source: mainline/kernel/generic/src/mm/buddy.c@ 62cd66f

/*
 * Copyright (c) 2005 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup genericmm
 * @{
 */

/**
 * @file
 * @brief       Buddy allocator framework.
 *
 * This file contains buddy system allocator framework.
 * Specialized functions are needed for this abstract framework
 * to be useful.
 */

#include <mm/buddy.h>
#include <mm/frame.h>
#include <arch/types.h>
#include <debug.h>
#include <print.h>
#include <macros.h>

/** Return size needed for the buddy configuration data */
size_t buddy_conf_size(int max_order)
{
        return sizeof(buddy_system_t) + (max_order + 1) * sizeof(link_t);
}


/** Create buddy system
 *
 * Allocate memory for and initialize new buddy system.
 *
 * @param b Preallocated buddy system control data.
 * @param max_order The biggest allocable size will be 2^max_order.
 * @param op Operations for new buddy system.
 * @param data Pointer to be used by implementation.
 *
 * @return New buddy system.
 */
void buddy_system_create(buddy_system_t *b,
                         uint8_t max_order, 
                         buddy_system_operations_t *op, 
                         void *data)
{
        int i;

        ASSERT(max_order < BUDDY_SYSTEM_INNER_BLOCK);

        ASSERT(op->find_buddy);
        ASSERT(op->set_order);
        ASSERT(op->get_order);
        ASSERT(op->bisect);
        ASSERT(op->coalesce);
        ASSERT(op->mark_busy);

        /*
         * Use memory after our own structure
         */
        b->order = (link_t *) (&b[1]);
        
        for (i = 0; i <= max_order; i++)
                list_initialize(&b->order[i]);

        b->max_order = max_order;
        b->op = op;
        b->data = data;
}

/** Check if buddy system can allocate block
 *
 * @param b Buddy system pointer
 * @param i Size of the block (2^i)
 *
 * @return True if block can be allocated
 */
bool buddy_system_can_alloc(buddy_system_t *b, uint8_t i) {
        uint8_t k;
        
        /*
         * If requested block is greater then maximal block
         * we know immediatly that we cannot satisfy the request.
         */
        if (i > b->max_order) return false;

        /*
         * Check if any bigger or equal order has free elements
         */
        for (k=i; k <= b->max_order; k++) {
                if (!list_empty(&b->order[k])) {
                        return true;
                }
        }
        
        return false;
        
}

/** Allocate PARTICULAR block from buddy system
 *
 * @ return Block of data or NULL if no such block was found
 */
link_t *buddy_system_alloc_block(buddy_system_t *b, link_t *block)
{
        link_t *left,*right, *tmp;
        uint8_t order;

        left = b->op->find_block(b, block, BUDDY_SYSTEM_INNER_BLOCK);
        ASSERT(left);
        list_remove(left);
        while (1) {
                if (! b->op->get_order(b,left)) {
                        b->op->mark_busy(b, left);
                        return left;
                }
                
                order = b->op->get_order(b, left);

                right = b->op->bisect(b, left);
                b->op->set_order(b, left, order-1);
                b->op->set_order(b, right, order-1);

                tmp = b->op->find_block(b, block, BUDDY_SYSTEM_INNER_BLOCK);

                if (tmp == right) {
                        right = left;
                        left = tmp;
                } 
                ASSERT(tmp == left);
                b->op->mark_busy(b, left);
                buddy_system_free(b, right);
                b->op->mark_available(b, left);
        }
}

/** Allocate block from buddy system.
 *
 * @param b Buddy system pointer.
 * @param i Returned block will be 2^i big.
 *
 * @return Block of data represented by link_t.
 */
link_t *buddy_system_alloc(buddy_system_t *b, uint8_t i)
{
        link_t *res, *hlp;

        ASSERT(i <= b->max_order);

