memcached

MEMCACHED(1)                General Commands Manual               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  alle-
       viate  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, --unix-socket=<file>
              Unix socket path to listen on (disables network support).

       -A, --enable-shutdown
              Enable ascii "shutdown" command.

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

       -l, --listen=<addr>
              Listen on <addr>; default to INADDR_ANY. <addr> may be specified
              as host:port.  If you don't specify a port number, the value you
              specified with -p or -U is used. You may  specify  multiple  ad-
              dresses  separated  by comma or by using -l multiple times. 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, --daemon
              Run memcached as a daemon.

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

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

       -c, --conn-limit=<num>
              Use <num> max simultaneous connections; the default is 1024.

       -R, --max-reqs-per-event=<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-memory
              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, --port=<num>
              Listen on TCP port <num>, the default is  port  11211.  0  means
              off.

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

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

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

       -f, --slab-growth-factor=<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, --slab-min-size=<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-cas
              Disable  the  use  of  CAS  (and  reduce  the per-item size by 8
              bytes).

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

       -v, --verbose
              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, --license
              Print memcached and libevent licenses.

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

       -t, --threads=<threads>
              Number of threads to use to process incoming requests. This  op-
              tion  is  only  meaningful if memcached was compiled with thread
              support enabled. 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, --enable-largepages
              Try  to  use  large  memory pages (if available). Increasing the
              memory page size could reduce the number of TLB misses  and  im-
              prove  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, --listen-backlog=<num>
              Set the backlog queue limit to <num> connections. The default is
              1024.

       -B, --protocol=<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  op-
              tions   are  "auto"  (the  default,  autonegotiation  behavior),
              "ascii" and "binary".

       -I, --max-item-size=<size>
              Override the default size of each slab page. The default size is
              1mb.  Default value for this parameter is 1m, minimum is 1k, max
              is 1G (1024 * 1024 * 1024).  Adjusting this  value  changes  the
              item size limit.

       -S, --enable-sasl
              Turn  on  SASL authentication. This option is only meaningful if
              memcached was compiled with SASL support enabled.

       -F, --disable-flush-all
              Disables the "flush_all" command. The cmd_flush counter will in-
              crement, but clients will receive an error message and the flush
              will not occur.

       -X, --disable-dumping
              Disables the "stats cachedump" and "lru_crawler  metadump"  com-
              mands.

       -o, --extended=<options>
              Comma separated list of extended or experimental options. See -h
              or wiki for up to date list.

       -V, --version
              print version and exit

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

SEE ALSO
       The README file that comes with memcached
       https://www.memcached.org

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

                                April 11, 2005                    MEMCACHED(1)