1MEMCACHED(1) General Commands Manual MEMCACHED(1)
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6 memcached - high-performance memory object caching system
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9 memcached [options]
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12 This manual page documents briefly the memcached memory object caching
13 daemon.
14 memcached is a flexible memory object caching daemon designed to alle‐
16 viate database load in dynamic web applications by storing objects in
17 memory. It's based on libevent to scale to any size needed, and is
18 specifically optimized to avoid swapping and always use non-blocking
19 I/O.
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22 These programs follow the usual GNU command line syntax. A summary of
23 options is included below.
24 -s <file>
26 Unix socket path to listen on (disables network support).
27 -a <perms>
29 Permissions (in octal format) for Unix socket created with -s
30 option.
31 -l <ip_addr>
33 Listen on <ip_addr>; default to INADDR_ANY. This is an important
34 option to consider as there is no other way to secure the
35 installation. Binding to an internal or firewalled network
36 interface is suggested.
37 -d Run memcached as a daemon.
39 -u <username>
41 Assume the identity of <username> (only when run as root).
42 -m <num>
44 Use <num> MB memory max to use for object storage; the default
45 is 64 megabytes.
46 -c <num>
48 Use <num> max simultaneous connections; the default is 1024.
49 -R <num>
51 This option seeks to prevent client starvation by setting a
52 limit to the number of sequential requests the server will
53 process from an individual client connection. Once a connection
54 has exceeded this value, the server will attempt to process I/O
55 on other connections before handling any further request from
56 this connection. The default value for this option is 20.
57 -k Lock down all paged memory. This is a somewhat dangerous option
59 with large caches, so consult the README and memcached homepage
60 for configuration suggestions.
61 -p <num>
63 Listen on TCP port <num>, the default is port 11211.
64 -U <num>
66 Listen on UDP port <num>, the default is port 11211, 0 is off.
67 -M Disable automatic removal of items from the cache when out of
69 memory. Additions will not be possible until adequate space is
70 freed up.
71 -r Raise the core file size limit to the maximum allowable.
73 -f <factor>
75 Use <factor> as the multiplier for computing the sizes of memory
76 chunks that items are stored in. A lower value may result in
77 less wasted memory depending on the total amount of memory
78 available and the distribution of item sizes. The default is
79 1.25.
80 -n <size>
82 Allocate a minimum of <size> bytes for the item key, value, and
83 flags. The default is 48. If you have a lot of small keys and
84 values, you can get a significant memory efficiency gain with a
85 lower value. If you use a high chunk growth factor (-f option),
86 on the other hand, you may want to increase the size to allow a
87 bigger percentage of your items to fit in the most densely
88 packed (smallest) chunks.
89 -C Disable the use of CAS (and reduce the per-item size by 8
91 bytes).
92 -h Show the version of memcached and a summary of options.
94 -v Be verbose during the event loop; print out errors and warnings.
96 -vv Be even more verbose; same as -v but also print client commands
98 and responses.
99 -i Print memcached and libevent licenses.
101 -P <filename>
103 Print pidfile to <filename>, only used under -d option.
104 -t <threads>
106 Number of threads to use to process incoming requests. This
107 option is only meaningful if memcached was compiled with thread
108 support enabled. It is typically not useful to set this higher
109 than the number of CPU cores on the memcached server. The
110 default is 4.
111 -D <char>
113 Use <char> as the delimiter between key prefixes and IDs. This
114 is used for per-prefix stats reporting. The default is ":"
115 (colon). If this option is specified, stats collection is turned
116 on automatically; if not, then it may be turned on by sending
117 the "stats detail on" command to the server.
118 -L Try to use large memory pages (if available). Increasing the
120 memory page size could reduce the number of TLB misses and
121 improve the performance. In order to get large pages from the
122 OS, memcached will allocate the total item-cache in one large
123 chunk. Only available if supported on your OS.
124 -B <proto>
126 Specify the binding protocol to use. By default, the server
127 will autonegotiate client connections. By using this option,
128 you can specify the protocol clients must speak. Possible
129 options are "auto" (the default, autonegotiation behavior),
130 "ascii" and "binary".
131 -I <size>
133 Override the default size of each slab page. Default is 1mb.
134 Default is 1m, minimum is 1k, max is 128m. Adjusting this value
135 changes the item size limit. Beware that this also increases
136 the number of slabs (use -v to view), and the overal memory
137 usage of memcached.
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140 The memcached daemon is copyright Danga Interactive and is distributed
141 under the BSD license. Note that daemon clients are licensed sepa‐
142 rately.
143
145 The README file that comes with memcached
146 http://www.danga.com/memcached
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149 The memcached daemon was written by Anatoly Vorobey <mellon@pobox.com>
150 and Brad Fitzpatrick <brad@danga.com> and the rest of the crew of Danga
151 Interactive http://www.danga.com
152 April 11, 2005 MEMCACHED(1)