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Data processing system and method with central processing unit-determined peripheral device service
| Details |
Inventors: Delorme, Alexandre;
Assignee: Hewlett-Packard Company (Palo Alto, CA)
Primary Examiner: Lee; Thomas C.
Assistant Examiner: Perveen; Rehana
Attorney, Agent or Firm:
Data processing apparatus is described comprising a processor and at least one peripheral device. The processor is arranged to service the peripheral device either in an interrupt mode in which the peripheral device is serviced in response to interrupt signals generated by the peripheral device or in a timed mode in which the peripheral device is periodically polled and serviced if required. The apparatus has a dynamic switching arrangement for switching from the interrupt mode to the timed mode depending upon conditions dynamically determined within the apparatus, at least one of said conditions being that the rate at which the peripheral device generates interrupt signals exceeds a predefined or programmable threshold frequency. The rate of polling in the timed mode is less than the threshold frequency. Thus, dynamic switching between a interrupt driven mode and a timed mode is used in order to make more efficient use of shared system resources by servicing peripheral devices only periodically at times of high demand. |
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DETAILED DESCRIPTION This invention provides a data processing system of the above described type characterised in that the rate of polling in the timed mode is less than the threshold frequency.
In this way, the load on the processor caused by frequent interrupts is reduced.
Thus, dynamic switching between a interrupt driven mode and a timed mode is not used in order to reduce latency, but rather in order to make more efficient use of shared system resources by servicing peripheral devices only periodically at times of high demand.
Such an approach is particularly suitable for Input/Output (I/O) devices which exhibit a wide variation over time in the level of service they require.
In preferred embodiments, the apparatus is arranged to handle, if required, a plurality of service events in each cycle in the timed mode.
In this way, the overall number of service events handled is not reduced, rather the handling of the events is scheduled so as to make more efficient use of shared system resources.
In this case, the dynamic switching arrangement can be arranged to switch from the timed mode to the interrupt mode when the number of service events handled within each polling cycle falls below a predefined or programmable threshold.
In one embodiment, the dynamic switching arrangement is arranged to measure the number of service events within each polling cycle and to switch to the interrupt mode when the number of service events handled within each polling cycle is below a predefined or programmable threshold for a predefined or programmable number of consecutive cycles.
Similarly, the dynamic switching arrangement can be arranged, when in the interrupt mode, to measure the time interval between each interrupt and to switch to the timed mode when the time interval between each interrupt is below a predefined or programmable threshold for a predefined or programmable number of consecutive received interrupts.
In one application for which the above technique is particularly suited, the peripheral device is a network adapter including a buffer memory and means to receive and store in the buffer memory frames of data received from a data communications network
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Multiplexer-related 
