Technical data

Tuning Techniques
2.1 Subsystem Attributes
2.1.5.3 Increasing the Maximum Size of a Socket Buffer
The socket subsystem attribute sb_max specifies the maximum size of a socket
buffer.
Performance Benefits and Tradeoffs
Increasing the maximum size of a socket buffer may improve performance if your
applications can benefit from a large buffer size.
You can modify the sb_max attribute without rebooting the system.
When to Tune
If you require a large socket buffer, increase the maximum socket buffer size.
Recommended Values
The default value of the
sb_max attribute is 128 KB. Increase this value before
you increase the size of the transmit and receive socket buffers.
2.1.6 Modifying Internet Subsystem Attributes
You may be able to improve inet subsystem performance by modifying the
attributes described in Table 2–3.
Table 2–3 inet Subsystem Attributes
Attribute Description
tcbhashsize Controls the size of a TCP hash table.
tcbhashnum Specifies the number of TCP hash tables.
inifaddr_hsize Controls the size of the kernel interface alias table.
tcp_keepinit Specifies the TCP partial connection timeout rate.
tcp_rexmit_interval_min Specifies the rate of TCP retransmissions.
tcp_keepalive_default Enables or disables the TCP keepalive function.
tcp_msl Specifies the TCP connection context timeout rate.
tcp_nodelack
Delays acknowledgment messages after the receipt of
network frames.
ipport_userreserved Specifies the maximum value for the range of outgoing
connection ports.
ipport_userreserved_min Specifies the minimum value for the range of outgoing
connection ports.
pmtu_enabled Enables or disables use of the PMTU protocol.
ipqmaxlen Prevents dropped input packets.
2.1.6.1 Increasing the Size of a TCP Hash Table
You can modify the size of the hash table that the kernel uses to look up
Transmission Control Protocol (TCP) control blocks. The inet subsystem
attribute tcbhashsize specifies the number of hash buckets in the kernel TCP
connection table (the number of buckets in the
inpcb hash table).
Performance Benefits and Tradeoffs
The kernel must look up the connection block for every TCP packet it receives, so
increasing the size of the table can speed the search and improve performance.
This results in a small increase in pooled memory.
You can modify the tcbhashsize attribute without rebooting the system.
Tuning Techniques 2–9