网站布局,企业网站建设经验分享,网站备案 厦门,有服务器和网站代码了 怎么建站/proc/sys/vm/drop_caches 是 Linux 中的一个特殊文件#xff0c;允许用户释放系统内存中的各种缓存。让我们深入了解一下这项功能的细节#xff1a; The /proc/sys/vm/drop_caches is a special file in Linux that allows users to free up various caches in the systems …
/proc/sys/vm/drop_caches 是 Linux 中的一个特殊文件允许用户释放系统内存中的各种缓存。让我们深入了解一下这项功能的细节 The /proc/sys/vm/drop_caches is a special file in Linux that allows users to free up various caches in the systems memory. Lets dive into the details of this feature: Overview /proc/sys/vm/drop_caches 是 Linux 内核提供的一种机制用于手动释放内存中的页面缓存、目录项缓存和 inodes。这在测试或需要快速释放内存的情况下非常有用。 /proc/sys/vm/drop_caches is a mechanism provided by the Linux kernel to manually free up pagecache, dentries, and inodes from memory. This can be useful for testing purposes or in situations where you need to free up memory quickly. Functionality drop_caches 参数允许用户指示内核释放不同类型的缓存 The drop_caches parameter allows users to instruct the kernel to free different types of caches: 1. 页面缓存 这是文件内容的缓存。 2. Dentries 这是目录条目缓存。 3. Inodes 这些是包含文件元数据的数据结构。 1. Pagecache: This is the cache for file contents. 2. Dentries: These are directory entry caches. 3. Inodes: These are data structures containing metadata about files. Usage 要使用 drop_caches需要在文件中写入一个特定值 To use drop_caches, you write a specific value to the file: 1. Echo 1仅释放页面缓存。 2. Echo 2释放目录项缓存和 inodes。 3. Echo 3: 释放页面缓存、目录项缓存和 inodes。 1. Echo 1: Frees pagecache only. 2. Echo 2: Frees dentries and inodes. 3. Echo 3: Frees pagecache, dentries, and inodes. 例如要释放所有缓存可以使用 For example, to free all caches, you would use: echo 3 /proc/sys/vm/drop_caches Important Considerations 重要考虑因素 1. 非破坏性操作 此操作为非破坏性操作不会释放任何脏对象已修改但尚未写入磁盘的对象。 1. Non-destructive Operation: This operation is non-destructive and will not free any dirty objects (those that have been modified but not yet written to disk). 2. 丢弃前同步 建议在删除缓存前运行 “同步”以确保所有脏对象都写入磁盘。 2. Sync Before Dropping: Its recommended to run sync before dropping caches to ensure all dirty objects are written to disk. 3. 性能影响 使用 drop_caches 可能会导致性能问题因为它会丢弃可能需要重新创建的缓存对象从而可能导致大量的 I/O 和 CPU 占用。 3. Performance Impact: Using drop_caches can cause performance problems as it discards cached objects that may need to be recreated, potentially causing significant I/O and CPU usage. 4. 不适合常规使用 由于可能影响性能不建议在测试或调试环境之外使用 drop_caches。 4. Not for Regular Use: Due to potential performance impacts, using drop_caches is not recommended outside of testing or debugging environments. 5. 自动回收 当系统其他地方需要内存时内核会自动回收这些对象因此通常不需要人工干预。 5. Automatic Reclamation: The kernel automatically reclaims these objects when memory is needed elsewhere in the system, so manual intervention is usually unnecessary. 6. 信息消息 使用该文件时您可能会在内核日志中看到信息消息。这些信息并不表示系统有任何问题。 6. Informational Messages: You may see informational messages in your kernel log when this file is used. These messages do not indicate any problem with your system. Behavior After Dropping Caches 删除缓存后 1. 作为正常运行的一部分系统会立即重新开始缓存。 2. /proc/sys/vm/drop_caches 中的值会自动重置为 0。 After dropping caches: 1. The system immediately starts caching again as part of its normal operation. 2. The value in /proc/sys/vm/drop_caches automatically resets to 0. Use Cases 虽然不建议经常使用但 drop_caches 在特定情况下还是很有用的 1. 测试 需要使用低缓存进行基准测试或性能测试时。 2. 调试 隔离与缓存相关的问题。 3. 内存管理 在极少数情况下需要快速释放内存但应谨慎处理。 While not recommended for regular use, drop_caches can be useful in specific scenarios: 1. Testing: When you need to start with a cold cache for benchmarking or performance testing. 2. Debugging: To isolate issues related to caching. 3. Memory Management: In rare cases where you need to quickly free up memory, though this should be approached with caution. Alternative Approaches 对于大多数系统来说最好让内核自动管理缓存。如果内存一直不足可以考虑 1. 为系统添加更多内存。 2. 调整其他内存管理参数。 3. 优化系统上运行的应用程序。 For most systems, its better to let the kernel manage caches automatically. If youre consistently running low on memory, consider: 1. Adding more RAM to the system. 2. Adjusting other memory management parameters. 3. Optimizing the applications running on the system. 总之虽然 /proc/sys/vm/drop_caches 提供了在 Linux 中手动释放各种缓存的方法但应谨慎使用并主要用于测试或调试目的。对于正常的系统操作最好还是依靠内核内置的内存管理功能。 In conclusion, while /proc/sys/vm/drop_caches provides a way to manually free up various caches in Linux, it should be used judiciously and primarily for testing or debugging purposes. For normal system operation, its generally best to rely on the kernels built-in memory management capabilities. 资料来源: [1] Setting /proc/sys/vm/drop_caches to clear cache, https://unix.stackexchange.com/questions/17936/setting-proc-sys-vm-drop-caches-to-clear-cache [2] Drop_Caches - linux-mm.org Wiki, Drop_Caches - linux-mm.org Wiki [3] Freeing page cache using echo 3 /proc/sys/vm/drop_caches ..., https://askubuntu.com/questions/609226/freeing-page-cache-using-echo-3-proc-sys-vm-drop-caches-doesnt-work [4] Why does drop_caches increase available memory - Server Fault, https://serverfault.com/questions/1099933/why-does-drop-caches-increase-available-memory
