Short answer:
Cachedis the size of the page cache.
Buffers is the size of in-memory block I/O buffers.
Cached matters;
Buffers is largely irrelevant.
Long answer:
Cached is the size of the Linux page cache, minus the memory in the swap cache, which is represented by
SwapCached(thus the total page cache size is
Cached+
SwapCached). Linux performs all file I/O throughthe page cache. Writes are implemented as simply marking as dirty the corresponding pages in the page cache; the flusher threads then periodically write back to disk any dirty pages. Reads are implemented by returning thedata from the page cache; if the data is not yet in the cache, it is firstpopulated. On a modern Linux system,
Cached can easily be several gigabytes. It will shrink only in response to memory pressure. The system will purge the page cache along with swapping data out to disk to make available more memory as needed.
Buffers are in-memory block I/O buffers. They are relatively short-lived. Prior to Linux kernel version 2.4, Linux had separate page and buffer caches. Since 2.4, the page and buffer cache are unified and
Buffersis raw disk blocksnot represented in the page cache—i.e., not file data. The
Buffers metric isthus of minimal importance. On most systems,
Buffers is often only tens ofmegabytes.
________________________________________________________________________________________________
转播
