memcached(1)



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

       -A     Enable ascii "shutdown" command.

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

       -l <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
              addresses 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     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.

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

       -t <threads>
              Number  of  threads  to  use  to process incoming requests. This
              option 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     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 <num>
              Set the backlog queue limit to <num> connections. The default is
              1024.

       -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. The default size is
              1mb. Default value for this parameter 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.

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

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

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

       -V     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
       http://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 http://www.danga.com

                                April 11, 2005                    MEMCACHED(1)

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