Notes about linux DAX
本文将mark下DAX(Direct Access)相关notes。
What
Direct Access (DAX) enables direct access to files stored in persistent memory or on a block device. Without DAX support in a file system, the page cache is generally used to buffer reads and writes to files, and requires an extra copy operation.
DAX removes the extra copy operation by performing reads and writes directly to the storage device.
Why
The page cache is usually used to buffer reads and writes to files. It is also used to provide the pages which are mapped into userspace by a call to mmap.
For block devices that are memory-like, the page cache pages would be unnecessary copies of the original storage. The DAX code removes the extra copy by performing reads and writes directly to the storage device. For file mappings, the storage device is mapped directly into userspace.
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