemoryContextCallback * reset_cbs
Definition: memnodes.h:133
const MemoryContextMethods * methods
Definition: memnodes.h:126
MemoryContext nextchild
Definition: memnodes.h:130
pg_node_attr(abstract) NodeTag type
const char * name
Definition: memnodes.h:131
void(* delete_context)(MemoryContext context)
Definition: memnodes.h:86
void(* stats)(MemoryContext context, MemoryStatsPrintFunc printfunc, void *passthru, MemoryContextCounters *totals, bool print_to_stderr)
Definition: memnodes.h:102
void(* free_p)(void *pointer)
Definition: memnodes.h:69
bool(* is_empty)(MemoryContext context)
Definition: memnodes.h:101
void(* reset)(MemoryContext context)
Definition: memnodes.h:83
MemoryContext(* get_chunk_context)(void *pointer)
Definition: memnodes.h:89
Size(* get_chunk_space)(void *pointer)
Definition: memnodes.h:95
const char * type