Deciding whether to get a buffer cache block or inode block Post: 302565252

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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

10-17-2011

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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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kswitch

KSWITCH(1)						      General Commands Manual							KSWITCH(1)

NAME

       kswitch - switch primary credential cache

SYNOPSIS

       kswitch {-c cachename | -p principal}

DESCRIPTION

       kswitch makes the specified credential cache the primary cache for the collection, if a cache collection is available.

OPTIONS

       -c     cachename directly specifies the credential cache to be made primary.

       -p     principal  causes  the cache collection to be searched for a cache containing credentials for principal.	If one is found, that col-
	      lection is made primary.

ENVIRONMENT

       kswitch uses the following environment variables:

       KRB5CCNAME      Location of the default Kerberos 5 credentials (ticket) cache, in the form type:residual.  If no type  prefix  is  present,
		       the  FILE  type	is  assumed.   The  type  of  the  default cache may determine the availability of a cache collection; for
		       instance, a default cache of type DIR causes caches within the directory to be present in the collection.

FILES

       /tmp/krb5cc_[uid]  default location of Kerberos 5 credentials cache ([uid] is the decimal UID of the user).

SEE ALSO

       kinit(1), kdestroy(1), klist(1), kerberos(1)

																	KSWITCH(1)