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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.
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
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
INTERRUPT HANDLING MIGRATION(IHM)
• Basic Concept of IHM:
(a) original case, (b) when interrupt handler thread is applied.(c) when IHM is applied.
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Basic Operation of IHM:Continued…
IIIT,Hyderabad 09/12/2011
• 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
Operation of IHM under Multiple Waiting Processes:
Continued…
IIIT,Hyderabad 09/12/2011
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.
DIRECT INTERRUPT SCHEDULING (DIS)
Basic Concept of DIS:
IIIT,Hyderabad 09/12/2011
Operation of DIS:
Continued…
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IIIT,Hyderabad 09/12/2011
(Implemented based on the Linux 2.6.19 kernel source code)
Pseudo code for IHM
Implementation
IIIT,Hyderabad 09/12/2011
Pseudocode for DIS:
Continued…
IIIT,Hyderabad 09/12/2011
Additional Considerations for the Implementation:
Deferring address space switching. Support for SMP.
Continued…
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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
IIIT,Hyderabad 09/12/2011