path: root/lib/librte_eal/common/malloc_elem.c

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2014 Intel Corporation
 */
#include <stdint.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <sys/queue.h>

#include <rte_memory.h>
#include <rte_eal.h>
#include <rte_launch.h>
#include <rte_per_lcore.h>
#include <rte_lcore.h>
#include <rte_debug.h>
#include <rte_common.h>
#include <rte_spinlock.h>

#include "malloc_elem.h"
#include "malloc_heap.h"

#define MIN_DATA_SIZE (RTE_CACHE_LINE_SIZE)

/*
 * Initialize a general malloc_elem header structure
 */
void
malloc_elem_init(struct malloc_elem *elem,
		struct malloc_heap *heap, const struct rte_memseg *ms, size_t size)
{
	elem->heap = heap;
	elem->ms = ms;
	elem->prev = NULL;
	memset(&elem->free_list, 0, sizeof(elem->free_list));
	elem->state = ELEM_FREE;
	elem->size = size;
	elem->pad = 0;
	set_header(elem);
	set_trailer(elem);
}

/*
 * Initialize a dummy malloc_elem header for the end-of-memseg marker
 */
void
malloc_elem_mkend(struct malloc_elem *elem, struct malloc_elem *prev)
{
	malloc_elem_init(elem, prev->heap, prev->ms, 0);
	elem->prev = prev;
	elem->state = ELEM_BUSY; /* mark busy so its never merged */
}

/*
 * calculate the starting point of where data of the requested size
 * and alignment would fit in the current element. If the data doesn't
 * fit, return NULL.
 */
static void *
elem_start_pt(struct malloc_elem *elem, size_t size, unsigned align,
		size_t bound)
{
	const size_t bmask = ~(bound - 1);
	uintptr_t end_pt = (uintptr_t)elem +
			elem->size - MALLOC_ELEM_TRAILER_LEN;
	uintptr_t new_data_start = RTE_ALIGN_FLOOR((end_pt - size), align);
	uintptr_t new_elem_start;

	/* check boundary */
	if ((new_data_start & bmask) != ((end_pt - 1) & bmask)) {
		end_pt = RTE_ALIGN_FLOOR(end_pt, bound);
		new_data_start = RTE_ALIGN_FLOOR((end_pt - size), align);
		end_pt = new_data_start + size;
		if (((end_pt - 1) & bmask) != (new_data_start & bmask))
			return NULL;
	}

	new_elem_start = new_data_start - MALLOC_ELEM_HEADER_LEN;

	/* if the new start point is before the exist start, it won't fit */
	return (new_elem_start < (uintptr_t)elem) ? NULL : (void *)new_elem_start;
}

/*
 * use elem_start_pt to determine if we get meet the size and
 * alignment request from the current element
 */
int
malloc_elem_can_hold(struct malloc_elem *elem, size_t size,	unsigned align,
		size_t bound)
{
	return elem_start_pt(elem, size, align, bound) != NULL;
}

/*
 * split an existing element into two smaller elements at the given
 * split_pt parameter.
 */
static void
split_elem(struct malloc_elem *elem, struct malloc_elem *split_pt)
{
	struct malloc_elem *next_elem = RTE_PTR_ADD(elem, elem->size);
	const size_t old_elem_size = (uintptr_t)split_pt - (uintptr_t)elem;
	const size_t new_elem_size = elem->size - old_elem_size;

	malloc_elem_init(split_pt, elem->heap, elem->ms, new_elem_size);
	split_pt->prev = elem;
	next_elem->prev = split_pt;
	elem->size = old_elem_size;
	set_trailer(elem);
}

/*
 * Given an element size, compute its freelist index.
 * We free an element into the freelist containing similarly-sized elements.
 * We try to allocate elements starting with the freelist containing
 * similarly-sized elements, and if necessary, we search freelists
 * containing larger elements.
 *
 * Example element size ranges for a heap with five free lists:
 *   heap->free_head[0] - (0   , 2^8]
 *   heap->free_head[1] - (2^8 , 2^10]
 *   heap->free_head[2] - (2^10 ,2^12]
 *   heap->free_head[3] - (2^12, 2^14]
 *   heap->free_head[4] - (2^14, MAX_SIZE]
 */
size_t
malloc_elem_free_list_index(size_t size)
{
#define MALLOC_MINSIZE_LOG2   8
#define MALLOC_LOG2_INCREMENT 2

	size_t log2;
	size_t index;

	if (size <= (1UL << MALLOC_MINSIZE_LOG2))
		return 0;

	/* Find next power of 2 >= size. */
	log2 = sizeof(size) * 8 - __builtin_clzl(size-1);

	/* Compute freelist index, based on log2(size). */
	index = (log2 - MALLOC_MINSIZE_LOG2 + MALLOC_LOG2_INCREMENT - 1) /
	        MALLOC_LOG2_INCREMENT;

	return index <= RTE_HEAP_NUM_FREELISTS-1?
	        index: RTE_HEAP_NUM_FREELISTS-1;
}

/*
 * Add the specified element to its heap's free list.
 */
void
malloc_elem_free_list_insert(struct malloc_elem *elem)
{
	size_t idx;

	idx = malloc_elem_free_list_index(elem->size - MALLOC_ELEM_HEADER_LEN);
	elem->state = ELEM_FREE;
	LIST_INSERT_HEAD(&elem->heap->free_head[idx], elem, free_list);
}

/*
 * Remove the specified element from its heap's free list.
 */
static void
elem_free_list_remove(struct malloc_elem *elem)
{
	LIST_REMOVE(elem, free_list);
}

