CSAPP: Malloc Lab 7
csapp malloc optimization lab ics
本次Lab真是CSAPP系列Lab中最恶心的Lab了！
这是《深入理解计算机系统》第二版配套Lab中的第7个Lab，对应本书的第9章：虚拟存储器。
下载地址：http://csapp.cs.cmu.edu/im/labs/malloclab.tar
Lab的要求是自己实现类似GNU Libc的malloc和free函数，也就是实现一个动态内存分配器，让你亲手管理一个程序的堆内存分配。最后会从吞吐量（单位时间可执行次数）和空间利用率两个方面进行评估。
本书中介绍了不少空闲链表的形式、分配策略，以及每个堆块的布局，诸如：
- 隐式空闲链表，只记录每个块的大小，分配时遍历整个堆寻找大小适合的块
- 显式空闲链表，在空闲块中额外记录前一个、后一个空闲块的位置，可以节省遍历时间
- 分离空闲链表，维护多个链表，将不同大小类的块分到同一个链表中
- 首次适配：选择第一个合适的块
- 下次适配：每次搜索从上次结束的地方开始
- 最佳适配：选择大小合适的最小块
其他实现与堆块的布局在此就不赘述了~书上都有所介绍
这个Lab我整整做了4天多，前三天一直在Debug，直到最后一天才能正常运行，然后又花了几个小时优化才达到满分……
我的思路是空闲链表+BST：
- 使用一小撮空闲链表来维护较小的空闲块
- 使用二叉搜索树来维护大的空闲块链表
- 所有的链表只存一种大小的空闲块
- 具体如图所示，二叉搜索树的每个节点都是一个链表的头部
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优化策略：
1、已分配的块可以省略脚部（Footer）。那么相邻空闲块合并时从何得知前一块是不是空闲呢？我们已经知道，块是按8字节对齐的，也就是说块头部中存储的块的大小是8的倍数，二进制表示中最后三位都是0。而在头部中，最低一位是存储当前块的分配状况的，那么就拿第二位来存储前一个块的分配情况好了。这样我们可以在合并时检查自己头部来得到前一块是不是被分配了，如果没有被分配，就与之合并。
2、块指针可以用4字节保存。虽然在64位机器中，指针是64位的，不过由于本次Lab的writeup中指出
Because we are running on 64-bit machines, your allocator must be coded accordingly, with one exception: the size of the heap will never be greater than or equal to 2^32 bytes. This does not imply anything about the location of the heap, but there is a neat optimization that can be done using this information. However, be very, very careful if you decide to take advantage of this fact.
因而我们可以只记录每个地址相对于堆起始地址的偏移量，这个偏移量是32位的，这个改进可以使得块大小最小达到16字节！
嗯……我也只想到了这么多，既然满分了就不再多想了……
下附完整代码~里面有些宏函数的定义，显示起来可能略乱……
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/* * mm.c * * Name: LegendaryPaladin * 姓名：轩辕奇侠 * * Brief introduction: * This solution used an algorithm with segregated free list * and a binary search tree combined to maximize both space utilization * and throughput. Please note that each free list is a unique size class, * which means it only contains blocks with EXACTLY THE SAME SIZE. * * Details of binary search tree: * The BST is used to store free blocks sized larger than a specific * threshold (I set it to 40 bytes), of which each node is a header of a * free list of a same size, When searching for a free block in BST, * I applied the best-fit policy which selects the free block with * approximately minimum size among all the blocks sized larger than * requested. * * Details of segregated free list: * I set up a small array to store the headers of segregated free lists. * Each free list, as described above, has blocks with a same size. Blocks * which is not large enough to be stored in BST will be stored here. * * Block layout: * Allocated block: * * [Header: <size><prev_alloc><1>] * [Payload...] * * Large free block: * * [Header: <size><prev_alloc><0>] * [4-byte pointer to next block with same size] * [4-byte pointer to previous block with same size] * [Pointer to its left child in BST] * [Pointer to its right child in BST] * [Pointer to the pointer to itself in its parent block in BST] * [...] * [Footer: <size><0>] * * Small free block: * * [Header: <size><prev_alloc><0>] * [4-byte pointer to next block with same size] * [4-byte pointer to previous block with same size] * [...] * [Footer: <size><0>] * * Note that I omitted the footer of allocated block, instead, I * stored its allocation info in the header of next block. * * * 概述: * 本次作业，我通过分离空闲链表 + 二叉搜索树来实现空间利用率和效率的 * 最大化。注意我的每个链表都只存储一种大小的空闲块。 * * 二叉搜索树: * 二叉搜索树用于存大于某个特定阈值的块（我设为40字节），每个节点是 * 具有该大小的空闲块链表的表头。在树中查找结点的时候，我会使用“最优适配” * 策略，选择树中大于请求大小的块中近似最小的那个。 * * 分离空闲链表: * 我给分离空闲链表的表头开了个小数组，每个空闲链表同样也只存一种大小的块。 * 大小不够放到树里的块会放到这里。 * * 块布局: * 已分配块: * * [头部: <大小><上一块分配状况><1>] * [有效载荷...] * * 大的空闲块: * * [头部: <大小><上一块分配状况><0>] * [指向下一个相同大小块的4字节指针] * [指向上一个相同大小块的4字节指针] * [指向左儿子的指针] * [指向右儿子的指针] * [指向它父亲指向它的指针的指针……] * [...] * [脚部: <大小><0>] * * 小的空闲块: * * [头部: <大小><上一块分配状况><0>] * [指向下一个相同大小块的4字节指针] * [指向上一个相同大小块的4字节指针] * [...] * [脚部: <大小><0>] * * 注意我把已分配块的脚部省略了，把它的分配状态信息 * 存到了下一个块的头部。 * */ #include <assert.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> /* Other helper headers */ #include <linux/kernel.h> #include <linux/stddef.h> #include "mm.h" #include "memlib.h" /* do not change the following! */ #ifdef DRIVER /* create aliases for driver tests */ #define malloc mm_malloc #define free mm_free #define realloc mm_realloc #define calloc mm_calloc #endif /* def DRIVER */ typedef void *block_ptr; /* Global var and data structure pointers */ static char *heap_listp = 0; /* Pointer to first block */ static block_ptr larger_bin_root; /* Root of the BST which contains larger blocks */ static block_ptr *bins; /* Array of the headers of segregated free lists */ static const unsigned int fixed_bin_count = 5; /* Number of segregated free lists */ #ifdef DEBUG static int operid; #endif /* Function prototypes */ static block_ptr coalesce(block_ptr bp); static block_ptr extend_heap(size_t words); static void place(block_ptr bp, size_t asize); static void insert_free_block(block_ptr bp, size_t blocksize); static void printblock(block_ptr bp); static void checkblock(block_ptr bp); static block_ptr find_fit(size_t asize); #ifdef DEBUG static void printtree(block_ptr node, int depth); #endif /* Macros and utility inline functions */ /* Single word (4) or double word (8) alignment */ #define ALIGNMENT 8 /* Round size up to ALIGNMENT */ #define ALIGN(size) (((size) + (ALIGNMENT - 1)) & ~0x7) /* Basic constants */ #define WSIZE 4 /* Word and header/footer size (bytes) */ #define DSIZE 8 /* Doubleword size (bytes) */ #define BLOCKSIZE (1 << 6) /* Extend heap by this amount (bytes) */ #define MAX(x, y) ((x) > (y)? (x) : (y)) /* Pack a size and allocated bit into a word */ #define PACK(size, alloc) ((size) | (alloc)) /* Read and write a word at address p */ #define GET(p) (*(unsigned int *)(p)) #define PUTTRUNC(p, val) (GET(p) = (val)) /* Write header info at address p without modifying prev_alloc */ #define PUT(p, val) (GET(p) = (GET(p) & 0x2) | (val)) /* Read the size and allocated fields from address p */ #define GET_SIZE(p) (GET(p) & ~0x7) #define GET_ALLOC(p) (GET(p) & 0x1) /* Given block ptr bp, compute address of its header and footer */ #define HDRP(bp) ((char *)(bp) - WSIZE) #define FTRP(bp) ((char *)(bp) + GET_SIZE(HDRP(bp)) - DSIZE) /* Given block ptr bp, compute address of next and previous blocks */ #define NEXT_BLKP(bp) ((char *)(bp) + GET_SIZE(((char *)(bp) - WSIZE))) #define PREV_BLKP(bp) ((char *)(bp) - GET_SIZE(((char *)(bp) - DSIZE))) /* Given block ptr bp, set next block's prev_alloc */ #define SET_ALLOC(bp) (GET(HDRP(NEXT_BLKP(bp))) |= 0x2) #define SET_UNALLOC(bp) (GET(HDRP(NEXT_BLKP(bp))) &= ~0x2) /* Given block ptr bp, get prev_alloc */ #define GET_PREV_ALLOC(bp) (GET(HDRP(bp)) & 0x2) /* Given a freed block ptr bp, compute 'address' of next and previous blocks of same size */ #define NEXT_SAMESZ_BLKP(bp) (*(unsigned int *)(bp)) #define PREV_SAMESZ_BLKP(bp) (*(unsigned int *)((char *)(bp) + WSIZE)) #define WNULL 0U /* Convert 4-byte address to 8-byte address */ static inline block_ptr word_to_ptr(unsigned int w) { return ((w) == WNULL ? NULL : (block_ptr)((unsigned int)(w) + 0x800000000UL)); } /* Convert 8-byte address to 4-byte address */ static inline unsigned int ptr_to_word(block_ptr p) { return ((p) == NULL ? WNULL : (unsigned int)((unsigned long)(p) - 0x800000000UL)); } /* The following are macros for BST node blocks */ /* Check if this block is large enough to be a BST node */ #define IS_OVER_BST_SIZE(size) ((size) > DSIZE * fixed_bin_count) #define IS_BST_NODE(bp) (IS_OVER_BST_SIZE(GET_SIZE(HDRP(bp)))) /* Given BST block ptr bp, compute address of its left child or right child */ #define LCHLD_BLKPREF(bp) ((block_ptr *)((char *)(bp) + DSIZE)) #define RCHLD_BLKPREF(bp) ((block_ptr *)((char *)(bp) + DSIZE * 2)) /* Crap-like triple pointer > < */ #define PARENT_CHLDSLOTPREF(bp) ((block_ptr **)((char *)(bp) + DSIZE * 3)) #define LCHLD_BLKP(bp) (*LCHLD_BLKPREF(bp)) #define RCHLD_BLKP(bp) (*RCHLD_BLKPREF(bp)) #define PARENT_CHLDSLOTP(bp) (*PARENT_CHLDSLOTPREF(bp)) /* Reset the fields of a free block bp */ #define reset_block(bp) \ { \ NEXT_SAMESZ_BLKP(bp) = WNULL; \ PREV_SAMESZ_BLKP(bp) = WNULL; \ if (IS_BST_NODE(bp)) \ { \ LCHLD_BLKP(bp) = NULL; \ RCHLD_BLKP(bp) = NULL; \ PARENT_CHLDSLOTP(bp) = NULL; \ } \ } /* Remove bp from its free list */ #define remove_linked_freed_block(bp) \ { \ if (PREV_SAMESZ_BLKP(bp)) \ NEXT_SAMESZ_BLKP(word_to_ptr(PREV_SAMESZ_BLKP(bp))) = NEXT_SAMESZ_BLKP(bp); \ if (NEXT_SAMESZ_BLKP(bp)) \ PREV_SAMESZ_BLKP(word_to_ptr(NEXT_SAMESZ_BLKP(bp))) = PREV_SAMESZ_BLKP(bp); \ } static inline void remove_freed_block(block_ptr bp) { if (IS_BST_NODE(bp) && PARENT_CHLDSLOTP(bp)) { /* I hate deleting node. */ block_ptr l = LCHLD_BLKP(bp), r = RCHLD_BLKP(bp), cur; if ((cur = word_to_ptr(NEXT_SAMESZ_BLKP(bp)))) { PARENT_CHLDSLOTP(cur) = PARENT_CHLDSLOTP(bp); *PARENT_CHLDSLOTP(bp) = cur; LCHLD_BLKP(cur) = l; if (l) PARENT_CHLDSLOTP(l) = LCHLD_BLKPREF(cur); RCHLD_BLKP(cur) = r; if (r) PARENT_CHLDSLOTP(r) = RCHLD_BLKPREF(cur); } else if (l && r) { /* Find left-most node in right branch to replace curr */ if (!(cur = LCHLD_BLKP(r))) { /* Right child doesn't have lchild */ LCHLD_BLKP(r) = l; PARENT_CHLDSLOTP(r) = PARENT_CHLDSLOTP(bp); *PARENT_CHLDSLOTP(bp) = r; PARENT_CHLDSLOTP(l) = LCHLD_BLKPREF(r); } else { while (LCHLD_BLKP(cur)) cur = LCHLD_BLKP(cur); *PARENT_CHLDSLOTP(bp) = cur; *PARENT_CHLDSLOTP(cur) = RCHLD_BLKP(cur); if (RCHLD_BLKP(cur)) PARENT_CHLDSLOTP(RCHLD_BLKP(cur)) = PARENT_CHLDSLOTP(cur); PARENT_CHLDSLOTP(cur) = PARENT_CHLDSLOTP(bp); LCHLD_BLKP(cur) = l; RCHLD_BLKP(cur) = r; PARENT_CHLDSLOTP(l) = LCHLD_BLKPREF(cur); PARENT_CHLDSLOTP(r) = RCHLD_BLKPREF(cur); } } else if (r) { *PARENT_CHLDSLOTP(bp) = r; PARENT_CHLDSLOTP(r) = PARENT_CHLDSLOTP(bp); } else if (l) { *PARENT_CHLDSLOTP(bp) = l; PARENT_CHLDSLOTP(l) = PARENT_CHLDSLOTP(bp); } else *PARENT_CHLDSLOTP(bp) = NULL; } else if (!PREV_SAMESZ_BLKP(bp)) /* Remove a free list header from the array of headers */ bins[GET_SIZE(HDRP(bp)) / DSIZE - 1] = word_to_ptr(NEXT_SAMESZ_BLKP(bp)); remove_linked_freed_block(bp); } /* Function definitions */ /* * bestfit_search - search for a block with requested size or larger in BST. */ block_ptr *bestfit_search(block_ptr *node, size_t size, int specific) { block_ptr *candidate, curr = *node; size_t curr_size; if (curr == NULL) return NULL; curr_size = GET_SIZE(HDRP(curr)); if (size < curr_size) { if (specific) return bestfit_search(LCHLD_BLKPREF(curr), size, specific); if ((candidate = bestfit_search(LCHLD_BLKPREF(curr), size, specific))) return candidate; return node; } else if (size > curr_size) return bestfit_search(RCHLD_BLKPREF(curr), size, specific); else return node; } /* * Return whether the pointer is in