页面置换算法操作系统查看页面调度的代码

页面置换算法在操作系统中是一种内存管理策略，用于解决有限内存空间和大量可访问数据之间的冲突。常见的页面置换算法有简单选择替换（LRU - Least Recently Used）、先进先出（FIFO - First In First Out）、最近最久未使用（LFU - Least Frequently Used）等。

查看具体的页面调度代码取决于使用的编程语言和操作系统内核。这里提供一个简化的示例，假设使用Python模拟LRU页面置换：

class Page:
    def __init__(self, id):
        self.id = id
        self.access_count = 0

class LRUPageCache:
    def __init__(self, capacity):
        self.capacity = capacity
        self.pages = {i: Page(i) for i in range(capacity)}
        self.lru_list = [None] * capacity  # 使用双向链表模拟LRU顺序

    def get(self, id):
        if id not in self.pages:
            return None
        page = self.pages[id]
        page.access_count += 1
        self._insert_in_lru(page)
        return page

    def put(self, id):
        if id in self.pages:
            self.pages[id].access_count = 1
            self._remove_from_lru(id)
        else:
            if len(self.pages) >= self.capacity:
                evicted_id = self._evict()
                del self.pages[evicted_id]
        self.pages[id] = Page(id)
        self._insert_in_lru(self.pages[id])

    def _insert_in_lru(self, page):
        index = page.id % self.capacity
        page.next = self.lru_list[index + 1]
        page.prev = self.lru_list[index]
        if self.lru_list[index] is not None:
            self.lru_list[index].prev = page
        self.lru_list[index] = page

    def _remove_from_lru(self, id):
        page = self.pages[id]
        index = page.id % self.capacity
        if page.prev is not None:
            page.prev.next = page.next
        elif page.next is not None:
            page.next.prev = page.prev
        else:
            assert self.lru_list[0] is not None and self.lru_list[self.capacity - 1] is not None
            page.next = self.lru_list[0]
            page.prev = self.lru_list[self.capacity - 1]
            self.lru_list[self.capacity - 1].next = page
        self.lru_list[index] = None

    def _evict(self):
        # 这里是一个简化版本，通常会根据某种淘汰策略选择，比如访问计数最少
        evicted_id = min(self.pages.keys(), key=lambda k: self.pages[k].access_count)
        return evicted_id

# 示例用法
cache = LRUPageCache(4)
cache.put(1)
cache.get(1)
cache.put(2)
cache.put(3)
cache.get(2)  # 2在LRU链首，会被替换掉1

请注意这只是一个简化版本，实际生产环境中的页框调度可能会更复杂，涉及到硬件层面的操作，并且内核级实现通常会包含更多性能优化措施。