You are here: Appendices > Appendix D Adjusting Default Limits
Appendix D Adjusting Default Limits
Moab is distributed in a configuration capable of supporting multiple architectures and systems ranging from a few processors to several thousand processors. However, in spite of its flexibility, for performance reasons, it still contains a number of default object limits parameters and static structures defined in header files. These limits constrain such things as the maximum number of jobs, reservations, and nodes that Moab can handle and are set to values that provide a reasonable compromise between capability and memory consumption for most sites. However, many site administrators want to increase some of these settings to extend functionality, or decrease them to save consumed memory. The most common parameters are listed in what follows. Parameters listed in the Moab configuration file (moab.cfg) can be modified by restarting Moab. To change parameters listed in moab.h, please contact technical support.
| CLIENTMAXCONNECTIONS
|
| Location |
moab.cfg (dynamic parameter) |
| Default |
128 |
| Max tested |
--- |
| Description |
Maximum number of connections that can simultaneously connect to Moab. See CLIENTMAXCONNECTIONS for additional information on this parameter. |
| JOBMAXNODECOUNT
|
| Location |
moab.cfg (dynamic parameter) |
| Default |
1024 |
| Max tested |
8192 |
| Description |
Maximum number of compute nodes that can be allocated to a job. After changing this parameter, Moab must be restarted for changes to take effect. The value cannot exceed that of the MAXNODE parameter (specified in moab.cfg). If you specify a value higher than the limit set for the MAXNODE parameter, the value will match MAXNODE. JOBMAXNODECOUNT can also be specified within configure using --with-maxjobsize=<NODECOUNT>. See JOBMAXNODECOUNT for additional information on this parameter.
|
| JOBMAXTASKCOUNT |
| Location |
moab.cfg (dynamic parameter) |
| Default |
32768 |
| Max tested |
250000 |
| Description |
Total number of tasks allowed per job. See JOBMAXTASKCOUNT for additional information on this parameter. |
| MAXGRES |
| Location |
moab.cfg (dynamic parameter) |
| Default |
512 |
| Max tested |
--- |
| Description |
Total number of distinct generic resources that can be managed. See MAXGRES for additional information on this parameter. |
| MAXJOB |
| Location |
moab.cfg (dynamic parameter) |
| Default |
51200 |
| Max tested |
500,000 |
| Description |
Maximum number of jobs that can be evaluated simultaneously. (Can also be specified within configure using --with-maxjobs=<JOBCOUNT>.) See MAXJOB for additional information on this parameter. |
| MAXNODE |
| Location |
moab.cfg (dynamic parameter) |
| Default |
5120 |
| Max tested |
160000 |
| Description |
Maximum number of compute nodes supported. See MAXNODE for additional information on this parameter. |
| MAXRSVPERNODE
|
| Location |
moab.cfg (dynamic parameter) |
| Default |
64 |
| Max tested |
1024 |
| Description |
Maximum number of reservations a node can simultaneously support. See MAXRSVPERNODE for additional information on this parameter. |
| MMAX_ATTR |
| Location |
moab.h
|
| Default |
128 |
| Max tested |
512 |
| Description |
Total number of distinct node attributes (PBS node attributes/LL node features) that can be tracked. |
| MMAX_CLASS |
| Location |
moab.h
|
| Default |
24 |
| Max tested |
64 |
| Description |
Total number of distinct job classes/queues available. |
| MMAX_FSDEPTH |
| Location |
moab.h
|
| Default |
24 |
| Max tested |
32 |
| Description |
Number of active fairshare windows. |
| MMAX_PAR |
| Location |
moab.h
|
| Default |
32 |
| Max tested |
32 |
| Description |
Maximum number of partitions supported. |
| MMAX_QOS |
| Location |
moab.h
|
| Default |
128 |
| Max tested |
128 |
| Description |
Total number of distinct QoS objects available to jobs. |
| MMAX_RACK |
| Location |
moab.h
|
| Default |
200 |
| Max tested |
200 |
| Description |
Total number of distinct rack objects available within cluster. |
| MMAX_RANGE |
| Location |
moab.h
|
| Default |
2048 |
| Max tested |
2048 |
| Description |
Total number of distinct timeframes evaluated.
This is proportional to the size of the cluster and the number of simultaneously active jobs in the cluster. (Can be specified within ./configure using --with-maxrange=<RANGECOUNT>.) Increasing this value will not increase the size of total memory consumed by Moab but may result in minor slowdowns in the evaluation and optimization of reservations.
|
| MMAX_REQ_PER_JOB |
| Location |
moab.h
|
| Default |
5 |
| Max tested |
64 |
| Description |
Total number of unique requirement structures a job can have. Limits the number of -w clauses in the mshow -a command. It also limits the number of -l nodes=X+Y+Z a normal HPC job can have. |
Moab currently possesses hooks to allow sites to create local algorithms for handling site specific needs in several areas. The contrib directory contains a number of sample local algorithms for various purposes. The MLocal.c module incorporates the algorithm of interest into the main code. The following scheduling areas are currently handled via the MLocal.c hooks.
- Local Job Attributes
- Local Node Allocation Policies
- Local Job Priorities
- Local Fairness Policies
Related Topics
Appendix I: Considerations for Large Clusters