memory.c
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/**
* \file This holds all stufff related our memory managent.
* I try the best as far as I can to reduce memory fragmentation
* and unneccessary calls to alloc and free.
*
* To achive this I try an approach described here as "Quick Fit".
* http://www.flounder.com/memory_allocation.htm
*
* The basic idea is to keep allocated memory segments and don't free
* them again. Instead I will put them in a tree indexed by their size.
* To get new memory I first have a look in the tree if there is
* a fitting memory segment. Fitting mean, larger or exactly the size
* I need. If there is one, use it. If not create a new one using
* usual malloc approach.
* I won't split the reagions at all because most likely they will be
* free soon again. This way I might waste some memory, so I have to
* keep an eye on this.
*
* Right now I don't build an upper limit for allocation. The limit
* still is the system memory itself.
*
* This is not implemented as a class because it will be used in the
* process of object creation.
*
* The data structure is a balanced tree with size as key.
* Under the size key is a list of elements of the same size.
*
* \author Georg Hopp
*
* \copyright
* Copyright © 2012 Georg Hopp
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <search.h>
#include <unistd.h>
#include "tr/memory.h"
#include "tr/tree_macros.h"
struct memSegment
{
size_t ref_count;
size_t size;
void * ptr;
TR_rbColor color;
struct memSegment * data;
struct memSegment * next;
struct memSegment * last;
struct memSegment * parent;
struct memSegment * left;
struct memSegment * right;
};
static
struct memSegment *
newElement(size_t size)
{
struct memSegment * element = malloc(size);
element->ref_count = 1;
element->size = size;
element->ptr = (void*)element + sizeof(struct memSegment);
element->data = element;
element->next = NULL;
element->last = NULL;
element->color = rbRed;
element->parent = NULL;
element->left = NULL;
element->right = NULL;
return element;
}
#ifdef MEM_OPT
static
int
_memSegmentFindCompare(const void * a, const void * b)
{
struct memSegment * _a = (struct memSegment *)a;
size_t _b = *(size_t *)b;
/*
* find the smallest bigger or equal size segment
*/
return _a->size < _b ? -1
: _a->size > _b && _a->left && _a->left->size >= _b ? 1 : 0;
}
static
int
_memSegmentCompare(const void * a, const void * b)
{
size_t _a = ((struct memSegment *)a)->size;
size_t _b = ((struct memSegment *)b)->size;
return _a < _b ? -1 : _a > _b ? 1 : 0;
}
/**
* insert element in tree
*/
static
struct memSegment *
insertElement(struct memSegment ** tree, struct memSegment * element)
{
struct memSegment * node = *tree;
struct memSegment * new_node = NULL;
int found;
element->next = NULL;
element->last = NULL;
element->color = rbRed;
element->parent = NULL;
element->left = NULL;
element->right = NULL;
TR_TREE_FIND(node, element, found, _memSegmentCompare);
// if tree is empty it's simple... :)
if (NULL == node) {
*tree = node = new_node = element;
} else {
// normal binary tree add....
if (found == 0) {
if (NULL == node->next) {
node->next = element;
node->last = element;
} else {
node->last->next = element;
node->last = element;
}
return node;
} else {
if (0 < found) {
node->left = element;
node->left->parent = node;
new_node = node = node->left;
} else {
node->right = element;
node->right->parent = node;
new_node = node = node->right;
}
}
}
/*
* handle reballancing rb style
*/
TR_TREE_BALANCE_INSERT(tree, node);
return new_node;
}
static
struct memSegment *
deleteElement(struct memSegment ** tree, size_t size)
{
struct memSegment * node = *tree;
struct memSegment * del_node;
struct memSegment * child;
struct memSegment * s;
int found;
// find the relevant node and it's parent
TR_TREE_FIND(node, &size, found, _memSegmentFindCompare);
//while (node) {
if (found != 0) {
return NULL;
} else {
if (NULL != node->next) {
if (NULL != node->parent) {
if (node == node->parent->left) {
node->parent->left = node->next;
} else {
node->parent->right = node->next;
}
} else {
*tree = node->next;
}
if (NULL != node->left) {
node->left->parent = node->next;
}
if (NULL != node->right) {
node->right->parent = node->next;
}
node->next->last = node->last;
node->next->color = node->color;
node->next->parent = node->parent;
node->next->left = node->left;
node->next->right = node->right;
return node;
}
}
del_node = node;
// now our cases follows...the first one is the same as with
// simple binary search trees. Two non null children.
// case 1: two children
if (NULL != node->left && NULL != node->right) {
struct memSegment * successor;
struct memSegment * tmpparent;
struct memSegment * tmpleft;
struct memSegment * tmpright;
TR_rbColor tmpcolor;
TR_TREE_INORDER_SUCC(node, successor);
tmpparent = successor->parent;
tmpleft = successor->left;
tmpright = successor->right;
tmpcolor = successor->color;
TR_TREE_REPLACE_NODE(tree, node, successor);
successor->color = node->color;
successor->left = node->left;
successor->left->parent = successor;
// the right one might be successor...
if (node->right == successor) {
successor->right = node;
node->parent = successor;
} else {
successor->right = node->right;
node->right->parent = successor;
node->parent = tmpparent;
tmpparent->left = node;
}
node->color = tmpcolor;
node->left = tmpleft;
node->right = tmpright;
}
// Precondition: n has at most one non-null child.
child = (NULL == node->right) ? node->left : node->right;
TR_TREE_REPLACE_NODE(tree, node, child);
// delete one child case
// TODO this is overly complex as simply derived from the function...
