54 lines
1.7 KiB
C
54 lines
1.7 KiB
C
/* Copyright 2016 IBM Corp.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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* implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Simple power-of-two buddy allocation mechanism.
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*
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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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