SCHDOFL parameter

From m204wiki
Jump to navigation Jump to search

Threshold for activating subtasks

Summary

Default value
2
Parameter type
System
Where set
On User 0's parameter line or reset by system manager.
Related products
All
Introduced
Model 204 V7.4

Description

Specifies the target number of threads on the MP offload queue per active task. Setting this parameter makes the Model 204 MP subtask scheduler more responsive to instantaneous increases in load at the potential cost of starting MP subtasks too frequently incurring high wait, post, and address space dispatch costs.

The default value of 2 means that if there are more than twice as many units of MP offloadable work waiting to be processed in an MP subtask as there are active subtasks, and fewer than AMPSUBS subtasks are currently running, another MP offload subtask is activated.

SCHDOFL has no effect if MP/204 is not in effect in an Online (NMPSUBS=0) or if the number of active subtasks (AMPSUBS) is set to 0 or 1. (If AMPSUBS=1, an MP subtask is activated as soon as there is any offloadable work and then runs until there is no more offloadable work for it to process.)

The SCHDOFLZ parameter performs the same function as SCHDOFL for zIIP (SRB) subtasks and the SCHDOFLS parameter controls how aggressively MP subtasks will be started to help zIIP subtasks out and how aggressively MP subtasks will take work from zIIP subtasks.