/* Managed memory allocator. * * Author: Steffen Vogel * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University * SPDX-License-Identifier: Apache-2.0 */ #include #include #include #include #include #include #include #include #include #include #include #include using namespace villas; using namespace villas::node; using namespace villas::utils; using namespace villas::node::memory; static struct Allocation *managed_alloc(size_t len, size_t alignment, struct Type *m) { // Simple first-fit allocation struct Block *first = (struct Block *)m->_vd; struct Block *block; for (block = first; block != nullptr; block = block->next) { if (block->used) continue; char *cptr = (char *)block + sizeof(struct Block); size_t avail = block->length; uintptr_t uptr = (uintptr_t)cptr; /* Check alignment first; leave a gap at start of block to assure * alignment if necessary */ uintptr_t rem = uptr % alignment; uintptr_t gap = 0; if (rem != 0) { gap = alignment - rem; if (gap > avail) continue; // Next aligned address isn't in this block anymore cptr += gap; avail -= gap; } if (avail >= len) { if (gap > sizeof(struct Block)) { /* The alignment gap is big enough to fit another block. * The original block descriptor is already at the correct * position, so we just change its len and create a new block * descriptor for the actual block we're handling. */ block->length = gap - sizeof(struct Block); struct Block *newblock = (struct Block *)(cptr - sizeof(struct Block)); newblock->prev = block; newblock->next = block->next; block->next = newblock; newblock->used = false; newblock->length = len; block = newblock; } else { /* The gap is too small to fit another block descriptor, so we * must account for the gap length in the block length. */ block->length = len + gap; } if (avail > len + sizeof(struct Block)) { // Imperfect fit, so create another block for the remaining part struct Block *newblock = (struct Block *)(cptr + len); newblock->prev = block; newblock->next = block->next; block->next = newblock; if (newblock->next) newblock->next->prev = newblock; newblock->used = false; newblock->length = avail - len - sizeof(struct Block); } else { /* If this block was larger than the requested length, but only * by less than sizeof(struct Block), we may have wasted * memory by previous assignments to block->length. */ block->length = avail; } block->used = true; auto *ma = new struct Allocation; if (!ma) throw MemoryAllocationError(); ma->address = cptr; ma->type = m; ma->alignment = alignment; ma->length = len; ma->managed.block = block; return ma; } } // No suitable block found return nullptr; } static int managed_free(struct Allocation *ma, struct Type *m) { struct Block *block = ma->managed.block; // Try to merge it with neighbouring free blocks if (block->prev && !block->prev->used && block->next && !block->next->used) { // Special case first: both previous and next block are unused block->prev->length += block->length + block->next->length + 2 * sizeof(struct Block); block->prev->next = block->next->next; if (block->next->next) block->next->next->prev = block->prev; } else if (block->prev && !block->prev->used) { block->prev->length += block->length + sizeof(struct Block); block->prev->next = block->next; if (block->next) block->next->prev = block->prev; } else if (block->next && !block->next->used) { block->length += block->next->length + sizeof(struct Block); block->next = block->next->next; if (block->next) block->next->prev = block; } else { // no neighbouring free block, so just mark it as free block->used = false; } return 0; } struct Type *villas::node::memory::managed(void *ptr, size_t len) { struct Type *mt = (struct Type *)ptr; struct Block *mb; char *cptr = (char *)ptr; if (len < sizeof(struct Type) + sizeof(struct Block)) { auto logger = logging.get("memory:managed"); logger->info("Passed region is too small"); return nullptr; } // Initialize type mt->name = "managed"; mt->flags = 0; mt->alloc = managed_alloc; mt->free = managed_free; mt->alignment = 1; cptr += ALIGN(sizeof(struct Type), sizeof(void *)); // Initialize first free memory block mb = (struct Block *)cptr; mb->prev = nullptr; mb->next = nullptr; mb->used = false; cptr += ALIGN(sizeof(struct Block), sizeof(void *)); mb->length = len - (cptr - (char *)ptr); mt->_vd = (void *)mb; return mt; }