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Top Forums UNIX for Advanced & Expert Users Deciding whether to get a buffer cache block or inode block Post 302565252 by Corona688 on Monday 17th of October 2011 11:29:02 AM
Old 10-17-2011
Cache is not technically needed. It's not like a file handle, where you must have one to do anything. It's just a copy of data held in memory in case you need to read it again, which makes future accesses much faster.

Caches are a kernel thing, not a process thing. The kernel decides what things should be cached, not the process, and the caches reside in the kernel, not the process. Usually, caches are a fairly ephemeral thing. If you need to allocate more memory and the memory's full of cache, piff, the kernel throws some Not Recently Used cache away and gives you the memory.

"buffer" is a vague term. I presume it's talking about file buffers?

Inode caches cache inodes, file buffers cache file contents. To stat() a file you are reading its inode, when you read() from a file you are getting its contents.
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CACHEINFO(5)							AFS File Reference						      CACHEINFO(5)

NAME
cacheinfo - Defines configuration parameters for the Cache Manager DESCRIPTION
The cacheinfo file defines configuration parameters for the Cache Manager, which reads the file as it initializes. The file contains a single line of ASCII text and must reside in the /etc/openafs directory. Use a text editor to create it during initial configuration of the client machine; the required format is as follows: <mount>:<cache>:<size> where <mount> Names the local disk directory at which the Cache Manager mounts the AFS namespace. It must exist before the afsd program runs. The conventional value is /afs. Using any other value prevents traversal of pathnames that begin with /afs (such as pathnames to files in foreign cells that do use the conventional name). The -mountdir argument to the afsd command overrides this value. <cache> Names the local disk directory to use as a cache. It must exist before the afsd program runs. The standard value is /usr/vice/cache, but it is acceptable to substitute a directory on a partition with more available space. Although the Cache Manager ignores this field when configuring a memory cache, a value must always appear in it. The -cachedir argument to the afsd command overrides this value. <size> Specifies the cache size as a number of 1-kilobyte blocks. Larger caches generally yield better performance, but a disk cache must not exceed 90% of the space available on the cache partition (85% for AIX systems), and a memory cache must use no more than 25% of available machine memory. The -blocks argument to the afsd command overrides this value. To reset cache size without rebooting on a machine that uses disk caching, use the fs setcachesize command. To display the current size of a disk or memory cache between reboots, use the fs getcacheparms command. EXAMPLES
The following example cacheinfo file mounts the AFS namespace at /afs, establishes a disk cache in the /usr/vice/cache directory, and defines cache size as 50,000 1-kilobyte blocks. /afs:/usr/vice/cache:50000 SEE ALSO
afsd(8), fs_getcacheparms(1), fs_setcachesize(1) COPYRIGHT
IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved. This documentation is covered by the IBM Public License Version 1.0. It was converted from HTML to POD by software written by Chas Williams and Russ Allbery, based on work by Alf Wachsmann and Elizabeth Cassell. OpenAFS 2012-03-26 CACHEINFO(5)
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