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IIIT,Hyderabad 09/12/2011 INTERRUPT HANDLER MIGRATION & DIRECT INTERRUPT SCHEDULING FOR RAPID SCHEDULING OF INTERRUPT- DRIVEN TASKS JUPYUNG LEE and KYU HO PARK, Korea Advanced Institute of Science and Techn

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Its a research paper for VLSI.

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Page 1: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

IIIT,Hyderabad 09/12/2011

INTERRUPT HANDLER MIGRATION &

DIRECT INTERRUPT SCHEDULING FOR

RAPID SCHEDULING OF INTERRUPT-DRIVEN TASKSJUPYUNG LEE and KYU HO PARK,Korea Advanced Institute of Science and Technology.

Page 2: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

OS latency

Evolution of preemptibility of linux kernel

Increasing the probability that an interrupt occurs in the middle of a pre-emptible section so that a high-priority process that has been waiting for the interrupt can preempt other processes quickly. Interrupt handler thread: Problem: that it causes an additional context switch per

interrupt arrival.

One of the solution : IHM: Aims to take full advantage of the interrupt handler thread technique while avoiding the additional context switch.

INTRODUCTION

IIIT,Hyderabad 09/12/2011

Page 3: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

REDUCING OS LATENCY:

• Interrupt Handler Migration (IHM)

• Direct Interrupt Scheduling (DIS)

“Above two methods are explained in research paper. Their study focuses onlowering the interrupt handling latency, called the OS latency in this article,

Under the situation where the arrival rates of the interrupts are not high enoughto cause the receive live lock problem.” !!

• Implementation

• Experiments

IIIT,Hyderabad 09/12/2011

Page 4: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

INTERRUPT HANDLING MIGRATION(IHM)

• Basic Concept of IHM:

(a) original case, (b) when interrupt handler thread is applied.(c) when IHM is applied.

IIIT,Hyderabad 09/12/2011

Page 5: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

Basic Operation of IHM:Continued…

IIIT,Hyderabad 09/12/2011

Page 6: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

• Advantages:

Improving the cache hit ratio. Resolving the priority inversion problem. Improving interrupt accounting.

• Some problems they solved:

What happens if the interrupt handler does not actually wake up the process?

What happens if multiple processes are waiting for the same interrupt source?

What happens if a multiple number of interrupt handler threads are interposed

Between the previous process and target process?

Continued…

BACK

IIIT,Hyderabad 09/12/2011

Page 7: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

Operation of IHM under Multiple Waiting Processes:

Continued…

IIIT,Hyderabad 09/12/2011

Page 8: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

Resolving the priority inversion problem caused by IHM

Fig. 7. Examples of the interrupt-driven priority inversion problem: (a) original case, (b) when theinterrupt handler is applied, (c) when IHM is applied.

Page 9: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

DIRECT INTERRUPT SCHEDULING (DIS)

Basic Concept of DIS:

IIIT,Hyderabad 09/12/2011

Page 10: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

Operation of DIS:

Continued…

BACK

IIIT,Hyderabad 09/12/2011

Page 11: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

(Implemented based on the Linux 2.6.19 kernel source code)

Pseudo code for IHM

Implementation

IIIT,Hyderabad 09/12/2011

Page 12: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

Pseudocode for DIS:

Continued…

IIIT,Hyderabad 09/12/2011

Page 13: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

Additional Considerations for the Implementation:

Deferring address space switching. Support for SMP.

Continued…

BACK

IIIT,Hyderabad 09/12/2011

Page 14: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

IIIT,Hyderabad 09/12/2011

Conclusion:

This article, proposed two techniques that aim to minimize the scheduling latency of high-priority interrupt-driven tasks, named interrupt handler migration (IHM) and direct interrupt scheduling (DIS). These techniques are designed based on our observation that even in highly responsive fully preemptible operating systems additional room remains for further reductions in the scheduling latency

Page 15: interrupt handler migration & direct interrupt scheduling for rapid scheduling of interrupt driven tasks

IIIT,Hyderabad 09/12/2011