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Overview
SmartShare is a feature where in which the system automatically expands job instances to fill up idle, or "surplus", worker job slots. The expansion is automatically balanced among jobs, so that each job gets an equal number of surplus job slots.
Jobs have a 'max_cpus' value which puts an upper limit on how wide a single job can expand. This value can be supplied via a site-wide default or specified on a job-by-job basis.
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SmartShare
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Disabling SmartShare
To opt out, the site administrator can set the supervisor_smart_share_mode to "none" in qb.conf on the supervisor machine:
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supervisor_smart_share_mode = none
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SmartShare from a user's perspective
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It is possible to control how much a job automatically expands, on a job-by-job basis, by setting a new job attribute called "max_cpus" at submission. This value sets an upper limit to the number of instances to which the job will expand. The max_cpus parameter is only visible in the submission UI when in Expert Mode. If an end-user does nothing, their job will expand as wide widely as the system administrator has allowed (as specified in the various supervisor_*_max_cpus_* settings); the defined (see Configuring SmartShare, below). The administrator can specify a default and a maximum value for max_cpus.
Jobs will expand to their max_cpus value if there are enough empty slots on the farm. As other users begin to submit jobs as well, a user's job will shrink to allow for a more "balanced" usage of the farm between jobs. No job will shrink below its "instance count" (or "
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CPUs") value.
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For example, a job submitted from the command line "qbsub" utility as in :
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$ qbsub -priority
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5
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-cpus
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10
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-max_cpus
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50
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-range
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1-100
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sleep
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60
ends up with 10 primary instances as specified by the "cpus" option at priority 5, and may expand up to 50 instances if surplus job slots are available. In other words, as many as 40 secondary instances will be dispatched, at a lower priority. "
Settings
- Setting
max_cpus
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- to "*" (asterisk) or a negative number, such as "-1",
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- means "no limit", which will allow the job to expand to the
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- setting. This is configured by the site administrator.
- Setting
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max_cpus
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- to 0
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- disables SmartShare for the job.
- If
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max_cpus
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- is unspecified at submission, the system will apply the default value, which is
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-
supervisor_default_max_cpus. This is configured by the site administrator. - The
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max_cpus
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- value may also be modified after submission,
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- in the GUI, with the qbmodify command, or via the API.
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Priorities
- The instances that were automatically expanded by SmartShare ("secondary instances") run at low priority, and are the first subject to
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- pre-emption in order to run primary instances from other jobs. Secondary instances may also be
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- pre-empted in order to run secondary instances from other jobs, to balance the number of secondary instances among all jobs.
- The method of
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- pre-emption can either be "aggressive", meaning the instance is immediately terminated, or "passive", meaning the instance is allowed to finish processing the current agenda item before terminating, and is configured by the site
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- administrator (see
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- below).
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- The default smart share
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- pre-emption mode is "aggressive"; secondary instances will be stopped immediately in order to accomplish the balancing of jobs as quickly as possible
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Configuring SmartShare
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