windows Windows下如何刷新磁盘读取缓存？
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How to flush the disk read cache under Windows?
提问by sorin
Possible Duplicate:
How to invalidate the file system cache?
可能的重复：
如何使文件系统缓存无效？
In order to be able to so some benchmarks I need to cleanup Windows disk readcache. How can I do this?
为了能够进行一些基准测试，我需要清理 Windows 磁盘读取缓存。我怎样才能做到这一点？
In fact I want to compare if loading a big Unicode file (UTF-8 or UTF-16) from disk is faster or not, considering that in memory I do keep UTF-16.
事实上，我想比较从磁盘加载一个大的 Unicode 文件（UTF-8 或 UTF-16）是否更快，考虑到在内存中我确实保留了 UTF-16。
I know that it should be no significant difference but in order to benchmark it I need to be sure that that file is not cached - I need to see if size on disk has more or less impact than decoding the file.
我知道它应该没有显着差异，但为了对其进行基准测试，我需要确保该文件没有被缓存 - 我需要查看磁盘上的大小是否比解码文件具有更多或更少的影响。
采纳答案by sorin
The only solution I found so far was http://chadaustin.me/2009/04/flushing-disk-cache/but this ones takes too much time so I hope we'll find a better one.
到目前为止，我找到的唯一解决方案是http://chadaustin.me/2009/04/flushing-disk-cache/，但这个解决方案需要太多时间，所以我希望我们能找到更好的解决方案。
回答by snemarch
AFAIK, it's unfortunately not possible to discardthe readcache under Windows.I spent some time looking into this some years ago, and only found out how to flushthe writecache.
据我所知，这是不幸的是不可能放弃的读取Windows下的高速缓存。我花了一些时间寻找到这个几年前，只发现了如何刷新了写入缓存。
As I see it, you have three options, unless somebody else has found some magic:
在我看来，你有三个选择，除非其他人发现了一些魔法：
- If possible, do your read file I/O in unbuffered mode.
- Each time you want to benchmark, create a new copy of the test data specifying unbuffered mode when creating the new copy (this shouldkeep the copy out of read cache, but I haven't tested).
- Allocate enough memory that windows has to discard the disk cache (ugh!).
- 如果可能，请在无缓冲模式下执行读取文件 I/O。
- 每次要进行基准测试时，请在创建新副本时创建指定无缓冲模式的测试数据的新副本（这应该使副本不在读取缓存中，但我还没有测试过）。
- 分配足够的内存，Windows 必须丢弃磁盘缓存（呃！）。
EDIT: it is indeed possible to flush the read cache, at least on Vista and later: Disable or flush page cache on Windows. It requires a call to the undocumented NtSetSystemInformationNT API, though. Also, for a single file, read cache can be flushed simply by opening the file with FILE_FLAG_NO_BUFFERINGspecified and closing the handle again.
编辑：确实可以刷新读取缓存，至少在 Vista 及更高版本上：禁用或刷新 Windows 上的页面缓存。但是，它需要调用未记录的NtSetSystemInformationNT API。此外，对于单个文件，可以通过打开FILE_FLAG_NO_BUFFERING指定的文件并再次关闭句柄来刷新读取缓存。
回答by Jeff Grills
Someone from Microsoft helped me out with this a few years ago (back in the days of Windows XP) and gave me a solution that met my needs at the time. I already had two drives in my machine, and what I needed to test was already on the D drive, and fortunately I didn't need to keep any files open on my D drive when I wanted to flush the cache. From the Windows Disk Management interface, I could change my D: drive letter to another letter, and then back again, and the D drive would perform as if had a cold cache in the OS.
几年前（回到 Windows XP 时代），Microsoft 的某个人帮助我解决了这个问题，并给了我一个满足我当时需求的解决方案。我的机器里已经有两个驱动器了，我需要测试的东西已经在D盘上了，幸运的是，当我想刷新缓存时，我不需要在我的D盘上保持任何文件打开。从 Windows 磁盘管理界面，我可以将我的 D: 盘符更改为另一个盘符，然后再返回，D 盘会像操作系统中的冷缓存一样运行。
