Resource Priorities

What's Resource Priority

When a job is submitted to a GridLink farm, it is assigned a "resource priority" by the user. A "resource priority" may be one of the following:

• Urgent
• High
• Normal
• Low
• No Helpers

This priority is mainly used for farms with multiple job queues. When more than one distributable jobs running in multiple job queues, the farm will be split automatically based on each job's resource priority. A job with higher resource priority will receive more helpers. If the user doesn't need any helper to help this job, he/she can simply specify the priority as "No Helpers".

If the farm administrator wishes to limit the resource priority for jobs submitted by a user, he/she can specify a "Maximum Resource Priority" for this user. e.g. once it's specified as "low", all jobs submitted by this user will not get a priority higher than "low". If the administrator doesn't want to have any priority limit on a user, he/she can simply specify this setting as the maximum one ("urgent"). It is "high" by default.

After the job has been submitted, before it is finished, you can always right click on the job from the remote job list in the Job Monitor, and use the menu "Change Resource Priority" to change the priority. The farm will be rebalanced after this.

Resource Priority Ratio

The ratios for different priorities can be customized by the user from "Advanced (GridLink)" tab in "Farm Settings" dialog in GridLink Utility. By default, the ratios are:

Urgent:	100
High:	50
Normal:	25
Low:	5

e.g. if a job in one job queue has "high" priority, the other job in another job queue has "low" priority and there are 32 CPU cores on the farm, then GridLink will assign 27 helpers to job 1 (total 28 CPU cores) and 3 helpers to job 2 (total 4 CPU cores).

Urgent Resource Priority

As explained previously, a resource priority is mainly used for farms with multiple job queues. If the user has only one job queue, it doesn't make any difference to use "High", "Normal" or "Low" priority. However, 2 priorities - "No Helpers" and "Urgent" - can be very useful. "No Helpers" is self-explanatory, which means this job will be run by the master only. We will discuss the powerful "Urgent" priority in more details.

Usually, if you submit 2 distributable jobs with "Normal" priority to one job queue, the first one will be started right away, and the second one will be pending until the first job is finished. However, If you urgently need the results from the second job and want it to be started right away, there's a way to do it. This is to assign "Urgent" priority to the second job.

When an "Urgent" job is submitted, even if there’s another distributable job (non-urgent) is running in the same job queue, the urgent job will start right away as long as the master server has multiple CPU cores and multiple jobs are permitted to run simultaneously on the farm. Once started, the urgent job will take away all helpers that were helping the other job. The non-urgent job will run by the master alone until the urgent job is done.

Also, the "Urgent" priority has higher resource ratio than other priorities. In the case of multiple job queues, an urgent job will get much more helpers than other non-urgent jobs on the whole farm

Resource Priority in Older AXIS Versions

We started to let GridLink start helpers since 11.4.03.001, but the concept of "Resource Priority" was not introduced until 11.5.01.001. However, the user can still take advantage of this feature with a version between 11.4.03.001 and 11.5.01.001.

When submitting a job, the user will see the "Helpers Requested" section on the dialog, instead of "Resource Priority". The user can also see the maximum number of helpers on the farm, suppose it is N.

If the user requests the number of helpers as 0, then it is equivalent to "No Helpers".

If it's less than N/3, then it is equivalent to "Low".

If it's greater than or equal to N/3, but less than 2*N/3, then it is equivalent to "Normal".

If it's greater than or equal to 2*N/3, or "Request maximum helpers available on the farm" is selected, then it is equivalent to "High".

After the job is submitted and you want to change the priority, you can do it with a later AXIS version.