the heap. * May be useful for debugging. */ static inline int in_heap(const block_ptr p) { return p <= mem_heap_hi() && p >= mem_heap_lo(); } /* * Return whether the pointer is aligned. * May be useful for debugging. */ static inline int aligned(const block_ptr p) { return ((unsigned long)p % ALIGNMENT) == 0; } /* * Initialize: return -1 on error, 0 on success. */ int mm_init(void) { /* Create the initial empty heap */ if ((bins = mem_sbrk( ALIGN(fixed_bin_count * sizeof(block_ptr)) + 4 * WSIZE)) == (block_ptr)-1) return -1; memset(bins, 0, fixed_bin_count * sizeof(block_ptr)); heap_listp = (char *)ALIGN((unsigned long)(bins + fixed_bin_count)); larger_bin_root = NULL; PUTTRUNC(heap_listp, 0); /* Alignment padding */ PUTTRUNC(heap_listp + (1 * WSIZE), PACK(DSIZE, 1)); /* Prologue header */ PUTTRUNC(heap_listp + (2 * WSIZE), PACK(DSIZE, 1)); /* Prologue footer */ PUTTRUNC(heap_listp + (3 * WSIZE), PACK(0, 1)); /* Epilogue header */ heap_listp += (2 * WSIZE); SET_ALLOC(heap_listp); #ifdef DEBUG { printblock(heap_listp); checkblock(heap_listp); } operid = 0; #endif return 0; } /* * malloc */ block_ptr malloc(size_t size) { size_t asize; /* Adjusted block size */ size_t extendsize; /* Amount to extend heap if no fit */ char *bp; if (heap_listp == 0) { mm_init(); } /* Ignore spurious requests */ if (size == 0) return NULL; /* Adjust block size to include overhead and alignment reqs. */ if (size <= DSIZE) asize = 2 * DSIZE; else asize = DSIZE * ((size + (WSIZE) + (DSIZE - 1)) / DSIZE); #ifdef DEBUG printf("\nMalloc request: size = %zu, rounded to %zu \033[41;37m[ID:%d]\033[0m\n", size, asize, operid++); #endif /* Search the free list for a fit */ if ((bp = find_fit(asize)) != NULL) { #ifdef DEBUG { puts("Found fit!"); checkblock(bp); printblock(bp); } #endif place(bp, asize); return bp; } /* No fit found. Get more memory and place the block */ extendsize = MAX(asize, BLOCKSIZE); if ((bp = extend_heap(extendsize / WSIZE)) == NULL) return NULL; place(bp, asize); return bp; } /* * free */ void free(block_ptr ptr) { block_ptr tmp; size_t size; if (!ptr || !in_heap(ptr) || !aligned(ptr)) return; #ifdef DEBUG { printf("\nFree request: ptr = %p \033[41;37m[ID:%d]\033[0m\n", ptr, operid++); printblock(ptr); } #endif size = GET_SIZE(HDRP(ptr)); PUT(HDRP(ptr), PACK(size, 0)); PUT(FTRP(ptr), PACK(size, 0)); SET_UNALLOC(ptr); reset_block(ptr); tmp = coalesce(ptr); insert_free_block(tmp, GET_SIZE(HDRP(tmp))); } /* * realloc - I don't want to look at mm-naive.c */ block_ptr realloc(block_ptr oldptr, size_t size) { size_t oldsize; block_ptr newptr; /* If size == 0 then this is just free, and we return NULL. */ if (size == 0) { free(oldptr); return 0; } /* If oldptr is NULL, then this is just malloc. */ if (oldptr == NULL) { return malloc(size); } newptr = malloc(size); /* If realloc() fails the original block is left untouched */ if (!newptr) { return 0; } /* Copy the old data. */ oldsize = GET_SIZE(HDRP(oldptr)); if (size < oldsize) oldsize = size; memcpy(newptr, oldptr, oldsize); /* Free the old block. */ free(oldptr); return newptr; } /* * calloc - I don't want to look at mm-naive.c * This function is not tested by mdriver, but it is * needed to run the traces. */ block_ptr calloc(size_t nmemb, size_t size) { size_t bytes = nmemb * size; block_ptr newptr; newptr = malloc(bytes); memset(newptr, 0, bytes); return newptr; } /* * coalesce - Boundary tag coalescing. Return ptr to coalesced block */ static block_ptr coalesce(block_ptr bp) { /* * TODO Here is the bug: Do update the bins while doing this. * Tried to fix. Not sure what will happen. */ block_ptr prev, next = NEXT_BLKP(bp); /* Use GET_PREV_ALLOC to judge if prev block is allocated */ size_t prev_alloc = GET_PREV_ALLOC(bp); size_t next_alloc = GET_ALLOC(HDRP(next)); size_t size = GET_SIZE(HDRP(bp)); if (prev_alloc && next_alloc) /* Case 1 */ { return bp; } else if (prev_alloc && !next_alloc) /* Case 2 */ { remove_freed_block(next); size += GET_SIZE(HDRP(next)); PUT(HDRP(bp), PACK(size, 0)); PUT(FTRP(bp), PACK(size, 0)); } else if (!prev_alloc && next_alloc) /* Case 3 */ { prev = PREV_BLKP(bp); remove_freed_block(prev); size += GET_SIZE(HDRP(prev)); PUT(FTRP(bp), PACK(size, 0)); PUT(HDRP(prev), PACK(size, 0)); bp = prev; } else /* Case 4 */ { prev = PREV_BLKP(bp); remove_freed_block(next); remove_freed_block(prev); size += GET_SIZE(HDRP(prev)) + GET_SIZE(FTRP(next)); PUT(HDRP(prev), PACK(size, 0)); PUT(FTRP(next), PACK(size, 0)); bp = prev; } reset_block(bp); // insert_free_block(bp, size); return bp; } /* * extend_heap - Extend heap with free block and return its block pointer */ static block_ptr extend_heap(size_t words) { char *bp; size_t size; /* Allocate an even number of words to maintain alignment */ size = (words % 2) ? (words + 1) * WSIZE : words * WSIZE; if ((long)(bp = mem_sbrk(size)) == -1) return NULL; #ifdef DEBUG printf("\nExtended the heap by %zu words.