cat /proc/meminfo
MemTotal: 8162388 kB
MemFree: 86004 kB
Buffers: 56432 kB
Cached: 1141924 kB
SwapCached: 800992 kB
Active: 6090024 kB
Inactive: 1857208 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 8162388 kB
LowFree: 86004 kB
SwapTotal: 2096472 kB
SwapFree: 1048264 kB
MemTotal: 8162388 kB
MemFree: 86004 kB
Buffers: 56432 kB
Cached: 1141924 kB
SwapCached: 800992 kB
Active: 6090024 kB
Inactive: 1857208 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 8162388 kB
LowFree: 86004 kB
SwapTotal: 2096472 kB
SwapFree: 1048264 kB
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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.
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.
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