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       /etc/cachefilesd.conf - Local file caching configuration file


       The  configuration  file  for cachefilesd which can manage a persistent
       cache for a variety of network filesystems using a set of files  on  an
       already mounted filesystem as the data store.


       This  configuration  file  can  contain a number of commands.  Each one
       should be on a separate line.  Blank lines and lines beginning  with  a
       ’#’ character are considered to be comments and are discarded.

       The only mandatory command is:

       dir <path>
              This  command specifies the directory containing the root of the
              cache.  It may only specified once per configuration file.

       All the other commands are optional:

       brun <N>%

       bcull <N>%

       bstop <N>%

       frun <N>%

       fcull <N>%

       fstop <N>%
              These commands configure the culling limits.  The  defaults  are
              7% (run), 5% (cull) and 1% (stop) respectively.  See the section
              on cache culling for more information.

              The commands beginning with a ’b’ are file space (block) limits,
              those beginning with an ’f’ are file count limits.

       tag <name>
              This   command   specifies   a   tag   to  FS-Cache  to  use  in
              distinguishing multiple caches.  This is only required  if  more
              than   one   cache   is  going  to  be  used.   The  default  is

       culltable <log2size>
              This command specifies the size of the tables holding the  lists
              of  cullable  objects  in the cache.  The bigger the number, the
              faster and more smoothly that culling can proceed when there are
              many  objects in the cache, but the more memory will be consumed
              by cachefilesd.

              The quantity is specified as log2 of the size actually required,
              for  example  12  indicates  a  table  of  4096  entries  and 13
              indicates 8192 entries.  The permissible values are  between  12
              and  20,  the latter indicating 1048576 entries.  The default is

       debug <mask>
              This command specifies a numeric bitmask to control debugging in
              the  kernel  module.   The  default  is  zero  (all  off).   The
              following values can be OR’d into the mask  to  collect  various

              1      Turn on trace of function entry (_enter() macros)

              2      Turn on trace of function exit (_leave() macros)

              4      Turn on trace of internal debug points (_debug())

              This       mask      can      also      be      set      through


       As an example, consider the following:

              dir /var/fscache
              tag mycache
              brun 10%
              bcull 7%
              bstop 3%

       The  places  the  cache  storage  objects   in   a   directory   called
       "/var/fscache",  names  the  cache  "mycache", permits the cache to run
       freely as long as there’s at least 10%  free  space  on  /var/fscache/,
       starts  culling  the cache when the free space drops below 7% and stops
       writing new stuff into the cache if the  amount  of  free  space  drops
       below  3%.   If  the  cache is suspended, it won’t reactivate until the
       amount of free space rises again to 10% or better.


       The cache may need culling occasionally to make space.   This  involves
       discarding  objects  from  the  cache that have been used less recently
       than anything else.  Culling is  based  on  the  access  time  of  data
       objects.  Empty directories are culled if not in use.

       Cache  culling is done on the basis of the percentage of blocks and the
       percentage of files available in the underlying filesystem.  There  are
       six "limits":


       frun   If the amount of free space and the number of available files in
              the cache rises above both these limits, then culling is  turned


       fcull  If  the  amount  of  available  space or the number of available
              files in the cache falls below  either  of  these  limits,  then
              culling is started.


       fstop  If  the  amount  of  available  space or the number of available
              files in the cache falls below either of these limits,  then  no
              further  allocation  of  disk  space or files is permitted until
              culling has raised things above these limits again.

       These must be configured thusly:

              0 <= bstop < bcull < brun < 100
              0 <= fstop < fcull < frun < 100

       Note that these are percentages of available space and available files,
       and  do  not  appear  as  100  minus the percentage displayed by the df

       The userspace daemon scans the cache to build up a  table  of  cullable
       objects.   These  are  then culled in least recently used order.  A new
       scan of the cache is started as soon as space is  made  in  the  table.
       Objects  will  be skipped if their atimes have changed or if the kernel
       module says it is still using them.


       cachefilesd(8), df(1), /usr/share/doc/cachefilesd-*/README


       The cachefilesd software has been developed by David Howells