\n", words); #endif /* Initialize free block header/footer and the epilogue header */ PUT(HDRP(bp), PACK(size, 0)); /* Free block header */ PUT(FTRP(bp), PACK(size, 0)); /* Free block footer */ reset_block(bp); PUT(HDRP(NEXT_BLKP(bp)), PACK(0, 1)); /* New epilogue header */ /* Coalesce if the previous block was free */ return coalesce(bp); } /* * place - Place block of asize bytes at start of free block bp * and split if remainder would be at least minimum block size */ static void place(block_ptr bp, size_t asize) { size_t csize = GET_SIZE(HDRP(bp)), delta = csize - asize; if (delta >= (2 * DSIZE)) { PUT(HDRP(bp), PACK(asize, 1)); PUT(FTRP(bp), PACK(asize, 1)); SET_ALLOC(bp); bp = NEXT_BLKP(bp); PUT(HDRP(bp), PACK(delta, 0)); PUT(FTRP(bp), PACK(delta, 0)); SET_UNALLOC(bp); reset_block(bp); insert_free_block(bp, delta); #ifdef DEBUG { printf("Block with size %zu remains a block:\n", asize); printblock(bp); } #endif } else { PUT(HDRP(bp), PACK(csize, 1)); PUT(FTRP(bp), PACK(csize, 1)); SET_ALLOC(bp); } } /* * insert_free_block - insert a block into BST or segregated free list * BLOCKSIZE should be duplicate of double word */ static void insert_free_block(block_ptr bp, size_t blocksize) { block_ptr *new = &larger_bin_root, parent = NULL; if (!IS_OVER_BST_SIZE(blocksize)) { /* Insert into segregated free list */ size_t dcount = blocksize / DSIZE; if (bins[dcount - 1]) { /* Connect it before the existing block as a new header */ NEXT_SAMESZ_BLKP(bp) = ptr_to_word(bins[dcount - 1]); PREV_SAMESZ_BLKP(bins[dcount - 1]) = ptr_to_word(bp); } PREV_SAMESZ_BLKP(bp) = WNULL; bins[dcount - 1] = bp; return; } /* Figure out where to put the new node in BST */ while (*new) { size_t curr_size = GET_SIZE(HDRP(parent = *new)); if (blocksize < curr_size) new = LCHLD_BLKPREF(parent); else if (blocksize > curr_size) new = RCHLD_BLKPREF(parent); else { /* MWHAHAHAHAHA */ block_ptr next = word_to_ptr(NEXT_SAMESZ_BLKP(bp) = NEXT_SAMESZ_BLKP(parent)); if (next) /* Connect it before the existing block as a new header */ PREV_SAMESZ_BLKP(next) = ptr_to_word(bp); NEXT_SAMESZ_BLKP(parent) = ptr_to_word(bp); PREV_SAMESZ_BLKP(bp) = ptr_to_word(parent); return; } } /* Connect this node as a child */ *new = bp; PARENT_CHLDSLOTP(bp) = new; #ifdef DEBUG { printf("Inserting a block: "); printblock(bp); } #endif } /* * find_fit - Find a fit for a block with asize bytes * asize should be duplicate of double word */ static block_ptr find_fit(size_t asize) { block_ptr curr, *blocks; size_t dcount = asize / DSIZE; if (!IS_OVER_BST_SIZE(asize)) { if (bins[dcount - 1]) { /* Found a free list of this size! */ curr = bins[dcount - 1]; bins[dcount - 1] = word_to_ptr(NEXT_SAMESZ_BLKP(curr)); remove_freed_block(curr); return curr; } /* ...not found? Proceed to BST */ } if ((blocks = bestfit_search(&larger_bin_root, asize, 0)) == NULL) /* No best-fit found...T T */ return NULL; curr = *blocks; /* Found a best-fit block! LOL */ #ifdef DEBUG if ((*blocks = word_to_ptr(NEXT_SAMESZ_BLKP(curr))) == NULL) { printf("** All blocks with size %u (request: %zu) deleted.\n", GET_SIZE(HDRP(curr)), asize); } #else /* Set the node to the next same size block if it has */ *blocks = word_to_ptr(NEXT_SAMESZ_BLKP(curr)); #endif remove_freed_block(curr); return curr; } /* * printblock - print a block for debugging */ static inline void printblock(block_ptr bp) { size_t hsize, halloc, fsize, falloc; hsize = GET_SIZE(HDRP(bp)); halloc = GET_ALLOC(HDRP(bp)); fsize = GET_SIZE(FTRP(bp)); falloc = GET_ALLOC(FTRP(bp)); if (hsize == 0) { printf("%p: EOL\n", bp); return; } if (halloc) printf("\033[43;37m%p: header: [%zu:%c:%c] footer: -\033[0m\n", bp, hsize, (GET_PREV_ALLOC(bp) ? 'a' : 'f'), (halloc ? 'a' : 'f')); else { printf("\033[42;30m%p: header: [%zu:%c:%c] footer: [%zu:%c]\033[0m", bp, hsize, (GET_PREV_ALLOC(bp) ? 'a' : 'f'), (halloc ? 'a' : 'f'), fsize, (falloc ? 'a' : 'f')); if (IS_BST_NODE(bp)) printf("\033[1;44;33m[BST Node| parent slotp: %p, l: %p, r: %p]\033[0m", PARENT_CHLDSLOTP(bp), LCHLD_BLKP(bp), RCHLD_BLKP(bp)); if (PREV_SAMESZ_BLKP(bp)) printf("\033[1;33m[PREV] %p\033[0m", word_to_ptr(PREV_SAMESZ_BLKP(bp))); putchar('\n'); } } /* * checkblock - as the name goes */ static inline void checkblock(block_ptr bp) { if (!aligned(bp)) printf("\n\033[1;47;31m## Error: %p is not doubleword aligned\033[0m\n", bp); if (!GET_ALLOC(HDRP(bp)) && (GET(HDRP(bp)) & ~0x2) != (GET(FTRP(bp)) & ~0x2)) printf("\n\033[1;47;31m## Error: header does not match footer, header: %u, footer: %u \033[0m\n", GET(HDRP(bp)), GET(FTRP(bp))); if (GET_ALLOC(HDRP(bp)) != (GET_PREV_ALLOC(NEXT_BLKP(bp)) >> 1)) printf("\n\033[1;47;31m## Error: %p allocation does not match next block's prev_alloc\033[0m\n", bp); } static void printchain(block_ptr node) { while (node) { printblock(node); printf("->"); node = word_to_ptr(NEXT_SAMESZ_BLKP(node)); } } static void printtree(block_ptr node, int depth) { int i; if (node == NULL) return; printf("BST: "); for (i = 0; i < depth; i++) putchar('-'); printchain(node); putchar('\n'); printtree(LCHLD_BLKP(node), depth + 1); printtree(RCHLD_BLKP(node), depth + 1); } static void checklist(block_ptr node) { if (node == NULL) return; if (PREV_SAMESZ_BLKP(node) && word_to_ptr(NEXT_SAMESZ_BLKP(word_to_ptr(PREV_SAMESZ_BLKP(node)))) != node) printf("\n\033[1;47;31m## Bad neighbor pointer: %p\033[0m\n", node); checklist(word_to_ptr(NEXT_SAMESZ_BLKP(node))); } static void checktree(block_ptr node) { if (node == NULL) return; if (*PARENT_CHLDSLOTP(node) != node) printf("\n\033[1;47;31m## Bad parent pointer: %p\033[0m\n", node); checklist(node); checktree(LCHLD_BLKP(node)); checktree(RCHLD_BLKP(node)); } /* * checkheap - check the heap for consistency */ void mm_checkheap(int verbose) { char *bp = heap_listp; if (verbose) printf("Heap (%p):\n", heap_listp); if ((GET_SIZE(HDRP(heap_listp)) != DSIZE) || !GET_ALLOC(HDRP(heap_listp))) printf("\n\033[1;47;31m## Bad prologue header\033[0m\n"); checkblock(heap_listp); for (bp = heap_listp; GET_SIZE(HDRP(bp)) > 0; bp = NEXT_BLKP(bp)) { if (verbose) printblock(bp); checkblock(bp); } if (verbose) { printblock(bp); { unsigned int i; for (i = 1; i <= fixed_bin_count; i++) if (bins[i - 1]) { printf("BIN #%d: size = %d ", i, i * DSIZE); checklist(bins[i - 1]); printchain(bins[i - 1]); } putchar('\n'); checktree(larger_bin_root); printtree(larger_bin_root, 0); } } if ((GET_SIZE(HDRP(bp)) != 0) || !(GET_ALLOC(HDRP(bp)))) printf("\n\033[1;47;31m## Bad epilogue header\033[0m\n"); }