        /*
         * If the list of order i is not empty,
         * the request can be immediatelly satisfied.
         */
        if (!list_empty(&b->order[i])) {
                res = b->order[i].next;
                list_remove(res);
                b->op->mark_busy(b, res);
                return res;
        }
        /*
         * If order i is already the maximal order,
         * the request cannot be satisfied.
         */
        if (i == b->max_order)
                return NULL;

        /*
         * Try to recursively satisfy the request from higher order lists.
         */     
        hlp = buddy_system_alloc(b, i + 1);
        
        /*
         * The request could not be satisfied
         * from higher order lists.
         */
        if (!hlp)
                return NULL;
                
        res = hlp;
        
        /*
         * Bisect the block and set order of both of its parts to i.
         */
        hlp = b->op->bisect(b, res);
        b->op->set_order(b, res, i);
        b->op->set_order(b, hlp, i);
        
        /*
         * Return the other half to buddy system. Mark the first part
         * full, so that it won't coalesce again.
         */
        b->op->mark_busy(b, res);
        buddy_system_free(b, hlp);
        
        return res;
        
}

/** Return block to buddy system.
 *
 * @param b Buddy system pointer.
 * @param block Block to return.
 */
void buddy_system_free(buddy_system_t *b, link_t *block)
{
        link_t *buddy, *hlp;
        uint8_t i;

        /*
         * Determine block's order.
         */
        i = b->op->get_order(b, block);

        ASSERT(i <= b->max_order);

        if (i != b->max_order) {
                /*
                 * See if there is any buddy in the list of order i.
                 */
                buddy = b->op->find_buddy(b, block);
                if (buddy) {

                        ASSERT(b->op->get_order(b, buddy) == i);
                        /*
                         * Remove buddy from the list of order i.
                         */
                        list_remove(buddy);
                
                        /*
                         * Invalidate order of both block and buddy.
                         */
                        b->op->set_order(b, block, BUDDY_SYSTEM_INNER_BLOCK);
                        b->op->set_order(b, buddy, BUDDY_SYSTEM_INNER_BLOCK);
                
                        /*
                         * Coalesce block and buddy into one block.
                         */
                        hlp = b->op->coalesce(b, block, buddy);

                        /*
                         * Set order of the coalesced block to i + 1.
                         */
                        b->op->set_order(b, hlp, i + 1);

                        /*
                         * Recursively add the coalesced block to the list of order i + 1.
                         */
                        buddy_system_free(b, hlp);
                        return;
                }
        }

        /*
         * Insert block into the list of order i.
         */
        list_append(block, &b->order[i]);

}

/** Prints out structure of buddy system
 *
 * @param b Pointer to buddy system
 * @param elem_size Element size
 */
void buddy_system_structure_print(buddy_system_t *b, size_t elem_size) {
        index_t i;
        count_t cnt, elem_count = 0, block_count = 0;
        link_t *cur;
        

        printf("Order\tBlocks\tSize    \tBlock size\tElems per block\n");
        printf("-----\t------\t--------\t----------\t---------------\n");
        
        for (i = 0;i <= b->max_order; i++) {
                cnt = 0;
                if (!list_empty(&b->order[i])) {
                        for (cur = b->order[i].next; cur != &b->order[i]; cur = cur->next)
                                cnt++;
                }
        
                printf("#%" PRIi "\t%5" PRIc "\t%7" PRIc "K\t%8" PRIi "K\t%6u\t",
                        i, cnt, SIZE2KB(cnt * (1 << i) * elem_size), SIZE2KB((1 << i) * elem_size), 1 << i);
                if (!list_empty(&b->order[i])) {
                        for (cur = b->order[i].next; cur != &b->order[i]; cur = cur->next) {
                                b->op->print_id(b, cur);
                                printf(" ");
                        }
                }
                printf("\n");
                        
                block_count += cnt;
                elem_count += (1 << i) * cnt;
        }
        printf("-----\t------\t--------\t----------\t---------------\n");
        printf("Buddy system contains %" PRIc " free elements (%" PRIc " blocks)\n" , elem_count, block_count);
}

/** @}
 */