Determining IPC Requirements

4.10 Determining IPC Requirements

The values of different system parameters determine IPC requirements. You can use the tmboot -c command to test a configuration’s IPC needs. The values of the following parameters affect the IPC needs of an application:

MAXACCESSERS
REPLYQ
RQADDR (that allows MSSQ sets to be formed)
MAXSERVERS
MAXSERVICES
MAXGTT

The following table describes the system parameters that affect the IPC needs of an application.

Table 4-5 Tuning IPC Parameters

Parameter (s) Action

MAXACCESSERS Equals the number of semaphores. Number of message queues is almost equal to MAXACCESSERS + the number of servers with reply queues (the number of servers in MSSQ set + the number of MSSQ sets).

Parameter (s)	Action
`MAXACCESSERS`	Equals the number of semaphores. Number of message queues is almost equal to `MAXACCESSERS +` the number of servers with reply queues (the number of servers in `MSSQ set +` the number of `MSSQ` sets).
`MAXSERVERS,MAXSERVICES,` and `MAXGTT`	While `MAXSERVERS`, `MAXSERVICES`, `MAXGTT`, and the overall size of the `ROUTING`, `GROUP`, and `NETWORK` sections affect the size of shared memory, an attempt to devise formulas that correlate these parameters can become complex. Instead, simply run `tmboot -c` or `tmloadcf -c` to calculate the minimum IPC resource requirements for your application.
Queue-related kernel parameters	Require to be tuned to manage the flow of buffer traffic between clients and servers. The maximum total size of a queue in bytes must be large enough to handle the largest message in the application, and to typically be 75 to 85 percent full. A smaller percentage is wasteful. A larger percentage causes message sends to block too frequently. Set the maximum size for a message to handle the largest buffer that the application sends. Maximum queue length (the largest number of messages that are allowed to sit on a queue at once) must be adequate for the application’s operations. Simulate or run the application to measure the average fullness of a queue or its average length. This may be a trial and error process in which tunables are estimated before the application is run and are adjusted after running under performance analysis. For a large system, analyze the effect of parameter settings on the size of the operating system kernel. If unacceptable, reduce the number of application processes or distribute the application to more machines to reduce `MAXACCESSERS`.

MAXSERVERS,MAXSERVICES,

and MAXGTT

While MAXSERVERS, MAXSERVICES, MAXGTT, and the overall size of the ROUTING, GROUP, and NETWORK sections affect the size of shared memory, an attempt to devise formulas that correlate these parameters can become complex. Instead, simply run tmboot -c or tmloadcf -c to calculate the minimum IPC resource requirements for your application.

Queue-related kernel parameters

Require to be tuned to manage the flow of buffer traffic between clients and servers. The maximum total size of a queue in bytes must be large enough to handle the largest message in the application, and to typically be 75 to 85 percent full. A smaller percentage is wasteful.

A larger percentage causes message sends to block too frequently.

Set the maximum size for a message to handle the largest buffer that the application sends.

Maximum queue length (the largest number of messages that are allowed to sit on a queue at once) must be adequate for the application’s operations.

Simulate or run the application to measure the average fullness of a queue or its average length. This may be a trial and error process in which tunables are estimated before the application is run and are adjusted after running under performance analysis.

For a large system, analyze the effect of parameter settings on the size of the operating system kernel. If unacceptable, reduce the number of application processes or distribute the application to more machines to reduce MAXACCESSERS.

Parent topic: Tuning CORBA Applications