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/*************************************************************************
* Copyright (C) 2014 Tavian Barnes <tavianator@tavianator.com> *
* *
* This file is part of The Dimension Library. *
* *
* The Dimension Library is free software; you can redistribute it and/ *
* or modify it under the terms of the GNU Lesser General Public License *
* as published by the Free Software Foundation; either version 3 of the *
* License, or (at your option) any later version. *
* *
* The Dimension Library 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 *
* Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public *
* License along with this program. If not, see *
* <http://www.gnu.org/licenses/>. *
*************************************************************************/
/**
* @file
* Memory pool implementation.
*/
#include "internal.h"
#include "internal/concurrency.h"
#include <stdatomic.h>
/// Number of pointers per block, we want a block to fit in a single page.
#define DMNSN_POOL_BLOCK_SIZE (4096/sizeof(void *) - 4)
/// Number of pointers per tidy block
#define DMNSN_TIDY_BLOCK_SIZE ((4096 - 4*sizeof(void *))/(sizeof(void *) + sizeof(dmnsn_callback_fn *)))
/// A single block in a thread-specific pool.
typedef struct dmnsn_pool_block {
/// Current index into allocs[].
size_t i;
/// All allocations in the current block.
void *allocs[DMNSN_POOL_BLOCK_SIZE];
/// Tail pointer to the previous block in the global chain.
struct dmnsn_pool_block *prev;
} dmnsn_pool_block;
/// A single tidy block in a thread-specific pool.
typedef struct dmnsn_tidy_block {
/// Current index into allocs[].
size_t i;
/// All allocations in the current block.
void *allocs[DMNSN_TIDY_BLOCK_SIZE];
/// All cleanup callbacks in the current block.
dmnsn_callback_fn *cleanup_fns[DMNSN_TIDY_BLOCK_SIZE];
/// Tail pointer to the previous tidy block in the global chain.
struct dmnsn_tidy_block *prev;
} dmnsn_tidy_block;
/// dmnsn_pool implementation.
struct dmnsn_pool {
/// Thread-local regular block.
pthread_key_t thread_block;
/// Thread-local tidy block.
pthread_key_t thread_tidy_block;
/// Global chain of regular blocks.
atomic(dmnsn_pool_block *) chain;
/// Global chain of tidy blocks.
atomic(dmnsn_tidy_block *) tidy_chain;
};
dmnsn_pool *
dmnsn_new_pool(void)
{
dmnsn_pool *pool = DMNSN_MALLOC(dmnsn_pool);
dmnsn_key_create(&pool->thread_block, NULL);
dmnsn_key_create(&pool->thread_tidy_block, NULL);
atomic_store_explicit(&pool->chain, NULL, memory_order_relaxed);
atomic_store_explicit(&pool->tidy_chain, NULL, memory_order_relaxed);
return pool;
}
void *
dmnsn_palloc(dmnsn_pool *pool, size_t size)
{
dmnsn_pool_block *old_block = pthread_getspecific(pool->thread_block);
dmnsn_pool_block *new_block = old_block;
if (dmnsn_unlikely(!old_block || old_block->i == DMNSN_POOL_BLOCK_SIZE)) {
new_block = DMNSN_MALLOC(dmnsn_pool_block);
new_block->i = 0;
}
void *result = dmnsn_malloc(size);
new_block->allocs[new_block->i++] = result;
if (dmnsn_unlikely(new_block != old_block)) {
dmnsn_setspecific(pool->thread_block, new_block);
// Atomically update pool->chain
dmnsn_pool_block *old_chain = atomic_exchange(&pool->chain, new_block);
new_block->prev = old_chain;
}
return result;
}
void *
dmnsn_palloc_tidy(dmnsn_pool *pool, size_t size, dmnsn_callback_fn *cleanup_fn)
{
dmnsn_assert(cleanup_fn != NULL, "NULL cleanup_fn");
dmnsn_tidy_block *old_block = pthread_getspecific(pool->thread_tidy_block);
dmnsn_tidy_block *new_block = old_block;
if (dmnsn_unlikely(!old_block || old_block->i == DMNSN_TIDY_BLOCK_SIZE)) {
new_block = DMNSN_MALLOC(dmnsn_tidy_block);
new_block->i = 0;
}
void *result = dmnsn_malloc(size);
size_t i = new_block->i;
new_block->allocs[i] = result;
new_block->cleanup_fns[i] = cleanup_fn;
++new_block->i;
if (dmnsn_unlikely(new_block != old_block)) {
dmnsn_setspecific(pool->thread_tidy_block, new_block);
// Atomically update pool->tidy_chain
dmnsn_tidy_block *old_chain = atomic_exchange(&pool->tidy_chain, new_block);
new_block->prev = old_chain;
}
return result;
}
void
dmnsn_delete_pool(dmnsn_pool *pool)
{
if (!pool) {
return;
}
dmnsn_pool_block *block = atomic_load_explicit(&pool->chain, memory_order_relaxed);
while (block) {
// Free all the allocations
for (size_t i = block->i; i-- > 0;) {
dmnsn_free(block->allocs[i]);
}
// Free the block itself and go to the previous one
dmnsn_pool_block *saved = block;
block = block->prev;
dmnsn_free(saved);
}
dmnsn_tidy_block *tidy_block = atomic_load_explicit(&pool->tidy_chain, memory_order_relaxed);
while (tidy_block) {
// Free all the allocations
for (size_t i = tidy_block->i; i-- > 0;) {
void *ptr = tidy_block->allocs[i];
tidy_block->cleanup_fns[i](ptr);
dmnsn_free(ptr);
}
// Free the block itself and go to the previous one
dmnsn_tidy_block *saved = tidy_block;
tidy_block = tidy_block->prev;
dmnsn_free(saved);
}
dmnsn_key_delete(pool->thread_tidy_block);
dmnsn_free(pool);
}
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