/*
 * reserve a block of data in an existing malloc_elem. If the malloc_elem
 * is much larger than the data block requested, we split the element in two.
 * This function is only called from malloc_heap_alloc so parameter checking
 * is not done here, as it's done there previously.
 */
struct malloc_elem *
malloc_elem_alloc(struct malloc_elem *elem, size_t size, unsigned align,
		size_t bound)
{
	struct malloc_elem *new_elem = elem_start_pt(elem, size, align, bound);
	const size_t old_elem_size = (uintptr_t)new_elem - (uintptr_t)elem;
	const size_t trailer_size = elem->size - old_elem_size - size -
		MALLOC_ELEM_OVERHEAD;

	elem_free_list_remove(elem);

	if (trailer_size > MALLOC_ELEM_OVERHEAD + MIN_DATA_SIZE) {
		/* split it, too much free space after elem */
		struct malloc_elem *new_free_elem =
				RTE_PTR_ADD(new_elem, size + MALLOC_ELEM_OVERHEAD);

		split_elem(elem, new_free_elem);
		malloc_elem_free_list_insert(new_free_elem);
	}

	if (old_elem_size < MALLOC_ELEM_OVERHEAD + MIN_DATA_SIZE) {
		/* don't split it, pad the element instead */
		elem->state = ELEM_BUSY;
		elem->pad = old_elem_size;

		/* put a dummy header in padding, to point to real element header */
		if (elem->pad > 0) { /* pad will be at least 64-bytes, as everything
		                     * is cache-line aligned */
			new_elem->pad = elem->pad;
			new_elem->state = ELEM_PAD;
			new_elem->size = elem->size - elem->pad;
			set_header(new_elem);
		}

		return new_elem;
	}

	/* we are going to split the element in two. The original element
	 * remains free, and the new element is the one allocated.
	 * Re-insert original element, in case its new size makes it
	 * belong on a different list.
	 */
	split_elem(elem, new_elem);
	new_elem->state = ELEM_BUSY;
	malloc_elem_free_list_insert(elem);

	return new_elem;
}

/*
 * join two struct malloc_elem together. elem1 and elem2 must
 * be contiguous in memory.
 */
static inline void
join_elem(struct malloc_elem *elem1, struct malloc_elem *elem2)
{
	struct malloc_elem *next = RTE_PTR_ADD(elem2, elem2->size);
	elem1->size += elem2->size;
	next->prev = elem1;
}

/*
 * free a malloc_elem block by adding it to the free list. If the
 * blocks either immediately before or immediately after newly freed block
 * are also free, the blocks are merged together.
 */
int
malloc_elem_free(struct malloc_elem *elem)
{
	if (!malloc_elem_cookies_ok(elem) || elem->state != ELEM_BUSY)
		return -1;

	rte_spinlock_lock(&(elem->heap->lock));
	size_t sz = elem->size - sizeof(*elem) - MALLOC_ELEM_TRAILER_LEN;
	uint8_t *ptr = (uint8_t *)&elem[1];
	struct malloc_elem *next = RTE_PTR_ADD(elem, elem->size);
	if (next->state == ELEM_FREE){
		/* remove from free list, join to this one */
		elem_free_list_remove(next);
		join_elem(elem, next);
		sz += (sizeof(*elem) + MALLOC_ELEM_TRAILER_LEN);
	}

	/* check if previous element is free, if so join with it and return,
	 * need to re-insert in free list, as that element's size is changing
	 */
	if (elem->prev != NULL && elem->prev->state == ELEM_FREE) {
		elem_free_list_remove(elem->prev);
		join_elem(elem->prev, elem);
		sz += (sizeof(*elem) + MALLOC_ELEM_TRAILER_LEN);
		ptr -= (sizeof(*elem) + MALLOC_ELEM_TRAILER_LEN);
		elem = elem->prev;
	}
	malloc_elem_free_list_insert(elem);

	/* decrease heap's count of allocated elements */
	elem->heap->alloc_count--;

	memset(ptr, 0, sz);

	rte_spinlock_unlock(&(elem->heap->lock));

	return 0;
}

/*
 * attempt to resize a malloc_elem by expanding into any free space
 * immediately after it in memory.
 */
int
malloc_elem_resize(struct malloc_elem *elem, size_t size)
{
	const size_t new_size = size + elem->pad + MALLOC_ELEM_OVERHEAD;
	/* if we request a smaller size, then always return ok */
	if (elem->size >= new_size)
		return 0;

	struct malloc_elem *next = RTE_PTR_ADD(elem, elem->size);
	rte_spinlock_lock(&elem->heap->lock);
	if (next ->state != ELEM_FREE)
		goto err_return;
	if (elem->size + next->size < new_size)
		goto err_return;

	/* we now know the element fits, so remove from free list,
	 * join the two
	 */
	elem_free_list_remove(next);
	join_elem(elem, next);

	if (elem->size - new_size >= MIN_DATA_SIZE + MALLOC_ELEM_OVERHEAD) {
		/* now we have a big block together. Lets cut it down a bit, by splitting */
		struct malloc_elem *split_pt = RTE_PTR_ADD(elem, new_size);
		split_pt = RTE_PTR_ALIGN_CEIL(split_pt, RTE_CACHE_LINE_SIZE);
		split_elem(elem, split_pt);
		malloc_elem_free_list_insert(split_pt);
	}
	rte_spinlock_unlock(&elem->heap->lock);
	return 0;

err_return:
	rte_spinlock_unlock(&elem->heap->lock);
	return -1;
}