151 lines
5.3 KiB
C
151 lines
5.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* memutils.h
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* This file contains declarations for memory allocation utility
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* functions. These are functions that are not quite widely used
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* enough to justify going in utils/palloc.h, but are still part
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* of the API of the memory management subsystem.
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*
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*
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* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/memutils.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef MEMUTILS_H
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#define MEMUTILS_H
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#include "nodes/memnodes.h"
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/*
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* MaxAllocSize, MaxAllocHugeSize
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* Quasi-arbitrary limits on size of allocations.
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*
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* Note:
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* There is no guarantee that smaller allocations will succeed, but
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* larger requests will be summarily denied.
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*
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* palloc() enforces MaxAllocSize, chosen to correspond to the limiting size
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* of varlena objects under TOAST. See VARSIZE_4B() and related macros in
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* postgres.h. Many datatypes assume that any allocatable size can be
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* represented in a varlena header. This limit also permits a caller to use
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* an "int" variable for an index into or length of an allocation. Callers
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* careful to avoid these hazards can access the higher limit with
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* MemoryContextAllocHuge(). Both limits permit code to assume that it may
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* compute twice an allocation's size without overflow.
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*/
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#define MaxAllocSize ((Size) 0x3fffffff) /* 1 gigabyte - 1 */
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#define AllocSizeIsValid(size) ((Size) (size) <= MaxAllocSize)
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#define MaxAllocHugeSize ((Size) -1 >> 1) /* SIZE_MAX / 2 */
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#define AllocHugeSizeIsValid(size) ((Size) (size) <= MaxAllocHugeSize)
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/*
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* All chunks allocated by any memory context manager are required to be
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* preceded by a StandardChunkHeader at a spacing of STANDARDCHUNKHEADERSIZE.
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* A currently-allocated chunk must contain a backpointer to its owning
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* context as well as the allocated size of the chunk. The backpointer is
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* used by pfree() and repalloc() to find the context to call. The allocated
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* size is not absolutely essential, but it's expected to be needed by any
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* reasonable implementation.
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*/
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typedef struct StandardChunkHeader
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{
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MemoryContext context; /* owning context */
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Size size; /* size of data space allocated in chunk */
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#ifdef MEMORY_CONTEXT_CHECKING
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/* when debugging memory usage, also store actual requested size */
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Size requested_size;
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#endif
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} StandardChunkHeader;
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#define STANDARDCHUNKHEADERSIZE MAXALIGN(sizeof(StandardChunkHeader))
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/*
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* Standard top-level memory contexts.
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*
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* Only TopMemoryContext and ErrorContext are initialized by
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* MemoryContextInit() itself.
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*/
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extern PGDLLIMPORT MemoryContext TopMemoryContext;
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extern PGDLLIMPORT MemoryContext ErrorContext;
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extern PGDLLIMPORT MemoryContext PostmasterContext;
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extern PGDLLIMPORT MemoryContext CacheMemoryContext;
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extern PGDLLIMPORT MemoryContext MessageContext;
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extern PGDLLIMPORT MemoryContext TopTransactionContext;
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extern PGDLLIMPORT MemoryContext CurTransactionContext;
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/* This is a transient link to the active portal's memory context: */
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extern PGDLLIMPORT MemoryContext PortalContext;
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/*
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* Memory-context-type-independent functions in mcxt.c
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*/
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extern void MemoryContextInit(void);
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extern void MemoryContextReset(MemoryContext context);
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extern void MemoryContextDelete(MemoryContext context);
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extern void MemoryContextResetChildren(MemoryContext context);
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extern void MemoryContextDeleteChildren(MemoryContext context);
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extern void MemoryContextResetAndDeleteChildren(MemoryContext context);
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extern void MemoryContextSetParent(MemoryContext context,
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MemoryContext new_parent);
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extern Size GetMemoryChunkSpace(void *pointer);
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extern MemoryContext GetMemoryChunkContext(void *pointer);
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extern MemoryContext MemoryContextGetParent(MemoryContext context);
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extern bool MemoryContextIsEmpty(MemoryContext context);
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extern void MemoryContextStats(MemoryContext context);
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extern void MemoryContextAllowInCriticalSection(MemoryContext context,
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bool allow);
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#ifdef MEMORY_CONTEXT_CHECKING
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extern void MemoryContextCheck(MemoryContext context);
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#endif
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extern bool MemoryContextContains(MemoryContext context, void *pointer);
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/*
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* This routine handles the context-type-independent part of memory
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* context creation. It's intended to be called from context-type-
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* specific creation routines, and noplace else.
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*/
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extern MemoryContext MemoryContextCreate(NodeTag tag, Size size,
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MemoryContextMethods *methods,
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MemoryContext parent,
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const char *name);
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/*
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* Memory-context-type-specific functions
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*/
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/* aset.c */
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extern MemoryContext AllocSetContextCreate(MemoryContext parent,
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const char *name,
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Size minContextSize,
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Size initBlockSize,
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Size maxBlockSize);
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/*
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* Recommended default alloc parameters, suitable for "ordinary" contexts
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* that might hold quite a lot of data.
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*/
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#define ALLOCSET_DEFAULT_MINSIZE 0
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#define ALLOCSET_DEFAULT_INITSIZE (8 * 1024)
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#define ALLOCSET_DEFAULT_MAXSIZE (8 * 1024 * 1024)
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/*
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* Recommended alloc parameters for "small" contexts that are not expected
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* to contain much data (for example, a context to contain a query plan).
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*/
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#define ALLOCSET_SMALL_MINSIZE 0
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#define ALLOCSET_SMALL_INITSIZE (1 * 1024)
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#define ALLOCSET_SMALL_MAXSIZE (8 * 1024)
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#endif /* MEMUTILS_H */
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