.TH MEMCACHED 1 "April 11, 2005"

.SH NAME

memcached \- high-performance memory object caching system

.SH SYNOPSIS

.B memcached

.RI [ options ]

.br

.SH DESCRIPTION

This manual page documents briefly the

.B memcached

memory object caching daemon.

.PP

.B 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.

.br

.SH OPTIONS

These programs follow the usual GNU command line syntax. A summary of options

is included below.

.TP

.B \-s, --unix-socket=<file>

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

.TP

.B \-A, --enable-shutdown

Enable ascii "shutdown" command.

.TP

.B \-a, --unix-mask=<perms>

Permissions (in octal format) for Unix socket created with \-s option.

.TP

.B \-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 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.

.TP

.B \-d, --daemon

Run memcached as a daemon.

.TP

.B \-u, --user=<username>

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

.TP

.B \-m, --memory-limit=<num>

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

.TP

.B \-c, --conn-limit=<num>

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

.TP

.B \-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.

.TP

.B \-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.

.TP

.B \-p, --port=<num>

Listen on TCP port <num>, the default is port 11211. 0 means off.

.TP

.B \-U, --udp-port=<num>

Listen on UDP port <num>, the default is port 0, which is off.

.TP

.B \-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.

.TP

.B \-r, --enable-coredumps

Raise the core file size limit to the maximum allowable.

.TP

.B \-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.

.TP

.B \-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.

.TP

.B \-C, --disable-cas

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

.TP

.B \-h, --help

Show the version of memcached and a summary of options.

.TP

.B \-v, --verbose

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

.TP

.B \-vv

Be even more verbose; same as \-v but also print client commands and

responses.

.TP

.B \-vvv

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

.TP

.B \-i, --license

Print memcached and libevent licenses.

.TP

.B \-P, --pidfile=<filename>

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

.TP

.B \-t, --threads=<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.

.TP

.B \-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.

.TP

.B \-L, --enable-largepages

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.

.TP

.B \-b, --listen-backlog=<num>

Set the backlog queue limit to <num> connections. The default is 1024.

.TP

.B \-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 options are "auto"

(the default, autonegotiation behavior), "ascii" and "binary".

.TP

.B \-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.

.TP

.B \-S, --enable-sasl

Turn on SASL authentication. This option is only meaningful if memcached was

compiled with SASL support enabled.

.TP

.B \-F, --disable-flush-all

Disables the "flush_all" command. The cmd_flush counter will increment, but

clients will receive an error message and the flush will not occur.

.TP

.B \-X, --disable-dumping

Disables the "stats cachedump" and "lru_crawler metadump" commands.

.TP

.B \-o, --extended=<options>

Comma separated list of extended or experimental options. See \-h or wiki for

up to date list.

.TP

.B \-V, --version

print version and exit

.br

.SH LICENSE

The memcached daemon is copyright Danga Interactive and is distributed under

the BSD license. Note that daemon clients are licensed separately.

.br

.SH SEE ALSO

The README file that comes with memcached

.br

.B https://www.memcached.org

.SH AUTHOR

The memcached daemon was written by Anatoly Vorobey

.B <mellon@pobox.com>

and Brad Fitzpatrick

.B <brad@danga.com>

and the rest of the crew of Danga Interactive

.B https://www.danga.com

.br