Cached VS Buffers

最新推荐文章于 2024-03-25 17:35:11 发布

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最新推荐文章于 2024-03-25 17:35:11 发布

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分类专栏： Linux 文章标签： Linux Cached Buffers Kernel

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本文详细解释了Linux系统中/proc/meminfo文件内的Buffers和Cached的区别。Buffers指内存中的块I/O缓冲区大小，而Cached表示页面缓存的大小，不包括交换缓存部分。在现代Linux系统中，Cached是非常重要的指标，它能够达到几GB的大小，并且只有在内存压力增大时才会减小。

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What is the difference between Buffers and Cached columns in /proc/meminfo output?

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

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Robert Love, Used & developed Linux since its early days.

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.

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原文：http://www.quora.com/What-is-the-difference-between-Buffers-and-Cached-columns-in-proc-meminfo-output