overcommit的策略通过vm.overcommit_memory设置。
overcommit的百分比由vm.overcommit_ratio设置。
当oom-killer发生时，linux会选择杀死哪些进程选择进程的函数是oom_badness函数(在mm/oom_kill.c中)，该函数会计算每个进程的点数(0~1000)。点数越高，这个进程越有可能被杀死。每个进程的点数跟oom_score_adj有关，而且oom_score_adj可以被设置(-1000最低，1000最高)。
设置Redis外网可访问值得注意的是在3.2.0以后的新版本中引入了一种proteced mode 模式，详见：
在不修改配置文件任何内容的情况下，有以下几个默认的配置：
# By default, if no "bind" configuration directive is specified, Redis listens # for connections from all the network interfaces available on the server. # It is possible to listen to just one or multiple selected interfaces using # the "bind" configuration directive, followed by one or more IP addresses. # # Examples: # # bind 192.168.1.100 10.0.0.1 # bind 127.0.0.1 ::1 # # ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the # internet, binding to all the interfaces is dangerous and will expose the # instance to everybody on the internet. So by default we uncomment the # following bind directive, that will force Redis to listen only into # the IPv4 lookback interface address (this means Redis will be able to # accept connections only from clients running into the same computer it # is running). # # IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES # JUST COMMENT THE FOLLOWING LINE. # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ bind 127.0.0.1 # By default protected mode is enabled. You should disable it only if # you are sure you want clients from other hosts to connect to Redis # even if no authentication is configured, nor a specific set of interfaces # are explicitly listed using the "bind" directive. protected-mode yes # Require clients to issue AUTH <PASSWORD> before processing any other # commands. This might be useful in environments in which you do not trust # others with access to the host running redis-server. # # This should stay commented out for backward compatibility and because most # people do not need auth (e.g. they run their own servers). # # Warning: since Redis is pretty fast an outside user can try up to # 150k passwords per second against a good box. This means that you should # use a very strong password otherwise it will be very easy to break. # # requirepass foobared简单的就是：
bind 127.0.0.1 protected-mode yes # requirepass foobared默认绑定的是127.0.01，默认开启了：protected-mode模式，按照官方的说法，如果默认开启了protected-mode模式在没有配置绑定IP和密码的情况下，是只允许回环地址进行访问的，就只允许127.0.0.1进行访问，那我们就在默认的配置下进行启动，通过SSH工具在其他机器上进行访问，看看运行的效果：
[root@localhost redis-3.2.1]# ./src/redis-server ../redis.conf
很显然是没有办法访问到，在3.2.0以前的版本中可以将绑定的IP进行修改为本机IP，例如我运行Redis的服务器IP为192.168.1.149，那我的配置为0.0.0.0，顺便指定Redis的密码，# requirepass foobared 将这一行去掉注释，选择自己喜欢的密码，重启服务即可正常访问。
DENIED Redis is running in protected mode because protected mode is enabled