/* * mm.c * * Name: LegendaryPaladin * 姓名：轩辕奇侠 * * Brief introduction: * This solution used an algorithm with segregated free list * and a binary search tree combined to maximize both space utilization * and throughput. Please note that each free list is a unique size class, * which means it only contains blocks with EXACTLY THE SAME SIZE. * * Details of binary search tree: * The BST is used to store free blocks sized larger than a specific * threshold (I set it to 40 bytes), of which each node is a header of a * free list of a same size, When searching for a free block in BST, * I applied the best-fit policy which selects the free block with * approximately minimum size among all the blocks sized larger than * requested. * * Details of segregated free list: * I set up a small array to store the headers of segregated free lists. * Each free list, as described above, has blocks with a same size. Blocks * which is not large enough to be stored in BST will be stored here. * * Block layout: * Allocated block: * * [Header: <size><prev_alloc><1>] * [Payload...] * * Large free block: * * [Header: <size><prev_alloc><0>] * [4-byte pointer to next block with same size] * [4-byte pointer to previous block with same size] * [Pointer to its left child in BST] * [Pointer to its right child in BST] * [Pointer to the pointer to itself in its parent block in BST] * [...] * [Footer: <size><0>] * * Small free block: * * [Header: <size><prev_alloc><0>] * [4-byte pointer to next block with same size] * [4-byte pointer to previous block with same size] * [...] * [Footer: <size><0>] * * Note that I omitted the footer of allocated block, instead, I * stored its allocation info in the header of next block. * * * 概述: * 本次作业，我通过分离空闲链表 + 二叉搜索树来实现空间利用率和效率的 * 最大化。注意我的每个链表都只存储一种大小的空闲块。 * * 二叉搜索树: * 二叉搜索树用于存大于某个特定阈值的块（我设为40字节），每个节点是 * 具有该大小的空闲块链表的表头。在树中查找结点的时候，我会使用“最优适配” * 策略，选择树中大于请求大小的块中近似最小的那个。 * * 分离空闲链表: * 我给分离空闲链表的表头开了个小数组，每个空闲链表同样也只存一种大小的块。 * 大小不够放到树里的块会放到这里。 * * 块布局: * 已分配块: * * [头部: <大小><上一块分配状况><1>] * [有效载荷...] * * 大的空闲块: * * [头部: <大小><上一块分配状况><0>] * [指向下一个相同大小块的4字节指针] * [指向上一个相同大小块的4字节指针] * [指向左儿子的指针] * [指向右儿子的指针] * [指向它父亲指向它的指针的指针……] * [...] * [脚部: <大小><0>] * * 小的空闲块: * * [头部: <大小><上一块分配状况><0>] * [指向下一个相同大小块的4字节指针] * [指向上一个相同大小块的4字节指针] * [...] * [脚部: <大小><0>] * * 注意我把已分配块的脚部省略了，把它的分配状态信息 * 存到了下一个块的头部。 * */ #include <assert.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> /* Other helper headers */ #include <linux/kernel.h> #include <linux/stddef.h> #include "mm.h" #include "memlib.h" /* do not change the following! */ #ifdef DRIVER /* create aliases for driver tests */ #define malloc mm_malloc #define free mm_free #define realloc mm_realloc #define calloc mm_calloc #endif /* def DRIVER */ typedef void *block_ptr; /* Global var and data structure pointers */ static char *heap_listp = 0; /* Pointer to first block */ static block_ptr larger_bin_root; /* Root of the BST which contains larger blocks */ static block_ptr *bins; /* Array of the headers of segregated free lists */ static const unsigned int fixed_bin_count = 5; /* Number of segregated free lists */ #ifdef DEBUG static int operid; #endif /* Function prototypes */ static block_ptr coalesce(block_ptr bp); static block_ptr extend_heap(size_t words); static void place(block_ptr bp, size_t asize); static void insert_free_block(block_ptr bp, size_t blocksize); static void printblock(block_ptr bp); static void checkblock(block_ptr bp); static block_ptr find_fit(size_t asize); #ifdef DEBUG static void printtree(block_ptr node, int depth); #endif /* Macros and utility inline functions */ /* Single word (4) or double word (8) alignment */ #define ALIGNMENT 8 /* Round size up to ALIGNMENT */ #define ALIGN(size) (((size) + (ALIGNMENT - 1)) & ~0x7) /* Basic constants */ #define WSIZE 4 /* Word and header/footer size (bytes) */ #define DSIZE 8 /* Doubleword size (bytes) */ #define BLOCKSIZE (1 << 6) /* Extend heap by this amount (bytes) */ #define MAX(x, y) ((x) > (y)? (x) : (y)) /* Pack a size and allocated bit into a word */ #define PACK(size, alloc) ((size) | (alloc)) /* Read and write a word at address p */ #define GET(p) (*(unsigned int *)(p)) #define PUTTRUNC(p, val) (GET(p) = (val)) /* Write header info at address p without modifying prev_alloc */ #define PUT(p, val) (GET(p) = (GET(p) & 0x2) | (val)) /* Read the size and allocated fields from address p */ #define GET_SIZE(p) (GET(p) & ~0x7) #define GET_ALLOC(p) (GET(p) & 0x1) /* Given block ptr bp, compute address of its header and footer */ #define HDRP(bp) ((char *)(bp) - WSIZE) #define FTRP(bp) ((char *)(bp) + GET_SIZE(HDRP(bp)) - DSIZE) /* Given block ptr bp, compute address of next and previous blocks */ #define NEXT_BLKP(bp) ((char *)(bp) + GET_SIZE(((char *)(bp) - WSIZE))) #define PREV_BLKP(bp) ((char *)(bp) - GET_SIZE(((char *)(bp) - DSIZE))) /* Given block ptr bp, set next block's prev_alloc */ #define SET_ALLOC(bp) (GET(HDRP(NEXT_BLKP(bp))) |= 0x2) #define SET_UNALLOC(bp) (GET(HDRP(NEXT_BLKP(bp))) &= ~0x2) /* Given block ptr bp, get prev_alloc */ #define GET_PREV_ALLOC(bp) (GET(HDRP(bp)) & 0x2) /* Given a freed block ptr bp, compute 'address' of next and previous blocks of same size */ #define NEXT_SAMESZ_BLKP(bp) (*(unsigned int *)(bp)) #define PREV_SAMESZ_BLKP(bp) (*(unsigned int *)((char *)(bp) + WSIZE)) #define WNULL 0U /* Convert 4-byte address to 8-byte address */ static inline block_ptr word_to_ptr(unsigned int w) { return ((w) == WNULL ? NULL : (block_ptr)((unsigned int)(w) + 0x800000000UL)); } /* Convert 8-byte address to 4-byte address */ static inline unsigned int ptr_to_word(block_ptr p) { return ((p) == NULL ? WNULL : (unsigned int)((unsigned long)(p) - 0x800000000UL)); } /* The following are macros for BST node blocks */ /* Check if this block is large enough to be a BST node */ #define IS_OVER_BST_SIZE(size) ((size) > DSIZE * fixed_bin_count) #define IS_BST_NODE(bp) (IS_OVER_BST_SIZE(GET_SIZE(HDRP(bp)))) /* Given BST block ptr bp, compute address of its left child or right child */ #define LCHLD_BLKPREF(bp) ((block_ptr *)((char *)(bp) + DSIZE)) #define RCHLD_BLKPREF(bp) ((block_ptr *)((char *)(bp) + DSIZE * 2)) /* Crap-like triple pointer > < */ #define PARENT_CHLDSLOTPREF(bp) ((block_ptr **)((char *)(bp) + DSIZE * 3)) #define LCHLD_BLKP(bp) (*LCHLD_BLKPREF(bp)) #define RCHLD_BLKP(bp) (*RCHLD_BLKPREF(bp)) #define PARENT_CHLDSLOTP(bp) (*PARENT_CHLDSLOTPREF(bp)) /* Reset the fields of a free block bp */ #define reset_block(bp) \ { \ NEXT_SAMESZ_BLKP(bp) = WNULL; \ PREV_SAMESZ_BLKP(bp) = WNULL; \ if (IS_BST_NODE(bp)) \ { \ LCHLD_BLKP(bp) = NULL; \ RCHLD_BLKP(bp) = NULL; \ PARENT_CHLDSLOTP(bp) = NULL; \ } \ } /* Remove bp from its free list */ #define remove_linked_freed_block(bp) \ { \ if (PREV_SAMESZ_BLKP(bp)) \ NEXT_SAMESZ_BLKP(word_to_ptr(PREV_SAMESZ_BLKP(bp))) = NEXT_SAMESZ_BLKP(bp); \ if (NEXT_SAMESZ_BLKP(bp)) \ PREV_SAMESZ_BLKP(word_to_ptr(NEXT_SAMESZ_BLKP(bp))) = PREV_SAMESZ_BLKP(bp); \ } static inline void remove_freed_block(block_ptr bp) { if (IS_BST_NODE(bp) && PARENT_CHLDSLOTP(bp)) { /* I hate deleting node. */ block_ptr l = LCHLD_BLKP(bp), r = RCHLD_BLKP(bp), cur; if ((cur = word_to_ptr(NEXT_SAMESZ_BLKP(bp)))) { PARENT_CHLDSLOTP(cur) = PARENT_CHLDSLOTP(bp); *PARENT_CHLDSLOTP(bp) = cur; LCHLD_BLKP(cur) = l; if (l) PARENT_CHLDSLOTP(l) = LCHLD_BLKPREF(cur); RCHLD_BLKP(cur) = r; if (r) PARENT_CHLDSLOTP(r) = RCHLD_BLKPREF(cur); } else if (l && r) { /* Find left-most node in right branch to replace curr */ if (!(cur = LCHLD_BLKP(r))) { /* Right child doesn't have lchild */ LCHLD_BLKP(r) = l; PARENT_CHLDSLOTP(r) = PARENT_CHLDSLOTP(bp); *PARENT_CHLDSLOTP(bp) = r; PARENT_CHLDSLOTP(l) = LCHLD_BLKPREF(r); } else { while (LCHLD_BLKP(cur)) cur = LCHLD_BLKP(cur); *PARENT_CHLDSLOTP(bp) = cur; *PARENT_CHLDSLOTP(cur) = RCHLD_BLKP(cur); if (RCHLD_BLKP(cur)) PARENT_CHLDSLOTP(RCHLD_BLKP(cur)) = PARENT_CHLDSLOTP(cur); PARENT_CHLDSLOTP(cur) = PARENT_CHLDSLOTP(bp); LCHLD_BLKP(cur) = l; RCHLD_BLKP(cur) = r; PARENT_CHLDSLOTP(l) = LCHLD_BLKPREF(cur); PARENT_CHLDSLOTP(r) = RCHLD_BLKPREF(cur); } } else if (r) { *PARENT_CHLDSLOTP(bp) = r; PARENT_CHLDSLOTP(r) = PARENT_CHLDSLOTP(bp); } else if (l) { *PARENT_CHLDSLOTP(bp) = l; PARENT_CHLDSLOTP(l) = PARENT_CHLDSLOTP(bp); } else *PARENT_CHLDSLOTP(bp) = NULL; } else if (!PREV_SAMESZ_BLKP(bp)) /* Remove a free list header from the array of headers */ bins[GET_SIZE(HDRP(bp)) / DSIZE - 1] = word_to_ptr(NEXT_SAMESZ_BLKP(bp)); remove_linked_freed_block(bp); } /* Function definitions */ /* * bestfit_search - search for a block with requested size or larger in BST. */ block_ptr *bestfit_search(block_ptr *node, size_t size, int specific) { block_ptr *candidate, curr = *node; size_t curr_size; if (curr == NULL) return NULL; curr_size = GET_SIZE(HDRP(curr)); if (size < curr_size) { if (specific) return bestfit_search(LCHLD_BLKPREF(curr), size, specific); if ((candidate = bestfit_search(LCHLD_BLKPREF(curr), size, specific))) return candidate; return node; } else if (size > curr_size) return bestfit_search(RCHLD_BLKPREF(curr), size, specific); else return node; } /* * Return whether the pointer is in the heap. * May be useful for debugging. */ static inline int in_heap(const block_ptr p) { return p <= mem_heap_hi() && p >= mem_heap_lo(); } /* * Return whether the pointer is aligned. * May be useful for debugging. */ static inline int aligned(const block_ptr p) { return ((unsigned long)p % ALIGNMENT) == 0; } /* * Initialize: return -1 on error, 0 on success. */ int mm_init(void) { /* Create the initial empty heap */ if ((bins = mem_sbrk( ALIGN(fixed_bin_count * sizeof(block_ptr)) + 4 * WSIZE)) == (block_ptr)-1) return -1; memset(bins, 0, fixed_bin_count * sizeof(block_ptr)); heap_listp = (char *)ALIGN((unsigned long)(bins + fixed_bin_count)); larger_bin_root = NULL; PUTTRUNC(heap_listp, 0); /* Alignment padding */ PUTTRUNC(heap_listp + (1 * WSIZE), PACK(DSIZE, 1)); /* Prologue