63 lines
2.2 KiB
Markdown
63 lines
2.2 KiB
Markdown
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# Part model
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Ovni has a model to represent the hardware components as well as the software
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concepts like threads or processes. Each concept is considered to be a *part*.
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Here is an example diagram depicting the part hierarchy:
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Notice how a loom can restrict the CPUs of the node to its child processes.
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## Software parts
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These are not physical parts, but they abstract common concepts.
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### Thread
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A thread in ovni is directly mapped to a [POSIX
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thread](https://en.wikipedia.org/wiki/Pthreads) and they are identified by a
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`TID` which must be unique in a [node](#node). Threads in ovni have [a model with
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an internal state](../emulation/ovni.md/#thread_model) that tries to tracks the
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state of the real thread.
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### Process
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A process is directly mapped to a UNIX
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[process](https://en.wikipedia.org/wiki/Process_(computing)) and they are
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identified by a `PID` number which must be unique in a [node](#node).
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### Loom
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A loom has no direct mapping to a usual concept. It consists of a set of
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[CPUs](#cpu) from the same node and a set of processes that can *only run in
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those CPUs*. Each CPUs must belong to one and only one loom. It is often used
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to group CPUs that belong to the same process when running workloads with
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multiple processes (like with MPI).
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Each loom has a virtual CPU which collects running threads that are not
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exclusively assigned to a physical CPU, so we cannot determine on which CPU they
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are running.
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## Hardware parts
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These parts have a physical object assigned.
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### CPU
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A CPU is a hardware thread that can execute at most one thread at a time. Each
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CPU must have a physical ID that is unique in a node. In ovni there is also a
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virtual CPU, which simply is used to collect threads that are not tied to an
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specific physical CPU, so it cannot be easily determined where they are running.
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### Node
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A *node* refers to a compute node, often a physical machine with memory and
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network which may contain one or more
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[sockets](https://en.wikipedia.org/wiki/CPU_socket), where each socket has one
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or more CPUs.
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### System
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A system represents the complete set of hardware parts and software parts that
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are known to ovni in a given trace.
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