【Linux】tcp缓冲区大小的默认值、最大值
Author:阿冬哥
Created:2013-4-17
Blog:http://blog.csdn.net/c359719435/
Copyright 2013 阿冬哥 http://blog.csdn.net/c359719435/
使用以及转载请注明出处
case SO_SNDBUF:
/* Don't error on this BSD doesn't and if you think
about it this is right. Otherwise apps have to
play 'guess the biggest size' games. RCVBUF/SNDBUF
are treated in BSD as hints */ if (val > sysctl_wmem_max)//val是我们想设置的缓冲区大小的值
val = sysctl_wmem_max;//大于最大值,则val值设置成最大值 sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
if ((val * ) < SOCK_MIN_SNDBUF)//val的两倍小于最小值,则设置成最小值
sk->sk_sndbuf = SOCK_MIN_SNDBUF;
else
sk->sk_sndbuf = val * ;//val的两倍大于最小值,则设置成val值的两倍 /*
* Wake up sending tasks if we
* upped the value.
*/
sk->sk_write_space(sk);
break; case SO_RCVBUF:
/* Don't error on this BSD doesn't and if you think
about it this is right. Otherwise apps have to
play 'guess the biggest size' games. RCVBUF/SNDBUF
are treated in BSD as hints */ if (val > sysctl_rmem_max)
val = sysctl_rmem_max; sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
/* FIXME: is this lower bound the right one? */
if ((val * ) < SOCK_MIN_RCVBUF)
sk->sk_rcvbuf = SOCK_MIN_RCVBUF;
else
sk->sk_rcvbuf = val * ;
break;
SO_RCVBUF:
Sets or gets the maximum socket receive buffer in bytes.
The kernel doubles this value (to allow space for bookkeeping overhead) when it is set using setsockopt(),
and this doubled value is returned by getsockopt().
The default value is set by the /proc/sys/net/core/rmem_default file,
and the maximum allowed value is set by the /proc/sys/net/core/rmem_max file.
The minimum (doubled) value for this option is .
[root@cfs_netstorage core]# cat /proc/sys/net/core/rmem_default1048576[root@cfs_netstorage core]# cat /proc/sys/net/core/wmem_default512488
/proc/sys/net/ipv4/tcp_wmem[root@cfs_netstorage core]# cat /proc/sys/net/ipv4/tcp_wmem4096 16384 131072 //第一个表示最小值,第二个表示默认值,第三个表示最大值。/proc/sys/net/ipv4/tcp_rmem[root@cfs_netstorage core]# cat /proc/sys/net/ipv4/tcp_rmem4096 87380 174760
[root@ www.linuxidc.com]# cat /proc/sys/net/ipv4/tcp_rmem
4096 87380 4161536
87380 :tcp接收缓冲区的默认值
[root@ www.linuxidc.com]# cat /proc/sys/net/ipv4/tcp_wmem
4096 16384 4161536
16384 : tcp 发送缓冲区的默认值
2. tcp 或udp收发缓冲区最大值
[root@ www.linuxidc.com]# cat /proc/sys/net/core/rmem_max
131071
131071:tcp 或 udp 接收缓冲区最大可设置值的一半。
也就是说调用 setsockopt(s, SOL_SOCKET, SO_RCVBUF, &rcv_size, &optlen); 时rcv_size 如果超过 131071,那么
getsockopt(s, SOL_SOCKET, SO_RCVBUF, &rcv_size, &optlen); 去到的值就等于 131071 * 2 = 262142
[root@ www.linuxidc.com]# cat /proc/sys/net/core/wmem_max
131071
131071:tcp 或 udp 发送缓冲区最大可设置值得一半。
跟上面同一个道理
3. udp收发缓冲区默认值
[root@ www.linuxidc.com]# cat /proc/sys/net/core/rmem_default
111616:udp接收缓冲区的默认值
[root@ www.linuxidc.com]# cat /proc/sys/net/core/wmem_default
111616
111616:udp发送缓冲区的默认值
4. tcp 或udp收发缓冲区最小值
tcp 或udp接收缓冲区的最小值为 256 bytes,由内核的宏决定;
tcp 或udp发送缓冲区的最小值为 2048 bytes,由内核的宏决定
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