Flattening Hierarchical Scheduling
- Source:
- Author: Lackorzynski, Warg, Volp, Hartig
- Related: Sistemi Operativi, Microkernel Based Systems
Notes
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the objective is to integrate multiple real-time systems as guests on a single host using
VMs -
in literature there are different takes on the matter
- mismatch between embedded-systems requirements and the virtual-machine model is evident in scheduling […] the integrated nature of embedded systems requires that scheduling priorities of different subsystems must be interleaved. This is at odds with the concept of virtual machines.[
The Role of Virtualization in Embedded Systems] - some argue bandwidth servers with small and frequently replenished budgets is sufficient
- mismatch between embedded-systems requirements and the virtual-machine model is evident in scheduling […] the integrated nature of embedded systems requires that scheduling priorities of different subsystems must be interleaved. This is at odds with the concept of virtual machines.[
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the paper argues the root of the dispute lies in limitations in current virtualization technology
- a small enhancement of the scheduler in the guest task sets for the host scheduler to integrate these workloads onto a single system by interleaving
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different types of virtualization
- faithful and paravirtualization
- first needs hardware properties in the host
- second modifies the guest OS
- faithful and paravirtualization
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the approach of the paper is to attenuate the strict separation for schedulers of different
VMs- that is the host just provides a budget to guests without any other information
- this is done by having the host scheduler allocating budgets as scheduling contexts
- as the schedulability of the system is validated this is attached to the
vCPUof theVM
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interrupts are implemented as assignments of
SCto events by the host