138 lines
4.3 KiB
Python
138 lines
4.3 KiB
Python
from dataclasses import dataclass, field
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from typing import List, Dict, Optional, Tuple
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import math
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class MemoryAllocationStrategy:
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"""
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内存分配策略
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"""
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FIRST_FIT = 'first_fit' # 首次适应算法
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BEST_FIT = 'best_fit' # 最佳适应算法
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WORST_FIT = 'worst_fit' # 最坏适应算法
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@dataclass
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class MemoryBlock:
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"""
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表示内存块
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"""
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start_address: int # 起始地址
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size: int # 内存块大小
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is_free: bool = True # 是否空闲
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process_id: Optional[int] = None # 占用该内存块的进程ID
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class MemoryManager:
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"""
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管理内存分配、释放和虚拟内存
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"""
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def __init__(
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self,
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total_memory: int = 1024 * 1024, # 默认1MB
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page_size: int = 4096, # 4KB页大小
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allocation_strategy: str = MemoryAllocationStrategy.FIRST_FIT
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):
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self.total_memory = total_memory # 总内存大小
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self.page_size = page_size # 页大小
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self.allocation_strategy = allocation_strategy # 分配策略
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# 内存块映射
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self.memory_map: List[MemoryBlock] = [
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MemoryBlock(0, total_memory)
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]
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# 虚拟内存的页表
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self.page_table: Dict[int, List[Tuple[int, bool]]] = {}
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# 缺页跟踪
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self.total_memory_accesses = 0
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self.page_faults = 0
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def allocate_memory(
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self,
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process_id: int,
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memory_size: int
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) -> Optional[int]:
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"""
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为进程分配内存
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:param process_id: 请求内存的进程ID
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:param memory_size: 要分配的内存大小
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:return: 分配的内存起始地址，分配失败返回None
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"""
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# 根据分配策略选择内存分配方法
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allocation_method = {
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MemoryAllocationStrategy.FIRST_FIT: self._first_fit_allocation,
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MemoryAllocationStrategy.BEST_FIT: self._best_fit_allocation,
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MemoryAllocationStrategy.WORST_FIT: self._worst_fit_allocation
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}.get(self.allocation_strategy)
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return allocation_method(process_id, memory_size)
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def _first_fit_allocation(
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self,
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process_id: int,
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memory_size: int
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) -> Optional[int]:
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"""
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首次适应内存分配策略
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:param process_id: 请求内存的进程ID
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:param memory_size: 要分配的内存大小
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:return: 分配的内存起始地址，分配失败返回None
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"""
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for i, block in enumerate(self.memory_map):
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if block.is_free and block.size >= memory_size:
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# 如果内存块大于请求大小，则分割块
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if block.size > memory_size:
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new_block = MemoryBlock(
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block.start_address + memory_size,
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block.size - memory_size
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)
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self.memory_map.insert(i + 1, new_block)
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# 更新原内存块
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block.is_free = False
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block.process_id = process_id
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block.size = memory_size
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return block.start_address
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return None
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def _best_fit_allocation(
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self,
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process_id: int,
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memory_size: int
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) -> Optional[int]:
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"""
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最佳适应内存分配策略
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:param process_id: 请求内存的进程ID
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:param memory_size: 要分配的内存大小
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:return: 分配的内存起始地址，分配失败返回None
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"""
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best_block = None
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best_block_index = -1
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smallest_difference = float('inf')
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for i, block in enumerate(self.memory_map):
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if block.is_free and block.size >= memory_size:
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difference = block.size - memory_size
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if difference < smallest_difference:
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smallest_difference = difference
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best_block = block
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best_block_index = i
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if best_block:
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# 如果内存块大于请求大小，则分割块
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if best_block.size > memory_size:
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new_block = MemoryBlock(
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best_block.start_address + memory_size,
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best_block.size - memory_size
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)
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self.memory_map.insert(best_block_index + 1, new_block)
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# 更 |