// maybe this can be simplified. Maybe not...check.
if (node->color == rbBlack) {
if (NULL != child && child->color == rbRed) {
child->color = rbBlack;
// done despite modifying tree itself if neccessary..
return del_node;
} else {
if (NULL != child) {
node = child;
} else {
node->color = rbBlack;
node->left = NULL;
node->right = NULL;
}
}
} else {
return del_node;
}
TR_TREE_BALANCE_DELETE(tree, node, s);
return del_node;
}
static
void
post(struct memSegment * tree, void (*cb)(struct memSegment *, int))
{
struct memSegment * previous = tree;
struct memSegment * node = tree;
int depth = 1;
/*
* I think this has something like O(n+log(n)) on a ballanced
* tree because I have to traverse back the rightmost leaf to
* the root to get a break condition.
*/
while (node) {
/*
* If we come from the right so nothing and go to our
* next parent.
*/
if (((NULL == node->left || previous == node->left)
&& NULL == node->right)
|| previous == node->right) {
struct memSegment * parent = node->parent;
cb(node, depth);
previous = node;
node = parent;
depth--;
continue;
}
if ((NULL == node->left || previous == node->left)) {
/*
* If there are no more elements to the left or we
* came from the left, process data.
*/
previous = node;
if (NULL != node->right) {
node = node->right;
depth++;
} else {
node = node->parent;
depth--;
}
} else {
/*
* if there are more elements to the left go there.
*/
previous = node;
node = node->left;
depth++;
}
}
}
struct memSegment * segments = NULL;
static
void
segmentFree(struct memSegment * segment, int depth)
{
while (NULL != segment) {
struct memSegment * next = segment->next;
free(segment);
segment = next;
}
}
#endif
void *
TR_reference(void * mem)
{
struct memSegment * seg = (mem - sizeof(struct memSegment));
seg->ref_count++;
return mem;
}
/*
* This tries to reflect the memory management behaviour of the
* GNU version of malloc. For other versions this might need
* to be changed to be optimal.
*
* However, GNU malloc keeps separate pools for each power of
* 2 memory size up to page size. So one page consists all of
* memory blocks of the same sizei (a power of 2).
*
* Also as far as I understand the smallest allocatable block is
* 8 bytes. At least the adresses are alwayse a multiple of 8.
*
* So lets say page size is 4096. There is nothing allocated
* right now. We allocate a block of 8 bytes. This will request
* a memory page from the OS. Then define it as a page containing
* 8 byte blocks and return the address of the first one of these.
* Any subsequent call to malloc for 8 bytes will return one of the
* blocks within this page as long as there are some left.
*
* So what we do here is up to page size round the request size up
* to the next power of 2 >= 8.
* Sizes greater then pagesize will be round up to the next
* multiple of pagesize. As far as I understand these are not
* pooled anyway.
*
* For now this assumes we are on a little endian machine.
*/
void *
TR_malloc(size_t size)
{
struct memSegment * seg = NULL;
long psize = sysconf(_SC_PAGESIZE);
size += sizeof(struct memSegment);
if (size > psize) {
if (0 != (size % psize)) {
// size if not a multiple of pagesize so bring it to one.
size = ((size / psize) + 1) * psize;
}
} else {
if (size < 8) {
size = 8;
} else {
size_t check = size >> 4;
size_t mask = 0x1F;
while (check >>= 1) {
mask = (mask << 1) | 1;
}
if (size != (size & ~(mask >> 1))) {
size = (size << 1) & ~mask;
}
}
}
#ifdef MEM_OPT
seg = deleteElement(&segments, size);
#endif
if (NULL == seg) {
seg = newElement(size);
}
return seg->ptr;
}
/**
* this is a really memory wasting solution....just to be able to
* use calloc, which might be faster then malloc/memset solution.
*
* Maybe this is a bad idea, as we need to memset the buffer anyway
* if it comes from our tree, which hopefully should be the majority
* of cases.
*/
void *
TR_calloc(size_t nmemb, size_t size)
{
size_t _size = nmemb * size;
void * mem = TR_malloc(_size);
memset(mem, 0, _size);
return mem;
}
void
TR_free(void ** mem)
{
if (NULL != *mem) {
struct memSegment * seg = (*mem - sizeof(struct memSegment));
if (1 < seg->ref_count) {
seg->ref_count--;
} else {
#ifdef MEM_OPT
insertElement(&segments, seg);
#else
free(seg);
#endif
}
*mem = NULL;
}
}
size_t
TR_getSize(void * mem)
{
struct memSegment * segment;
if (NULL == mem) {
return 0;
}
segment = (struct memSegment *)(mem - sizeof(struct memSegment));
return segment->size;
}
void
TR_cleanup()
{
#ifdef MEM_OPT
post(segments, segmentFree);
#endif
}
char *
TR_strdup(const char * src)
{
char * dup;
if (NULL == src) {
return NULL;
}
dup = TR_malloc(strlen(src)+1);
strcpy(dup, src);
return dup;
}
// vim: set ts=4 sw=4: