codekingpro/portable-devtools

1/*-------------------------------------------------------------------------2 *3 * freepage.h4 *	  Management of page-organized free memory.5 *6 * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group7 * Portions Copyright (c) 1994, Regents of the University of California8 *9 * src/include/utils/freepage.h10 *11 *-------------------------------------------------------------------------12 */13 14#ifndef FREEPAGE_H15#define FREEPAGE_H16 17#include "storage/lwlock.h"18#include "utils/relptr.h"19 20/* Forward declarations. */21typedef struct FreePageSpanLeader FreePageSpanLeader;22typedef struct FreePageBtree FreePageBtree;23typedef struct FreePageManager FreePageManager;24 25/*26 * PostgreSQL normally uses 8kB pages for most things, but many common27 * architecture/operating system pairings use a 4kB page size for memory28 * allocation, so we do that here also.29 */30#define FPM_PAGE_SIZE			409631 32/*33 * Each freelist except for the last contains only spans of one particular34 * size.  Everything larger goes on the last one.  In some sense this seems35 * like a waste since most allocations are in a few common sizes, but it36 * means that small allocations can simply pop the head of the relevant list37 * without needing to worry about whether the object we find there is of38 * precisely the correct size (because we know it must be).39 */40#define FPM_NUM_FREELISTS		12941 42/* Define relative pointer types. */43relptr_declare(FreePageBtree, RelptrFreePageBtree);44relptr_declare(FreePageManager, RelptrFreePageManager);45relptr_declare(FreePageSpanLeader, RelptrFreePageSpanLeader);46 47/* Everything we need in order to manage free pages (see freepage.c) */48struct FreePageManager49{50	RelptrFreePageManager self;51	RelptrFreePageBtree btree_root;52	RelptrFreePageSpanLeader btree_recycle;53	unsigned	btree_depth;54	unsigned	btree_recycle_count;55	Size		singleton_first_page;56	Size		singleton_npages;57	Size		contiguous_pages;58	bool		contiguous_pages_dirty;59	RelptrFreePageSpanLeader freelist[FPM_NUM_FREELISTS];60#ifdef FPM_EXTRA_ASSERTS61	/* For debugging only, pages put minus pages gotten. */62	Size		free_pages;63#endif64};65 66/* Macros to convert between page numbers (expressed as Size) and pointers. */67#define fpm_page_to_pointer(base, page) \68	(AssertVariableIsOfTypeMacro(page, Size), \69	 (base) + FPM_PAGE_SIZE * (page))70#define fpm_pointer_to_page(base, ptr)		\71	(((Size) (((char *) (ptr)) - (base))) / FPM_PAGE_SIZE)72 73/* Macro to convert an allocation size to a number of pages. */74#define fpm_size_to_pages(sz) \75	(((sz) + FPM_PAGE_SIZE - 1) / FPM_PAGE_SIZE)76 77/* Macros to check alignment of absolute and relative pointers. */78#define fpm_pointer_is_page_aligned(base, ptr)		\79	(((Size) (((char *) (ptr)) - (base))) % FPM_PAGE_SIZE == 0)80#define fpm_relptr_is_page_aligned(base, relptr)		\81	(relptr_offset(relptr) % FPM_PAGE_SIZE == 0)82 83/* Macro to find base address of the segment containing a FreePageManager. */84#define fpm_segment_base(fpm)	\85	(((char *) fpm) - relptr_offset(fpm->self))86 87/* Macro to access a FreePageManager's largest consecutive run of pages. */88#define fpm_largest(fpm) \89	(fpm->contiguous_pages)90 91/* Functions to manipulate the free page map. */92extern void FreePageManagerInitialize(FreePageManager *fpm, char *base);93extern bool FreePageManagerGet(FreePageManager *fpm, Size npages,94							   Size *first_page);95extern void FreePageManagerPut(FreePageManager *fpm, Size first_page,96							   Size npages);97extern char *FreePageManagerDump(FreePageManager *fpm);98 99#endif							/* FREEPAGE_H */100