SCHDOFLS parameter: Difference between revisions
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On a z/OS system, <var class="product">Model 204</var> [[Performance monitoring and tuning#Offloading Model 204 work to zIIP_processors|zIIP support]] enables you to offload <var class="product">Model 204</var> work from regular processors to zIIP processors. <var>SCHDOFLS</var> specifies both of the following: </p> | On a z/OS system, <var class="product">Model 204</var> [[Performance monitoring and tuning#Offloading Model 204 work to zIIP_processors|zIIP support]] enables you to offload <var class="product">Model 204</var> work from regular processors to zIIP processors. <var>SCHDOFLS</var> specifies both of the following: </p> | ||
<ul> | <ul> | ||
<li>The target number of threads on the zIIP offload queue before a non-SRB MP subtask is dispatched to help the zIIP subtasks. </li> | <li>The target number of threads on the zIIP offload queue before a non-SRB <var>[[MP/204#Multiprocessing_.28MP.2F204.29|MP]]</var> subtask is dispatched to help the zIIP subtasks. </li> | ||
<li>If started, how aggressively non-SRB MP subtasks pick up work from the zIIP offload queue. </li> | <li>If started, how aggressively non-SRB MP subtasks pick up work from the zIIP offload queue. </li> | ||
Revision as of 11:44, 24 May 2017
Threshold for task stealing zIIP work
Summary
- Default value
- 2
- Parameter type
- System
- Where set
- On User 0's parameter line or reset by system manager.
- Related products
- M204 HPO
- Introduced
- Model 204 V7.7
Description
This parameter applies to z/OS only.
On a z/OS system, Model 204 zIIP support enables you to offload Model 204 work from regular processors to zIIP processors. SCHDOFLS specifies both of the following:
- The target number of threads on the zIIP offload queue before a non-SRB MP subtask is dispatched to help the zIIP subtasks.
- If started, how aggressively non-SRB MP subtasks pick up work from the zIIP offload queue.
Setting a higher value of SCHDOFLS makes the non-SRB MP subtasks more reticent to help SRB subtasks out, ensuring better zIIP offload (though possibly adversely affecting performance should the zIIPs get overloaded).
The default value, 2, means that if all zIIP subtasks are active and there are more than SCHDOFLS * AMPSUBZ units of work on the zIIP offload queue, a non-SRB MP subtask is dispatched as needed and performs work intended for zIIPs.
SCHDOFLS has no effect if any of these is true:
- zIIP SRBs are not in use in an Online (NMPSUBZ is 0).
- The number of active SRBs (AMPSUBZ) is set to 0.
- MP subtasks are not allowed to take work from zIIPs (SCHDOPT X'40' is set).
SCHDOFL and SCHDOFLZ control the scheduling of MP and SRB (zIIP) subtasks.