This chapter describes formats for PE files created and
edited by system administrators (in /etc).
Certain applications can benefit from enhanced dispatching priority
during execution. POE provides a service for periodically adjusting the
dispatching limits of a user's task between set limits. The
service is specified by entries in the file
/etc/poe.priority, as described below. Each record in
the file associates a set of dispatching parameters (high and low priorities,
duty factor, and adjustment period) with each user authorized to use this
service. The user specifies which service entry to use by setting the
MP_PRIORITY environment variable prior to invoking POE. There is no
The range of parameters permitted in the adjustment record is purposely set
to be as unrestricted as possible. The user and system administrator
(who owns the configuration file) must evaluate the effect of various
parameter settings in their own operating environment. Carefully read
the notes accompanying the file format description. The following are
descriptions of the parameters.
- name of user
- name assigned to class - user selects class with POE environment variable
- the dispatching priority assigned to the favored portion of the cycle
- the dispatching priority assigned to the rest of the cycle
- the portion of the cycle at which the job is at hipriority (percent)
- length of adjustment cycle, in seconds
- The normal AIX dispatching priority is 60. If both
hipriority and lopriority are set to values less than
60, a compute bound job will prevent other users from being dispatched.
- The hipriority value must be equal to or greater than
12. If the value is between 12 and 20, the job competes with system
processes for cycles, and may disrupt normal system activity.
- If hipriority value is less than 30, keystroke capture will be
inhibited during the hipriority portion of the dispatch
- If hipriority is less than 16, the job will not be subject to
the AIX scheduler during the high priority portion of the cycle.
- The lopriority value must be less than or equal to 127.
- If the hipriority value is less than (more favored than) the
priority of the SP Switch fault-service daemon, and if the low priority portion of the
adjustment cycle is less than two seconds, then switch fault recovery will be
unsuccessful, and the node will be disconnected from the switch.
- The priority adjustment process allows programs using the User Space
access to the SP Switch to maximize their effectiveness in interchanging data. The
process may also be used for programs using IP, either over the switch or over
another supported device. However, if the high priority phase of the
user's program is more favored than the network processes (typically
priorities 36-39), the required IP message passing traffic may be blocked and
cause the program to hang.
- Consult the include file /usr/include/sys/pri.h for
definitions of the priorities used for normal AIX functions.
- The parameter file /etc/poe.priority defines the
scheduling parameters for tasks running on that node. Each node may
have a different priority file.
- The primary performance enhancement is achieved when the user's
application can run with minimal interference from the standard AIX daemons
running on each node. This is achieved when the user's application
is scheduled with a fixed priority more favored than the daemons, which
typically run with a priority setting of 60.
- Status and error messages generated during the priority adjustment process
are written to the file /tmp/pmadjpri.log. Also, any
error or diagnostic information from POE's invocation of the priority
adjustment function will be recorded in the partition manager log (controlled
by the POE MP_PMDLOG environment variable and -pmdlog
userfoo super 12 64 95 10
userfoo sponge 64 120 50 30
edgar default 20 64 95 10
edgar normal 60 60 50 20
The optional /etc/poe.limits file enables
the system administrator to override the default values for certain POE
This is useful in cases where the environment variable default values might
cause problems on a particular node. For example, if a node had only
64M of real memory, the default value of 64M for MP_BUFFER_MEM would
be too high; to correct this problem, the system administrator would specify a
lower value for MP_BUFFER_MEM in the /etc/poe.limits
file on that node.
Entries in the /etc/poe.limits file must be in the
supported_object = value
where supported_object is currently limited to
MP_BUFFER_MEM, MP_AUTH, and
|Note:||Any line in the file with the character # or ! in the first
column is treated as a comment.
If the /etc/poe.limits file has been set up on a
particular node, the Partition Manager daemon (pmdv2) on that
- compares the values specified in the /etc/poe.limits file
against the environmment variables received from the home node
- if necessary, resets the environment variables as follows:
If the value in the environment exceeds the value specified in
/etc/poe.limits, then pmdv2 resets the value to that
If the value in the environment is different from the value
specified in /etc/poe.limits, then pmdv2 resets the
value to that in /etc/poe.limits.
If the value in the file is yes and POE determines that the job is
not being run under LoadLeveler, the job is terminated. Setting the
value to no has no effect.
- if a supported_object is specified in
/etc/poe.limits but is not set in the environment,
sets the value to that specified in /etc/poe.limits
|Note:||If the /etc/poe.limits file contains any entries either with
unsupported objects to the left of the equal sign or with invalid (non-numeric
for MP_BUFFER_MEM, or not AIX or DFS for
MP_AUTH) values to the right, pmdv2 flags these entries in
the pmdlog for that node. pmdv2 also uses the
pmdlog to indicate when a supported_object has been set or
reset in the environment.
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