memory: basic arena allocator primitive

This commit is contained in:
Andrei Alexeyev 2023-02-09 15:08:01 +01:00
parent bf7964926c
commit 8547f443b7
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GPG key ID: 72D26128040B9690
4 changed files with 186 additions and 1 deletions

127
src/memory/arena.c Normal file
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@ -0,0 +1,127 @@
/*
* This software is licensed under the terms of the MIT License.
* See COPYING for further information.
* ---
* Copyright (c) 2011-2019, Lukas Weber <laochailan@web.de>.
* Copyright (c) 2012-2019, Andrei Alexeyev <akari@taisei-project.org>.
*/
#include "taisei.h"
#include "arena.h"
#include "util.h"
#include "../util.h"
#define ARENA_MIN_ALLOC 4096
// NOTE: if we cared about 64-bit Linux only, mmap would be nice here…
// Unfortunately, some of the platforms we support *cough*emscripten*cough*
// don't even have virtual memory, so we can't have nice infinitely growable
// contiguous arenas.
static void *_arena_alloc_page(size_t s) {
return mem_alloc(s);
}
static void _arena_dealloc_page(MemArenaPage *p) {
mem_free(p);
}
static MemArenaPage *_arena_new_page(MemArena *arena, size_t min_size) {
auto alloc_size = topow2_u64(min_size + sizeof(MemArenaPage));
alloc_size = imax(min_size, ARENA_MIN_ALLOC);
auto page_size = alloc_size - sizeof(MemArenaPage);
MemArenaPage *p = _arena_alloc_page(alloc_size);
p->size = page_size;
p->arena = arena;
alist_append(&arena->pages, p);
arena->page_offset = 0;
arena->total_allocated += page_size;
return p;
}
static void _arena_delete_page(MemArena *arena, MemArenaPage *page) {
assume(page->arena == arena);
_arena_dealloc_page(page);
}
static void *_arena_alloc(MemArena *arena, size_t size, size_t align) {
auto page = NOT_NULL(arena->pages.last);
assume(page->arena == arena);
assume(page->next == NULL);
auto page_ofs = arena->page_offset;
size_t required, alignofs;
for(;;) {
auto available = page->size - page_ofs;
alignofs = align - ((uintptr_t)(page->data + page_ofs) & (align - 1));
required = alignofs + size;
if(available < required) {
page = _arena_new_page(arena, required);
assert(arena->page_offset == 0);
page_ofs = 0;
continue;
}
break;
}
void *p = page->data + page_ofs + alignofs;
arena->total_used += required;
arena->page_offset += required;
assert(arena->page_offset <= page->size);
assert(((uintptr_t)p & (align - 1)) == 0);
return p;
}
void marena_init(MemArena *arena, size_t min_size) {
*arena = (MemArena) { };
_arena_new_page(arena, min_size);
}
void marena_deinit(MemArena *arena) {
MemArenaPage *p;
while((p = alist_pop(&arena->pages))) {
_arena_delete_page(arena, p);
}
}
void marena_reset(MemArena *arena) {
auto used = arena->total_used;
arena->total_used = 0;
arena->page_offset = 0;
if(arena->pages.first->next) {
MemArenaPage *p;
while((p = alist_pop(&arena->pages))) {
_arena_delete_page(arena, p);
}
arena->total_allocated = 0;
p = _arena_new_page(arena, used);
assert(p == arena->pages.last);
}
assert(arena->pages.first != NULL);
assert(arena->pages.first == arena->pages.last);
}
void *marena_alloc(MemArena *arena, size_t size) {
return _arena_alloc(arena, size, alignof(max_align_t));
}
void *marena_alloc_array(MemArena *arena, size_t num_members, size_t size) {
return _arena_alloc(arena, mem_util_calc_array_size(num_members, size), alignof(max_align_t));
}
void *marena_alloc_aligned(MemArena *arena, size_t size, size_t align) {
assume(align > 0);
assume(!(align & (align - 1)));
if(align < alignof(max_align_t)) {
align = alignof(max_align_t);
}
return _arena_alloc(arena, size, align);
}

57
src/memory/arena.h Normal file
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@ -0,0 +1,57 @@
/*
* This software is licensed under the terms of the MIT License.
* See COPYING for further information.
* ---
* Copyright (c) 2011-2019, Lukas Weber <laochailan@web.de>.
* Copyright (c) 2012-2019, Andrei Alexeyev <akari@taisei-project.org>.
*/
#pragma once
#include "taisei.h"
#include "list.h"
typedef struct MemArena MemArena;
typedef struct MemArenaPage MemArenaPage;
struct MemArena {
LIST_ANCHOR(MemArenaPage) pages;
size_t page_offset;
size_t total_used;
size_t total_allocated;
};
struct MemArenaPage {
LIST_INTERFACE(MemArenaPage);
MemArena *arena;
size_t size;
alignas(alignof(max_align_t)) char data[];
};
void marena_init(MemArena *arena, size_t min_size)
attr_nonnull_all;
void marena_deinit(MemArena *arena)
attr_nonnull_all;
void marena_reset(MemArena *arena)
attr_nonnull_all;
void *marena_alloc(MemArena *arena, size_t size)
attr_alloc_size(2)
attr_malloc
attr_returns_allocated
attr_nonnull_all;
void *marena_alloc_array(MemArena *arena, size_t num_members, size_t size)
attr_alloc_size(2, 3)
attr_malloc
attr_returns_allocated
attr_nonnull_all;
void *marena_alloc_aligned(MemArena *arena, size_t size, size_t alignment)
attr_alloc_size(2)
attr_alloc_align(3)
attr_malloc
attr_returns_allocated
attr_nonnull_all;

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@ -48,7 +48,7 @@ void *mem_alloc(size_t size) {
void *mem_alloc_array(size_t num_members, size_t size) {
#if MEMALIGN_METHOD == MEMALIGN_METHOD_WIN32
size_t array_size = mem_calc_array_size(num_members, size);
size_t array_size = mem_util_calc_array_size(num_members, size);
void *p = NOT_NULL(_aligned_malloc(array_size, alignof(max_align_t)));
memset(p, 0, array_size);
return p;

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@ -1,4 +1,5 @@
memory_src = files(
'arena.c',
'memory.c',
)