100 lines
3.4 KiB
C
100 lines
3.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* freepage.h
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* Management of page-organized free memory.
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*
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* Portions Copyright (c) 1996-2024, 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/freepage.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef FREEPAGE_H
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#define FREEPAGE_H
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#include "storage/lwlock.h"
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#include "utils/relptr.h"
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/* Forward declarations. */
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typedef struct FreePageSpanLeader FreePageSpanLeader;
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typedef struct FreePageBtree FreePageBtree;
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typedef struct FreePageManager FreePageManager;
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/*
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* PostgreSQL normally uses 8kB pages for most things, but many common
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* architecture/operating system pairings use a 4kB page size for memory
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* allocation, so we do that here also.
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*/
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#define FPM_PAGE_SIZE 4096
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/*
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* Each freelist except for the last contains only spans of one particular
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* size. Everything larger goes on the last one. In some sense this seems
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* like a waste since most allocations are in a few common sizes, but it
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* means that small allocations can simply pop the head of the relevant list
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* without needing to worry about whether the object we find there is of
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* precisely the correct size (because we know it must be).
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*/
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#define FPM_NUM_FREELISTS 129
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/* Define relative pointer types. */
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relptr_declare(FreePageBtree, RelptrFreePageBtree);
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relptr_declare(FreePageManager, RelptrFreePageManager);
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relptr_declare(FreePageSpanLeader, RelptrFreePageSpanLeader);
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/* Everything we need in order to manage free pages (see freepage.c) */
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struct FreePageManager
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{
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RelptrFreePageManager self;
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RelptrFreePageBtree btree_root;
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RelptrFreePageSpanLeader btree_recycle;
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unsigned btree_depth;
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unsigned btree_recycle_count;
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Size singleton_first_page;
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Size singleton_npages;
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Size contiguous_pages;
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bool contiguous_pages_dirty;
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RelptrFreePageSpanLeader freelist[FPM_NUM_FREELISTS];
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#ifdef FPM_EXTRA_ASSERTS
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/* For debugging only, pages put minus pages gotten. */
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Size free_pages;
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#endif
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};
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/* Macros to convert between page numbers (expressed as Size) and pointers. */
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#define fpm_page_to_pointer(base, page) \
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(AssertVariableIsOfTypeMacro(page, Size), \
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(base) + FPM_PAGE_SIZE * (page))
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#define fpm_pointer_to_page(base, ptr) \
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(((Size) (((char *) (ptr)) - (base))) / FPM_PAGE_SIZE)
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/* Macro to convert an allocation size to a number of pages. */
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#define fpm_size_to_pages(sz) \
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(((sz) + FPM_PAGE_SIZE - 1) / FPM_PAGE_SIZE)
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/* Macros to check alignment of absolute and relative pointers. */
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#define fpm_pointer_is_page_aligned(base, ptr) \
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(((Size) (((char *) (ptr)) - (base))) % FPM_PAGE_SIZE == 0)
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#define fpm_relptr_is_page_aligned(base, relptr) \
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(relptr_offset(relptr) % FPM_PAGE_SIZE == 0)
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/* Macro to find base address of the segment containing a FreePageManager. */
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#define fpm_segment_base(fpm) \
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(((char *) fpm) - relptr_offset(fpm->self))
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/* Macro to access a FreePageManager's largest consecutive run of pages. */
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#define fpm_largest(fpm) \
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(fpm->contiguous_pages)
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/* Functions to manipulate the free page map. */
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extern void FreePageManagerInitialize(FreePageManager *fpm, char *base);
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extern bool FreePageManagerGet(FreePageManager *fpm, Size npages,
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Size *first_page);
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extern void FreePageManagerPut(FreePageManager *fpm, Size first_page,
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Size npages);
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extern char *FreePageManagerDump(FreePageManager *fpm);
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#endif /* FREEPAGE_H */
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