redis动态增加内存(不重启)

在redis的使用过程中，有时候需要修改redis的配置，如在业务运行的情况下，内存不够怎么办，这时要么赶紧删除无用的内存，要么扩展内存。如果有无用的内容可删除那么所有问题都已经解决。如果内容都是重要的，那只能选择扩展内存。说到扩展内存，redis为我们提供了一个动态调整的命令。
CONFIG SET （官网https://redis.io/commands/config-set）
CONFIG SET parameter value
CONFIG SET 命令可以动态地调整 Redis 服务器的配置(configuration)而无须重启。
你可以使用它修改配置参数，或者改变 Redis 的持久化(Persistence)方式。
CONFIG SET 可以修改的配置参数可以使用命令 CONFIG GET * 来列出，所有被 CONFIG SET 修改的配置参数都会立即生效。
关于 CONFIG SET 命令的更多消息，请参见命令 CONFIG GET 的说明。
关于如何使用 CONFIG SET 命令修改 Redis 持久化方式，请参见 Redis Persistence 。

可用版本：
>= 2.0.0
时间复杂度：
不明确
返回值：
当设置成功时返回 OK ，否则返回一个错误。

例：动态添加内存 3G到10G
1、获取当前值
redis 127.0.0.1:6379> config get maxmemory

1. "maxmemory"
2. "3221225472"

2、设置新数值
redis 127.0.0.1:6379> config set maxmemory 10737418240
OK

3、查看修改后的值
redis 127.0.0.1:6379> CONFIG GET maxmemory

1. "maxmemory"
2. "10737418240"

我们看看那些参数 redis可以动态设置
127.0.0.1:6379> CONFIG GET *

1. "dbfilename"
2. "dump.rdb"
3. "requirepass"
4. "123456"
5. "masterauth"
6. ""
7. "unixsocket"
8. ""
9. "logfile"
10. "/diskc/redis-2.8.19/log/6379_slave.log"
11. "pidfile"
12. "/var/run/redis.pid"
13. "maxmemory"
14. "10737418240"
15. "maxmemory-samples"
16. "3"
17. "timeout"
18. "0"
19. "tcp-keepalive"
20. "0"
21. "auto-aof-rewrite-percentage"
22. "100"
23. "auto-aof-rewrite-min-size"
24. "67108864"
25. "hash-max-ziplist-entries"
26. "512"
27. "hash-max-ziplist-value"
28. "64"
29. "list-max-ziplist-entries"
30. "512"
31. "list-max-ziplist-value"
32. "64"
33. "set-max-intset-entries"
34. "512"
35. "zset-max-ziplist-entries"
36. "128"
37. "zset-max-ziplist-value"
38. "64"
39. "hll-sparse-max-bytes"
40. "3000"
41. "lua-time-limit"
42. "5000"
43. "slowlog-log-slower-than"
44. "100000"
45. "latency-monitor-threshold"
46. "0"
47. "slowlog-max-len"
48. "128"
49. "port"
50. "6379"
51. "tcp-backlog"
52. "511"
53. "databases"
54. "16"
55. "repl-ping-slave-period"
56. "10"
57. "repl-timeout"
58. "60"
59. "repl-backlog-size"
60. "1048576"
61. "repl-backlog-ttl"
62. "3600"
63. "maxclients"
64. "15000"
65. "watchdog-period"
66. "200"
67. "slave-priority"
68. "100"
69. "min-slaves-to-write"
70. "0"
71. "min-slaves-max-lag"
72. "10"
73. "hz"
74. "10"
75. "repl-diskless-sync-delay"
76. "5"
77. "no-appendfsync-on-rewrite"
78. "no"
79. "slave-serve-stale-data"
80. "yes"
81. "slave-read-only"
82. "yes"
83. "stop-writes-on-bgsave-error"
84. "yes"
85. "daemonize"
86. "yes"
87. "rdbcompression"
88. "yes"
89. "rdbchecksum"
90. "yes"
91. "activerehashing"
92. "yes"
93. "repl-disable-tcp-nodelay"
94. "no"
95. "repl-diskless-sync"
96. "no"
97. "aof-rewrite-incremental-fsync"
98. "yes"
99. "aof-load-truncated"
100. "yes"
101. "appendonly"
102. "no"
103. "dir"
104. "/diskc/redis-2.8.19"
105. "maxmemory-policy"
106. "volatile-lru"
107. "appendfsync"
108. "everysec"
109. "save"
110. "900 1 300 10 60 10000"
111. "loglevel"
112. "notice"
113. "client-output-buffer-limit"
114. "normal 0 0 0 slave 268435456 67108864 60 pubsub 33554432 8388608 60"
115. "unixsocketperm"
116. "0"
117. "slaveof"
118. ""
119. "notify-keyspace-events"
120. ""
121. "bind"
122. ""