In <[🔎] 4D58173B.7050005@gmail.com>, George Shuklin wrote: >What data stored in Buffers area, and what data a stored in Cached area? >And what difference between them? > >If you know at least one article in kernels sources/Documentation >folder, or anywhere in Internet, I'll read it gladly. http://www.linuxhowtos.org/System/Linux%20Memory%20Management.htm First hit when doing this search, here: http://www.google.com/search?q=what+is+the+difference+between+buffers+and+cache+in+linux+kernel+memory+reports&ie=UTF-8&oe=UTF-8 It has a section called "The difference between buffers and cache". So, searching the web is a good start but, I can't say I know that there is specific documentation about this. My understanding is: "cache" is RAM that exactly mirrors a part of the block device, or at least a whole page in size. "cache" is used for satisfying read requests to that part of the block device, instead of doing real I/O. When a write occurs that that part of the disk the cache is invalidated and the RAM is scheduled for reuse. "cache" can be dropped at any time with just a performance hit. "buffers" can be any size (not necessarily a multiple of the page size) and are used mainly for write operations. Instead of waiting for I/O to finish before returning from a system call, data is stored in a "buffer". Once the "buffer" is confirmed as written to disk, the RAM is scheduled for reuse. "buffers" can't be dropped until their I/O completes. It seems that buffers can turn into cache and vice-versa for certain use cases, but I don't know if the kernel actually does that. Both types of memory are effectively free. Cache can be dropped willy-nilly. Buffers can be reclaimed by waiting for their I/O to complete. Both of these actions are done automatically by the kernel when application memory pressure increases. -- Boyd Stephen Smith Jr. ,= ,-_-. =. bss@iguanasuicide.net ((_/)o o(\_)) ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-' http://iguanasuicide.net/ \_/
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