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More work on buddy allocator

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This commit is contained in:
Dale Weiler 2012-11-12 15:32:25 +00:00
parent 01b619d53d
commit baaa6407d5
1 changed files with 220 additions and 16 deletions
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222
mem.c
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@ -1,4 +1,5 @@
#include "gmqcc.h"
#include <assert.h>
/*
* GMQCC does a lot of allocations on shortly lived objects all of which
* call down to malloc/free internally. The overhead involved with these
@ -12,6 +13,19 @@
#define GMQCC_MEM_CORE 0x00000000000000AA
#define GMQCC_MEM_BSL -1
#define GMQCC_MEM_BSR 1
#define GMQCC_MEM_DEBUG 1
#ifdef GMQCC_MEM_DEBUG
# include <stdio.h>
# define GMQCC_MEM_TRACE(TAG, ...) \
do { \
printf("[mem:%s]: %s ", TAG, __func__); \
printf(__VA_ARGS__); \
printf("\n"); \
} while (0)
#else
# define GMQCC_MEM_TRACE(TAG, ...)
#endif
typedef unsigned long int mem_addr;
@ -21,11 +35,11 @@ static size_t mem_size = 0; /* heap size */
/* read or write to heap */
#define GMQCC_MEM_WRITEHEAP(OFFSET, TYPE, VALUE) *((TYPE *) ((unsigned char*)mem_heap + (OFFSET))) = (VALUE)
#define GMQCC_MEM_READHEAP (OFFSET, TYPE) ((TYPE)*((TYPE *)(((unsigned char*)mem_heap + (OFFSET)))))
#define GMQCC_MEM_READHEAP(OFFSET, TYPE) ((TYPE)*((TYPE *)(((unsigned char*)mem_heap + (OFFSET)))))
/* read of write first block to heap */
#define GMQCC_MEM_WRITEFBA(SIZE, ADDR) GMQCC_MEM_WRITEHEAP(mem_look + (SIZE) * sizeof(mem_addr), mem_addr, ADDR)
#define GMQCC_MEM_READFBA(SIZE) GMQCC_MEM_READHEAP (mem_look + (SIZE) * sizeof(mem_addr), ADDR)
#define GMQCC_MEM_READFBA(SIZE) GMQCC_MEM_READHEAP (mem_look + (SIZE) * sizeof(mem_addr), mem_addr)
/* read and write block sizes from heap */
#define GMQCC_MEM_WRITEBS(ADDR, SIZE) GMQCC_MEM_WRITEHEAP(ADDR, mem_addr, (SIZE))
@ -44,7 +58,11 @@ static size_t mem_size = 0; /* heap size */
#define GMQCC_MEM_MARKUSED(ADDR) GMQCC_MEM_WRITEHEAP((ADDR) + 1 * sizeof(mem_addr), mem_addr, GMQCC_MEM_USED)
#define GMQCC_MEM_MARKFREE(ADDR) GMQCC_MEM_WRITEHEAP((ADDR) + 1 * sizeof(mem_addr), mem_addr, GMQCC_MEM_FREE)
/* Has block? */
#define GMQCC_MEM_HASBLOCK(SIZE) (GMQCC_MEM_READFBA(size) != 0)
static void mem_init_table(size_t size) {
GMQCC_MEM_TRACE("flow", "(%lu)", size);
size_t i;
mem_look = 8 * ((mem_addr)1 << (size - 1)) + sizeof(mem_addr);
@ -58,7 +76,7 @@ static void mem_init_table(size_t size) {
GMQCC_MEM_WRITEHEAP(mem_look + sizeof(mem_addr) * size, mem_addr, sizeof(mem_addr));
GMQCC_MEM_WRITEHEAP(sizeof(mem_addr), mem_addr, size);
GMQCC_MEM_MARKFREE (sizeof(mem_addr) << 1);
GMQCC_MEM_MARKFREE (sizeof(mem_addr) * 2);
GMQCC_MEM_WRITEHEAP(sizeof(mem_addr) * 3, mem_addr, 0);
GMQCC_MEM_WRITEHEAP(sizeof(mem_addr) * 4, mem_addr, 0);
}
@ -69,33 +87,171 @@ static size_t mem_getnbs(const size_t need) {
size_t s = 1;
while (need > b) {
b >>= 1;
b *= 2;
s ++;
}
return s;
}
static void mem_removeblock(mem_addr a, size_t size) {
mem_addr p = GMQCC_MEM_GETADDROFPS(a);
mem_addr n = GMQCC_MEM_GETADDROFFS(a);
GMQCC_MEM_SETADDROFPS(a, ~((mem_addr)0));
GMQCC_MEM_SETADDROFFS(a, ~((mem_addr)0));
/* handle singles in list */
if ((p == 0) && (n == 0)) {
GMQCC_MEM_WRITEFBA(size, 0);
return;
}
/* first in list has different sibling semantics */
if (p == 0) {
GMQCC_MEM_WRITEFBA (size, n);
GMQCC_MEM_SETADDROFPS(n, 0);
return;
}
/* last item also has special meaning :) */
if (n == 0) {
GMQCC_MEM_SETADDROFFS(p, 0);
return;
}
/* middle of list */
GMQCC_MEM_SETADDROFPS(n, p);
GMQCC_MEM_SETADDROFFS(p, n);
}
static int mem_createblock(const size_t size) {
mem_addr parent;
int test;
GMQCC_MEM_TRACE("flow", "(%lu)", size);
if (GMQCC_MEM_HASBLOCK(size))
return 0;
if (size > GMQCC_MEM_READHEAP(mem_look, mem_addr))
abort();
/* recrusive ... */
if ((test = mem_createblock(size + 1)) != 0)
return test;
/* safe splits assured */
parent = GMQCC_MEM_READFBA(size + 1);
mem_removeblock(parent, size + 1);
