Method and apparatus for dispatching tasks requiring short-duration processor affinity

DETAILED DESCRIPTION To achieve these and other objects, this invention provides a mechanism for efficiently redispatching a task from a first processor (lacking a required resource) to a second processor (with the required resource), without requiring that the task continue to execute on the second processor after its initial dispatch there.
The MVS embodiment is to create a set of processor-related dispatcher queues, which are scanned early by a dispatcher executing in a processor ready for work.
When a task is interrupted by a program check because a resource required to execute the instruction is not on that processor, the interrupt handling mechanism suspends the task, making it ineligible to be dispatched, and enqueues an SRB on the processor-related queue for a processor having the required resource.
The processor having the resource then resumes processing of the interrupted task via the SRB RESUME mechanism (at the point of interruption) on a subsequent scan for work.
Because there is no setting of task affinity with this mechanism, there is no need to "unset" affinity--i.
e.
, the task will automatically be dispatchable on any free processor after its next interruption.
This characteristic makes the invention suitable for "transient" affinity requirements (e.
g.
, a cryptographic instruction requiring a cryptographic feature).
Typically, a task executing a crypto function (encipher/decipher) will not likely execute another such instruction "soon".
Therefore, giving the task affinity for the processor having the crypto feature unnecessarily limits the system's load balancing ability, while requiring an overt action ("unsetting" affinity) is wasteful of processing time.
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