Sun Microsystems 820434310 manual Sizing the Connection Hash Table, Ndd -get /dev/tcp tcpconnhash

Tuning for the Solaris OS

TABLE 5–1Tuning Parameters for Solaris		(Continued)
Parameter	Scope		Default	Tuned Value	Comments
tcp_conn_req_max_q	ndd /dev/tcp		128	1024
tcp_conn_req_max_q0	ndd /dev/tcp		1024	4096
tcp_ip_abort_interval	ndd /dev/tcp		480000	60000
tcp_keepalive_interval	ndd /dev/tcp		7200000	900000	For high traffic web sites, lower this
					value.
tcp_rexmit_interval_initial	ndd /dev/tcp		3000	3000	If retransmission is greater than
					30-40%, you should increase this
					value.
tcp_rexmit_interval_max	ndd /dev/tcp		240000	10000
tcp_rexmit_interval_min	ndd /dev/tcp		200	3000
tcp_smallest_anon_port	ndd /dev/tcp		32768	1024	Set on clients too.
tcp_slow_start_initial	ndd /dev/tcp		1	2	Slightly faster transmission of small
					amounts of data.
tcp_xmit_hiwat	ndd /dev/tcp		8129	32768	Size of transmit buffer.
tcp_recv_hiwat	ndd /dev/tcp		8129	32768	Size of receive buffer.
tcp_conn_hash_size	ndd /dev/tcp		512	8192	Size of connection hash table. See
					“Sizing the Connection Hash Table”
					on page 96.

Sizing the Connection Hash Table

The connection hash table keeps all the information for active TCP connections. Use the following command to get the size of the connection hash table:

ndd -get /dev/tcp tcp_conn_hash

This value does not limit the number of connections, but it can cause connection hashing to take longer. The default size is 512.

To make lookups more efficient, set the value to half of the number of concurrent TCP connections that are expected on the server. You can set this value only in /etc/system, and it becomes effective at boot time.

Use the following command to get the current number of TCP connections.

netstat -nP tcpwc -l

96 Sun GlassFish Enterprise Server 2.1 Performance Tuning Guide • January 2009