/* split it */
GMQCC_MEM_WRITEFBA(size, parent);
{
/* find center and split */
mem_addr block = parent + 8 * ((mem_addr)1 << (size - 1));
mem_addr left = parent;
mem_addr right = block;
GMQCC_MEM_TRACE(
"dump",
"block info:\n left addr: %lu\n right addr: %lu\n prev addr: %lu",
left, right, parent
);
/* left half */
GMQCC_MEM_WRITEHEAP (left, mem_addr, size);
GMQCC_MEM_MARKFREE (left);
GMQCC_MEM_SETADDROFPS(left, 0);
GMQCC_MEM_SETADDROFFS(left, right);
/* right half */
GMQCC_MEM_WRITEHEAP (right, mem_addr, size);
GMQCC_MEM_MARKFREE (right);
GMQCC_MEM_SETADDROFPS(right, left);
GMQCC_MEM_SETADDROFPS(right, 0);
}
return 0;
}
static mem_addr mem_allocblock(const size_t size) {
GMQCC_MEM_TRACE("flow", "(%lu)", size);
int test = mem_createblock(size);
mem_addr first;
mem_addr next;
if (test != 0)
return 0;
/* first free one */
first = GMQCC_MEM_READFBA (size);
next = GMQCC_MEM_GETADDROFFS(first);
mem_removeblock(first, size);
GMQCC_MEM_WRITEFBA(next, size);
GMQCC_MEM_MARKUSED(first);
return first;
}
static int mem_getside(mem_addr addr, const size_t size) {
size_t real = addr - sizeof(mem_addr);
size_t next = ((mem_addr)1 << (size));
assert((real % 8) == 0); /* blow up */
real /= 8;
return ((real % next) == 0)? GMQCC_MEM_BSL : GMQCC_MEM_BSR;
}
static mem_addr mem_getaddr(mem_addr start, const size_t size) {
size_t length = (((mem_addr)1 << (size - 1)) * 8);
switch (mem_getside(start, size)) {
case GMQCC_MEM_BSL: return start + length;
case GMQCC_MEM_BSR: return start - length;
}
/* if reached blow up */
return (abort(), 1);
}
static void mem_addblock(mem_addr a, size_t s) {
mem_addr first = GMQCC_MEM_READFBA(s);
if (first == 0) {
/* only block */
GMQCC_MEM_WRITEFBA (s, a);
GMQCC_MEM_SETADDROFPS(a, 0);
GMQCC_MEM_SETADDROFFS(a, 0);
} else {
/* add to front */
GMQCC_MEM_WRITEFBA (s, a);
GMQCC_MEM_SETADDROFPS(a, 0);
GMQCC_MEM_SETADDROFFS(a, first);
GMQCC_MEM_SETADDROFPS(first, a);
}
}
void mem_init(size_t size) {
size_t alloc = 0;
size_t alloc = size;
size_t count = 1;
size_t block = 1;
/* blow up if too small */
assert (sizeof(void*) == sizeof(mem_addr));
if (!(mem_heap = malloc(size)))
abort();
memset(mem_heap, GMQCC_MEM_CORE, size);
mem_size = size;
alloc = size - (2 * sizeof(mem_addr));
alloc -= 2 * sizeof(mem_addr);
while (alloc + sizeof(mem_addr) > 8 * block) {
alloc -= sizeof(mem_addr);
block <<= 1;
block *= 2;
count ++;
}
/* over shot ? */
block >>= 1;
block /= 2;
count --;
mem_init_table(count);
@ -108,10 +264,58 @@ void mem_destroy() {
}
void *mem_alloc(size_t amount) {
GMQCC_MEM_TRACE("flow", "(%lu)", amount);
size_t need = amount + 4 * sizeof(mem_addr);
size_t size = mem_getnbs (need);
mem_addr block = mem_allocblock(size);
if (!block) return NULL;
GMQCC_MEM_TRACE("dump", "will allocate %lu size block", size);
/* standard behaviour */
if (block == 0)
return NULL;
GMQCC_MEM_TRACE("dump", "returning offset %lu", block);
return mem_heap + block + 4 * sizeof(mem_addr);
}
void mem_free(void *ptr) {
mem_addr start = (mem_addr)(ptr - mem_heap) - 4 * sizeof(mem_addr);
size_t size = GMQCC_MEM_READHEAP(start, mem_addr);
mem_addr addr = mem_getaddr(start, size);
int side = mem_getside(start, size);
GMQCC_MEM_TRACE (
"dump",
"deallocating %s buddy (neighbour at %lu)",
(side == GMQCC_MEM_BSL) ? "left" : "right",
addr
);
GMQCC_MEM_MARKFREE(start);
/* while free block merge */
while ((GMQCC_MEM_READHEAP(addr + 1 * sizeof(mem_addr), mem_addr)) == (mem_addr)GMQCC_MEM_FREE) {
GMQCC_MEM_TRACE("dump", "merging ...");
mem_removeblock(addr, size);
/* find new start */
start = addr < start ? addr : start;
size ++;
if (size == GMQCC_MEM_READHEAP(mem_look, mem_addr))
break; /* blow up */
addr = mem_getaddr(start, size);
GMQCC_MEM_TRACE("dump", "new block start is %lu, buddy at %lu", start, addr);
}
/* add it */
GMQCC_MEM_WRITEBS(start, size);
mem_addblock (start, size);
}
#include <stdio.h>
int main() {
mem_init(1330);
char *p = mem_alloc(sizeof(char) * 5);
/* blows up on second alloc, why? char *x = mem_alloc(200); */
}