43 lines
1.2 KiB
C
43 lines
1.2 KiB
C
// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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/*
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* Simple power-of-two buddy allocation mechanism.
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*
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* Copyright 2016 IBM Corp.
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*/
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#ifndef __BUDDY_H
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#define __BUDDY_H
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#include "bitmap.h"
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#define BUDDY_MAX_ORDER 30
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struct buddy {
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/* max_order is both the height of the tree - 1 and the ^2 of the
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* size of the lowest level.
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*
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* So if we have 512k elements, max_order is 19, which gives us
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* a 20 levels tree.
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*
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* The max supported order is 30 for now. We can increase that
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* later if really needed but the performance is going to be
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* already pretty bad if we go near that limit.
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*/
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unsigned int max_order;
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/* For each order, we keep track of how many free modes we
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* have there to speed up searches.
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*/
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unsigned int freecounts[BUDDY_MAX_ORDER + 1];
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bitmap_elem_t map[];
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};
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extern struct buddy *buddy_create(unsigned int max_order);
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extern void buddy_destroy(struct buddy *b);
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extern int buddy_alloc(struct buddy *b, unsigned int order);
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extern bool buddy_reserve(struct buddy *b, unsigned int index, unsigned int order);
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extern void buddy_free(struct buddy *b, unsigned int index, unsigned int order);
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extern void buddy_reset(struct buddy *b);
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#endif /* __BUDDY_H */
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