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Linux 2.6 - man page for memcached (linux section 1)

MEMCACHED(1)									     MEMCACHED(1)

NAME
       memcached - high-performance memory object caching system

SYNOPSIS
       memcached [options]

DESCRIPTION
       This manual page documents briefly the memcached memory object caching daemon.

       memcached  is  a flexible memory object caching daemon designed to alleviate database load
       in dynamic web applications by storing objects in memory.  It's based on libevent to scale
       to  any	size  needed, and is specifically optimized to avoid swapping and always use non-
       blocking I/O.

OPTIONS
       These programs follow the usual GNU command line syntax. A summary of options is  included
       below.

       -s <file>
	      Unix socket path to listen on (disables network support).

       -a <perms>
	      Permissions (in octal format) for Unix socket created with -s option.

       -l <ip_addr>
	      Listen on <ip_addr>; default to INADDR_ANY. This is an important option to consider
	      as there is no other way to secure the installation.  Binding  to  an  internal  or
	      firewalled network interface is suggested.

       -d     Run memcached as a daemon.

       -u <username>
	      Assume the identity of <username> (only when run as root).

       -m <num>
	      Use <num> MB memory max to use for object storage; the default is 64 megabytes.

       -c <num>
	      Use <num> max simultaneous connections; the default is 1024.

       -R <num>
	      This  option seeks to prevent client starvation by setting a limit to the number of
	      sequential requests the server will process from an individual  client  connection.
	      Once  a  connection has exceeded this value, the server will attempt to process I/O
	      on other connections before handling any further request from this connection.  The
	      default value for this option is 20.

       -k     Lock  down all paged memory. This is a somewhat dangerous option with large caches,
	      so consult the README and memcached homepage for configuration suggestions.

       -p <num>
	      Listen on TCP port <num>, the default is port 11211.

       -U <num>
	      Listen on UDP port <num>, the default is port 11211, 0 is off.

       -M     Disable automatic removal of items from the cache when out  of  memory.	Additions
	      will not be possible until adequate space is freed up.

       -r     Raise the core file size limit to the maximum allowable.

       -f <factor>
	      Use  <factor> as the multiplier for computing the sizes of memory chunks that items
	      are stored in. A lower value may result in less  wasted  memory  depending  on  the
	      total  amount  of memory available and the distribution of item sizes.  The default
	      is 1.25.

       -n <size>
	      Allocate a minimum of <size> bytes for the item key, value, and flags. The  default
	      is 48. If you have a lot of small keys and values, you can get a significant memory
	      efficiency gain with a lower value. If you use  a  high  chunk  growth  factor  (-f
	      option),	on  the  other	hand, you may want to increase the size to allow a bigger
	      percentage of your items to fit in the most densely packed (smallest) chunks.

       -C     Disable the use of CAS (and reduce the per-item size by 8 bytes).

       -h     Show the version of memcached and a summary of options.

       -v     Be verbose during the event loop; print out errors and warnings.

       -vv    Be even more verbose; same as -v but also print client commands and responses.

       -vvv   Be extremely verbose; same of the above and also print internal state transitions.

       -i     Print memcached and libevent licenses.

       -I     Override the size of each slab page in bytes. In mundane words, it adjusts the max-
	      imum  item  size	that  memcached will accept.  You can use the suffixes K and M to
	      specify the size as well, so use 2000000 or 2000K or 2M if you want a maximum  size
	      of  2 MB per object.  It is not recommended to raise this limit above 1 MB due just
	      to performance reasons.  The default value is 1 MB.

       -P <filename>
	      Print pidfile to <filename>, only used under -d option.

       -t <threads>
	      Number of threads to use to process incoming requests.  It is typically not  useful
	      to set this higher than the number of CPU cores on the memcached server.	Setting a
	      high number (64 or more) of worker threads is not recommended.  The default is 4.

       -D <char>
	      Use <char> as the delimiter between key prefixes and IDs.  This is  used	for  per-
	      prefix  stats reporting.	The default is ":" (colon).  If this option is specified,
	      stats collection is turned on automatically; if not, then it may be  turned  on  by
	      sending the "stats detail on" command to the server.

       -L     Try  to  use  large  memory  pages (if available).  Increasing the memory page size
	      could reduce the number of TLB misses and improve the performance.  In order to get
	      large  pages from the OS, memcached will allocate the total item-cache in one large
	      chunk.  Only available if supported on your OS.

       -B <proto>
	      Specify the binding protocol to use.  By default,  the  server  will  autonegotiate
	      client  connections.   By  using	this option, you can specify the protocol clients
	      must speak.  Possible options are "auto" (the default,  autonegotiation  behavior),
	      "ascii" and "binary".

       -I <size>
	      Override the default size of each slab page. Default is 1mb. Default is 1m, minimum
	      is 1k, max is 128m. Adjusting this value changes the item size limit.  Beware  that
	      this  also  increases  the  number of slabs (use -v to view), and the overal memory
	      usage of memcached.

LICENSE
       The memcached daemon is copyright Danga Interactive  and  is  distributed  under  the  BSD
       license. Note that daemon clients are licensed separately.

SEE ALSO
       The README file that comes with memcached
       http://www.danga.com/memcached

AUTHOR
       The  memcached  daemon  was  written  by Anatoly Vorobey <mellon@pobox.com> and Brad Fitz-
       patrick	 <brad@danga.com>   and   the	rest   of   the   crew	 of   Danga   Interactive
       http://www.danga.com

					 October 16, 2009			     MEMCACHED(1)


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