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Tune SIP servlets for Linux

 

This page describes preliminary SIP servlet tuning for Linux 2.6 kernel. A Session Initiation Protocol (SIP) servlet under load might retransmit messages or drop calls. The UDP socket queues might fill. A review of the verbose garbage collection output might show that there are fairly long garbage collection times, for example, 0.5 to 1.5 seconds. The cause of this problem is that the Ethernet driver, Linux® operating system, WebSphere® Application Server, or any combination of the items are not tuned for SIP applications. You can apply the following levels of tuning.

The following recommendations have been tested on Red Hat Enterprise Linux 4 only and are provided as is without any implied warranty.

 

Overview

Linux Ethernet driver

Linux Ethernet driver tuning begins by selecting the best Ethernet driver. For example, the HS20 blades recommended driver is the tg3-3.43b driver (or later), which can be found at the Web site for Broadcom Ethernet NIC Driver Downloads. The following shell commands have been used to tune the Linux kernel Ethernet driver: 

/sbin/ifconfig eth0 txqueuelen 2000
/sbin/ifconfig eth2 txqueuelen 2000 ethtool -s eth0 autoneg off speed 1000 duplex full ethtool -A eth0 autoneg off rx on tx on ethtool -C eth0 adaptive-rx off adaptive-tx off rx- usecs 20 rx-frames 5 tx-usecs 60 tx-frames 11 ethtool -G eth0 rx 511 rx-jumbo 255 tx 511
Depending upon the Ethernet driver that is installed, some of these options might need to change.

Linux kernel

Linux kernel tuning uses the following commands: 

echo 1048576 > /proc/sys/net/core/rmem_max echo 1048576 > /proc/sys/net/core/rmem_default echo 1048576 > /proc/sys/net/core/wmem_max echo 1048576 > /proc/sys/net/core/wmem_default echo 10000000 > /proc/sys/net/core/optmem_max echo 262143 262143 262143 > /proc/sys/net/ipv4/tcp_rmem echo 262143 262143 262143 > /proc/sys/net/ipv4/tcp_wmem echo 8388608 8388608 8388608 > /proc/sys/net/ipv4/tcp_mem echo 400 > /proc/sys/net/unix/max_dgram_qlen echo 400 > /proc/sys/net/core/message_burst echo 2800 > /proc/sys/net/core/mod_cong echo 1000 > /proc/sys/net/core/lo_cong echo 200 > /proc/sys/net/core/no_cong echo 2900 > /proc/sys/net/core/no_cong_thresh echo 3000 > /proc/sys/net/core/netdev_max_backlog
This configuration might not be optimum for a given application and you might need to adjust the configuration to achieve the best performance. However, you might use these values as a starting point.

SIP for WebSphere Application Server SIP tuning for WAS is completed using the following steps:

  1. Create a separate thread pool for the SIP servlet container. Follow this path in the console:

    1. Click Server > Application servers > server_name .

    2. Under Additional properties, click Thread Pools > New.

    3. In the Name field, enter SipContainer.

    4. In the Minimum Size and Maximum Size fields, enter 15. These values should be adequate for most applications.

    5. Click OK.

  2. Create custom properties for the SIP Servlet container. Follow this path in the console:

    1. Click Server > Application servers > server_name .

    2. Click SIP container.

    3. Under Additional properties, click Custom Properties > New.

    4. In the Name field, enter javax.sip.max.object.pool.size.

    5. In the Value field, enter 1000.

    6. Click OK.

    7. In the Name field, enter max.tu.pool.size.

    8. In the Value field, enter 1000.

    9. Click OK.

  3. Create custom properties for the SIPUDP channel if User Datagram Protocol (UDP) is the primary transport for SIP traffic. Follow this path in the administrative console:

    1. Click Server > Application servers > server_name .

    2. Click SIP container > Transport Chain > SIPCInboundDefaultUDP > UDP Inbound channel (UDP1).

    3. Under Additonal Properties, click Custom Properties > New.

    4. In the Name field, enter receiveBufferSocketSize.

    5. In the Value field, enter 3000000.

    6. Click OK.

    7. In the Name field, enter sendBufferSocketSize.

    8. In the Value field, enter 3000000.

  4. Specify the SIP servlet container general properties. Follow this path in the console:

    1. Click Servers > Application Servers > server_name > SIP container.

    2. Enter the Maximum application sessions value. The Maximum application sessions value can be calculated as: Maximum call hold time or session timeout x Call rate x Safety factor.

    3. Enter the Maximum messages per averaging period value. The Maximum messages per averaging period value can be calculated as: Maximum call hold time or session timeout x Maximum rate of SIP messages x Safety factor.

    4. Enter the Maximum dispatch queue size value. The Maximum dispatch queue size value can be calculated as: Maximum rate of SIP messages x Maximum latency in SIP processing x Safety factor.

    5. Set the thread pool to the newly created SIP container thread pool (to the drop down name "SipContainer").

  5. Tune the JVM garbage collection policy. Follow this path in the console:

    1. Click Server > Application servers > server_name .

    2. Under Server Infrastructure, click Java and Process Management > Process Definition.

    3. Under Additional Properties, click Java Virtual Machine.

    4. In the Generic JVM arguments field, enter the following value as one continuous line: 1"-Xgcpolicy:gencon -Xgc:scvNoAdaptiveTenure,scvTenureAge=8, stdGlobalCompactToSatisfyAllocate".

Optional: You also might add a value of 768 to the Initial Heap Size and Maximum Heap Size fields. It is also a good practice to enable the Verbose garbage collection option during performance testing or tuning operations.


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