Differences and relationships between page cache and buffer cache

Page cache and Buffer
Cache has always been a confusing concept. Many people on the Internet are arguing about the differences between the two caches, at the end of the discussion, there has never been a unified and correct conclusion. During the period of my work, page
Cache and Buffer
The concept of cache has plagued me, but after careful analysis, these two concepts are actually very clear. If we can understand the nature of these two caches, we may be more comfortable in analyzing Io problems.
Page
The cache is actually for the file system. It is the File Cache, and the data at the file level will be cached to the page.
Cache. The logic layer of the file needs to be mapped to the actual physical disk. This ing relationship is completed by the file system. When the page
When cache data needs to be refreshed, the data in the page cache is handed over to the buffer
Cache, but this kind of processing becomes very simple after the kernel version 2.6, and there is no real cache operation.
Buffer
The cache is the cache for disk blocks, that is, if no file system is available, data directly operated on the disk will be cached to the buffer.
Cache. For example, the metadata of the file system is cached in the buffer cache.
In short, page cache is used to cache file data, Buffer
Cache is used to cache disk data. If a file system is used to operate on a file, the data is cached on the page.
Cache. If you directly use dd and other tools to read and write the disk, the data will be cached in the buffer cache.