Unknown Status on Overloaded Servers

HP Output Server 3.5 13

Solution

NOTE: For information on which attributes need to be indexed and which do not, see the readme

file located at $DAZEL_HOME/nls/oid/C/README.DPAOIDs.

Using arenas and extensionpages to allocate memory (HP-UX)

HP-UX uses arenas to allocate memory to each thread. When a request for memory is received from a new thread, the

HP-UX operating system allocates additional memory. This may lead to an increase in the memory usage for each

operation as the requests get served by different threads each time. Memory usage can increase until it exceeds the

data segment size limit that is set by the ulimit parameter.

NOTE: This limit exceeds when several pdls commands are executed on the Configuration

Manager (CM) and the CM stops responding.

This behavior of HP-UX memory allocator can be altered using the _M_ARENA_OPTS environment variable. To

control the memory growth, set the _M_ARENA_OPTS environment variable as a value of the

-server-environment-variables attribute with the config_server command. You can use

_M_ARENA_OPTS to tune the number of arenas and the extensionpages for threaded applications.

An arena is a linked list that a group of threads share. The default is 8 arenas per process. Extensionpages control the

number of pages to expand each time, assuming that the default page size used is of 4096 Bytes (4KB).

When there are more threads in an application, more arenas should be used for better performance. In general, the

more arenas you use, the smaller the extensionpages should be, and vice versa. However, this would also result in an

increase in memory usage.

The number of arenas can range from 1 to 64 for threaded applications. If the _M_ARENA_OPTS environment

variable is not set, or the number of arenas is set to be out of range, the default number of arenas used is 8. The

extensionpages is from 1 to 4096. If the extensionpages is set to be out of range, the default value of 32 is used.

For Example

export _M_ARENA_OPTS=1:8

_M_ARENA_OPTS is interpreted as:

_M_ARENA_OPTS=#arenas:#extensionpages

In the above example, arenas is the number of arena's to be used for the application while extensionpages determines

the number of pages to be expanded each time. Here the extensionpages determine by how many page sizes an arena

would grow when an arena needs more memory. Assuming that a vps_pagesize uses a default page size of 4096

Bytes (4KB), this would mean that an arena would expand with 8x4 = 32KB when it needs more memory with a

setting of _M_ARENA_OPTS=1:8.

NOTE: The default value for _M_ARENA_OPTS is 8:32

To resolve the problem of server crash due to memory issue, use a single arena and set the extensionpages based on

your requirements.

Some examples on how to prevent the overloaded servers going into an an unknown state (due to a memory issue)

are detailed below.

107

(capabilities)

__name

Server Name Table Name Indexed Attribute