header */ PUTTRUNC(heap_listp + (2 * WSIZE), PACK(DSIZE, 1)); /* Prologue footer */ PUTTRUNC(heap_listp + (3 * WSIZE), PACK(0, 1)); /* Epilogue header */ heap_listp += (2 * WSIZE); SET_ALLOC(heap_listp); #ifdef DEBUG { printblock(heap_listp); checkblock(heap_listp); } operid = 0; #endif return 0; } /* * malloc */ block_ptr malloc(size_t size) { size_t asize; /* Adjusted block size */ size_t extendsize; /* Amount to extend heap if no fit */ char *bp; if (heap_listp == 0) { mm_init(); } /* Ignore spurious requests */ if (size == 0) return NULL; /* Adjust block size to include overhead and alignment reqs. */ if (size <= DSIZE) asize = 2 * DSIZE; else asize = DSIZE * ((size + (WSIZE) + (DSIZE - 1)) / DSIZE); #ifdef DEBUG printf("\nMalloc request: size = %zu, rounded to %zu \033[41;37m[ID:%d]\033[0m\n", size, asize, operid++); #endif /* Search the free list for a fit */ if ((bp = find_fit(asize)) != NULL) { #ifdef DEBUG { puts("Found fit!"); checkblock(bp); printblock(bp); } #endif place(bp, asize); return bp; } /* No fit found. Get more memory and place the block */ extendsize = MAX(asize, BLOCKSIZE); if ((bp = extend_heap(extendsize / WSIZE)) == NULL) return NULL; place(bp, asize); return bp; } /* * free */ void free(block_ptr ptr) { block_ptr tmp; size_t size; if (!ptr || !in_heap(ptr) || !aligned(ptr)) return; #ifdef DEBUG { printf("\nFree request: ptr = %p \033[41;37m[ID:%d]\033[0m\n", ptr, operid++); printblock(ptr); } #endif size = GET_SIZE(HDRP(ptr)); PUT(HDRP(ptr), PACK(size, 0)); PUT(FTRP(ptr), PACK(size, 0)); SET_UNALLOC(ptr); reset_block(ptr); tmp = coalesce(ptr); insert_free_block(tmp, GET_SIZE(HDRP(tmp))); } /* * realloc - I don't want to look at mm-naive.c */ block_ptr realloc(block_ptr oldptr, size_t size) { size_t oldsize; block_ptr newptr; /* If size == 0 then this is just free, and we return NULL. */ if (size == 0) { free(oldptr); return 0; } /* If oldptr is NULL, then this is just malloc. */ if (oldptr == NULL) { return malloc(size); } newptr = malloc(size); /* If realloc() fails the original block is left untouched */ if (!newptr) { return 0; } /* Copy the old data. */ oldsize = GET_SIZE(HDRP(oldptr)); if (size < oldsize) oldsize = size; memcpy(newptr, oldptr, oldsize); /* Free the old block. */ free(oldptr); return newptr; } /* * calloc - I don't want to look at mm-naive.c * This function is not tested by mdriver, but it is * needed to run the traces. */ block_ptr calloc(size_t nmemb, size_t size) { size_t bytes = nmemb * size; block_ptr newptr; newptr = malloc(bytes); memset(newptr, 0, bytes); return newptr; } /* * coalesce - Boundary tag coalescing. Return ptr to coalesced block */ static block_ptr coalesce(block_ptr bp) { /* * TODO Here is the bug: Do update the bins while doing this. * Tried to fix. Not sure what will happen. */ block_ptr prev, next = NEXT_BLKP(bp); /* Use GET_PREV_ALLOC to judge if prev block is allocated */ size_t prev_alloc = GET_PREV_ALLOC(bp); size_t next_alloc = GET_ALLOC(HDRP(next)); size_t size = GET_SIZE(HDRP(bp)); if (prev_alloc && next_alloc) /* Case 1 */ { return bp; } else if (prev_alloc && !next_alloc) /* Case 2 */ { remove_freed_block(next); size += GET_SIZE(HDRP(next)); PUT(HDRP(bp), PACK(size, 0)); PUT(FTRP(bp), PACK(size, 0)); } else if (!prev_alloc && next_alloc) /* Case 3 */ { prev = PREV_BLKP(bp); remove_freed_block(prev); size += GET_SIZE(HDRP(prev)); PUT(FTRP(bp), PACK(size, 0)); PUT(HDRP(prev), PACK(size, 0)); bp = prev; } else /* Case 4 */ { prev = PREV_BLKP(bp); remove_freed_block(next); remove_freed_block(prev); size += GET_SIZE(HDRP(prev)) + GET_SIZE(FTRP(next)); PUT(HDRP(prev), PACK(size, 0)); PUT(FTRP(next), PACK(size, 0)); bp = prev; } reset_block(bp); // insert_free_block(bp, size); return bp; } /* * extend_heap - Extend heap with free block and return its block pointer */ static block_ptr extend_heap(size_t words) { char *bp; size_t size; /* Allocate an even number of words to maintain alignment */ size = (words % 2) ? (words + 1) * WSIZE : words * WSIZE; if ((long)(bp = mem_sbrk(size)) == -1) return NULL; #ifdef DEBUG printf("\nExtended the heap by %zu words.\n", words); #endif /* Initialize free block header/footer and the epilogue header */ PUT(HDRP(bp), PACK(size, 0)); /* Free block header */ PUT(FTRP(bp), PACK(size, 0)); /* Free block footer */ reset_block(bp); PUT(HDRP(NEXT_BLKP(bp)), PACK(0, 1)); /* New epilogue header */ /* Coalesce if the previous block was free */ return coalesce(bp); } /* * place - Place block of asize bytes at start of free block bp * and split if remainder would be at least minimum block size */ static void place(block_ptr bp, size_t asize) { size_t csize = GET_SIZE(HDRP(bp)), delta = csize - asize; if (delta >= (2 * DSIZE)) { PUT(HDRP(bp), PACK(asize, 1)); PUT(FTRP(bp), PACK(asize, 1)); SET_ALLOC(bp); bp = NEXT_BLKP(bp); PUT(HDRP(bp), PACK(delta, 0)); PUT(FTRP(bp), PACK(delta, 0)); SET_UNALLOC(bp); reset_block(bp); insert_free_block(bp, delta); #ifdef DEBUG { printf("Block with size %zu remains a block:\n", asize); printblock(bp); } #endif } else { PUT(HDRP(bp), PACK(csize, 1)); PUT(FTRP(bp), PACK(csize, 1)); SET_ALLOC(bp); } } /* * insert_free_block - insert a block into BST or segregated free list * BLOCKSIZE should be duplicate of double word */ static void insert_free_block(block_ptr bp, size_t blocksize) { block_ptr *new = &larger_bin_root, parent = NULL; if (!IS_OVER_BST_SIZE(blocksize)) { /* Insert into segregated free list */ size_t dcount = blocksize / DSIZE; if (bins[dcount - 1]) { /* Connect it before the existing block as a new header */ NEXT_SAMESZ_BLKP(bp) = ptr_to_word(bins[dcount - 1]); PREV_SAMESZ_BLKP(bins[dcount - 1]) = ptr_to_word(bp); } PREV_SAMESZ_BLKP(bp) = WNULL; bins[dcount - 1] = bp; return; } /* Figure out where to put the new node in BST */ while (*new) { size_t curr_size = GET_SIZE(HDRP(parent = *new)); if (blocksize < curr_size) new = LCHLD_BLKPREF(parent); else if (blocksize > curr_size) new = RCHLD_BLKPREF(parent); else { /* MWHAHAHAHAHA */ block_ptr next = word_to_ptr(NEXT_SAMESZ_BLKP(bp) = NEXT_SAMESZ_BLKP(parent)); if (next) /* Connect it before the existing block as a new header */ PREV_SAMESZ_BLKP(next) = ptr_to_word(bp); NEXT_SAMESZ_BLKP(parent) = ptr_to_word(bp); PREV_SAMESZ_BLKP(bp) = ptr_to_word(parent); return; } } /* Connect this node as a child */ *new = bp; PARENT_CHLDSLOTP(bp) = new; #ifdef DEBUG { printf("Inserting a block: "); printblock(bp); } #endif } /* * find_fit - Find a fit for a block with asize bytes * asize should be duplicate of double word */ static block_ptr find_fit(size_t asize) { block_ptr curr, *blocks; size_t dcount = asize / DSIZE; if (!IS_OVER_BST_SIZE(asize)) { if (bins[dcount - 1]) { /* Found a free list of this size! */ curr = bins[dcount - 1]; bins[dcount - 1] = word_to_ptr(NEXT_SAMESZ_BLKP(curr)); remove_freed_block(curr); return curr; } /* ...not found? Proceed to BST */ } if ((blocks = bestfit_search(&larger_bin_root, asize, 0)) == NULL) /* No best-fit found...T T */ return NULL; curr = *blocks; /* Found a best-fit block! LOL */ #ifdef DEBUG if ((*blocks = word_to_ptr(NEXT_SAMESZ_BLKP(curr))) == NULL) { printf("** All blocks with size %u (request: %zu) deleted.\n", GET_SIZE(HDRP(curr)), asize); } #else /* Set the node to the next same size block if it has */ *blocks = word_to_ptr(NEXT_SAMESZ_BLKP(curr)); #endif remove_freed_block(curr); return curr; } /* * printblock - print a block for debugging */ static inline void printblock(block_ptr bp) { size_t hsize, halloc, fsize, falloc; hsize = GET_SIZE(HDRP(bp)); halloc = GET_ALLOC(HDRP(bp)); fsize = GET_SIZE(FTRP(bp)); falloc = GET_ALLOC(FTRP(bp)); if (hsize == 0) { printf("%p: EOL\n", bp); return; } if (halloc) printf("\033[43;37m%p: header: [%zu:%c:%c] footer: -\033[0m\n", bp, hsize, (GET_PREV_ALLOC(bp) ? 'a' : 'f'), (halloc ? 'a' : 'f')); else { printf("\033[42;30m%p: header: [%zu:%c:%c] footer: [%zu:%c]\033[0m", bp, hsize, (GET_PREV_ALLOC(bp) ? 'a' : 'f'), (halloc ? 'a' : 'f'), fsize, (falloc ? 'a' : 'f')); if (IS_BST_NODE(bp)) printf("\033[1;44;33m[BST Node| parent slotp: %p, l: %p, r: %p]\033[0m", PARENT_CHLDSLOTP(bp), LCHLD_BLKP(bp), RCHLD_BLKP(bp)); if (PREV_SAMESZ_BLKP(bp)) printf("\033[1;33m[PREV] %p\033[0m", word_to_ptr(PREV_SAMESZ_BLKP(bp))); putchar('\n'); } } /* * checkblock - as the name goes */ static inline void checkblock(block_ptr bp) { if (!aligned(bp)) printf("\n\033[1;47;31m## Error: %p is not doubleword aligned\033[0m\n", bp); if (!GET_ALLOC(HDRP(bp)) && (GET(HDRP(bp)) & ~0x2) != (GET(FTRP(bp)) & ~0x2)) printf("\n\033[1;47;31m## Error: header does not match footer, header: %u, footer: %u \033[0m\n", GET(HDRP(bp)), GET(FTRP(bp))); if (GET_ALLOC(HDRP(bp)) != (GET_PREV_ALLOC(NEXT_BLKP(bp)) >> 1)) printf("\n\033[1;47;31m## Error: %p allocation does not match next block's prev_alloc\033[0m\n", bp); } static void printchain(block_ptr node) { while (node) { printblock(node); printf("->"); node = word_to_ptr(NEXT_SAMESZ_BLKP(node)); } } static void printtree(block_ptr node, int depth) { int i; if (node == NULL) return; printf("BST: "); for (i = 0; i < depth; i++) putchar('-'); printchain(node); putchar('\n'); printtree(LCHLD_BLKP(node), depth + 1); printtree(RCHLD_BLKP(node), depth + 1); } static void checklist(block_ptr node) { if (node == NULL) return; if (PREV_SAMESZ_BLKP(node) && word_to_ptr(NEXT_SAMESZ_BLKP(word_to_ptr(PREV_SAMESZ_BLKP(node)))) != node) printf("\n\033[1;47;31m## Bad neighbor pointer: %p\033[0m\n", node); checklist(word_to_ptr(NEXT_SAMESZ_BLKP(node))); } static void checktree(block_ptr node) { if (node == NULL) return; if (*PARENT_CHLDSLOTP(node) != node) printf("\n\033[1;47;31m## Bad parent pointer: %p\033[0m\n", node); checklist(node); checktree(LCHLD_BLKP(node)); checktree(RCHLD_BLKP(node)); } /* * checkheap - check the heap for consistency */ void mm_checkheap(int verbose) { char *bp = heap_listp; if (verbose) printf("Heap (%p):\n", heap_listp); if ((GET_SIZE(HDRP(heap_listp)) != DSIZE) || !GET_ALLOC(HDRP(heap_listp))) printf("\n\033[1;47;31m## Bad prologue header\033[0m\n"); checkblock(heap_listp); for (bp = heap_listp; GET_SIZE(HDRP(bp)) > 0; bp = NEXT_BLKP(bp)) { if (verbose) printblock(bp); checkblock(bp); } if (verbose) { printblock(bp); { unsigned int i; for (i = 1; i <= fixed_bin_count; i++) if (bins[i - 1]) { printf("BIN #%d: size = %d ", i, i * DSIZE); checklist(bins[i - 1]); printchain(bins[i - 1]); } putchar('\n'); checktree(larger_bin_root); printtree(larger_bin_root, 0); } } if ((GET_SIZE(HDRP(bp)) != 0) || !(GET_ALLOC(HDRP(bp)))) printf("\n\033[1;47;31m## Bad epilogue header\033[0m\n"); }
最终成绩如图：
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