Changeset 4a2d728 for doc/theses/thierry_delisle_PhD
- Timestamp:
- Sep 9, 2022, 6:19:54 PM (2 years ago)
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- ADT, ast-experimental, master, pthread-emulation
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- 35ece70, b0ceb72
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- 62424af2
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doc/theses/thierry_delisle_PhD/thesis/glossary.tex
r62424af2 r4a2d728 17 17 {name={Thread},text={thread}} 18 18 { 19 A bstract object representing a unit of work. Systems will offer one or more concrete implementations of this concept (\eg \gls{kthrd}, \gls{job}), however, most of the concepts of scheduling are independent of the particular implementations of the work representation. For this reason, this document uses the term \Gls{at} to mean any representation and not one in particular.19 A thread is an independent sequential execution path through a program. Each thread is scheduled for execution separately and independently from other threads. A thread must have its own stack to save its state when it is scheduled. Systems offer one or more concrete implementations of this concept, \eg \gls{kthrd}, \gls{job}, task. However, most of the concepts of scheduling are independent of the particular implementations of the thread representation. For this reason, this document uses the term \gls{at} to mean any of these representation that meets the general definition. 20 20 21 21 \textit{Synonyms : Tasks, Jobs, Blocks.} … … 25 25 {name={Processor},text={processor}} 26 26 { 27 Entity that executes the \glspl{at}, \ie the resource being scheduled by the scheduler. In kernel level threading, \ats are kernel threads and \procs are the \glspl{hthrd} on which the kernel threads are scheduled. In user-level threading and inthread pools, \procs are kernel threads.27 Entity that executes a \gls{at}, \ie the resource being scheduled by the scheduler. In kernel-level threading, \ats are kernel threads and \procs are the \glspl{hthrd} on which the kernel threads are scheduled. In user-level threading and thread pools, \procs are kernel threads. 28 28 29 29 \textit{Synonyms : Server, Worker.} … … 33 33 {name={Ready Queue}, text={ready-queue}} 34 34 { 35 Data structure holding \ats that are ready to be \glslink{atrun}{run}. Often a \glsxtrshort{fifo} queue, but can take many different forms, \eg binary treesare also common.35 Data structure holding \ats that are ready to \glslink{atrun}{run}, but currently all the processors are in use. Often a \glsxtrshort{fifo} queue for fairness, but can take many different forms, \eg binary tree and priority queue are also common. 36 36 } 37 37 38 38 \longnewglossaryentry{uthrding} 39 {name={User-Level Threading},text={user-level threading}}39 {name={User-Level \Gls{at}ing},text={user-level threading}} 40 40 { 41 Threading model where a scheduler runs in users space and maps threads managed and created inside the user-space onto \glspl{kthrd}.41 \Gls{at}ing model where a scheduler runs in users space and maps threads managed and created inside the user-space onto \glspl{kthrd}. 42 42 43 43 \textit{Synonyms : User threads, Lightweight threads, Green threads, Virtual threads, Tasks.} … … 47 47 {name={Remote Memory Reference},text={remote memory reference}} 48 48 { 49 Reference to an address in memory that is considered \newterm{remote}, as opposed to \emph{local}. This can mean for example: a cache line that is in a cache not shared by the current \gls{hthrd}, a block of memory that belons to a different CPU socket in a \glsxtrshort{numa} context, etc.49 A memory reference to an address not in the current \gls{hthrd}'s L1 or L2 cache is a remote reference. L1 and L2 cache references are considered \emph{local}. For example, a cache line that must be updated from the L3 cache or from any cache on another socket, or from RAM in a \glsxtrshort{numa} context. 50 50 } 51 51 … … 53 53 54 54 \longnewglossaryentry{hthrd} 55 {name={Hardware Thread},text={hardware thread}}55 {name={Hardware \Gls{at}},text={hardware thread}} 56 56 { 57 Threads representing the underlying hardware directly, \eg the CPU core, or hyper-thread if the hardware supports multiple threads of execution per core. The number of hardware threads is considered to be always fixed to a specific number determined by the hardware.57 \Gls{at}s representing the underlying hardware, \eg a CPU core or hyper-thread, if the hardware supports multiple threads of execution per core. The maximum number of hardware threads is fixed on any given computer. 58 58 59 \textit{Synonyms : Core, Processing Unit, CPU.}59 \textit{Synonyms : Core, Hyper-\Gls{at}, Processing Unit, CPU.} 60 60 } 61 61 62 62 \longnewglossaryentry{kthrd} 63 {name={Kernel-Level Thread},text={kernel-level thread}}63 {name={Kernel-Level \Gls{at}},text={kernel-level thread}} 64 64 { 65 Threads created and managed inside kernel-space. Eachthread has its own stack and its own thread of execution. Kernel-level threads are owned, managed and scheduled by the underlying operating system.65 \Gls{at}s created and managed inside kernel space. Each kernel thread has its own stack and its own thread of execution. Kernel-level threads are owned, managed and scheduled by the underlying operating system. 66 66 67 67 \textit{Synonyms : OS threads, Hardware threads, Physical threads.} … … 71 71 {name={Fiber},text={fiber}} 72 72 { 73 Fibers are non-preemptive user-level threads. They share most of the c aracteristics of user-level threads except that they cannot be preempted by another fiber.73 Fibers are non-preemptive user-level threads. They share most of the characteristics of user-level threads except that they cannot be preempted by another fiber. 74 74 75 75 \textit{Synonyms : Tasks.} … … 85 85 86 86 \longnewglossaryentry{pool} 87 {name={ ThreadPool},text={thread-pool}}87 {name={\Gls{at} Pool},text={thread-pool}} 88 88 { 89 Group of homogene uous threads that loop executing units of works. Often executing \glspl{jobs}.89 Group of homogeneous threads that loop executing units of works. Often executing \glspl{jobs}. 90 90 91 91 \textit{Synonyms : Executor.} … … 103 103 {name={Scheduling a \gls{at}}} 104 104 { 105 Scheduling a \at refers to the act of notifying the scheduler that a task is ready to be run. When representing the scheduler as a queue of tasks, scheduling is the act of pushing a task onto the end of the queue. This does not necessarily mean the task will ever be allocated CPU time (\gls{atrun}), for example, if the system terminates abruptly, scheduled \glspl{at} will probablynever run.105 Scheduling a \at refers to notifying the scheduler that a \at is ready to run. When representing the scheduler as a queue of \ats, scheduling is the act of pushing a \at onto the end of the queue. This operation does not necessarily mean the \at is guaranteed CPU time (\gls{atrun}), \eg if the program terminates abruptly, scheduled \glspl{at} never run. 106 106 107 107 \textit{Synonyms : Unparking.} … … 111 111 {name={Running a \gls{at}}} 112 112 { 113 Running a \at refers to the act of allocating CPU time to a task that is ready to run. When representing the scheduler as a queue of tasks, running is the act of popping a taskfrom the front of the queue and putting it onto a \gls{proc}. The \gls{at} can then accomplish some or all of the work it is programmed to do.113 Running a \at refers to allocating CPU time to a \at that is ready to run. When representing the scheduler as a queue of \ats, running is the act of popping a \at from the front of the queue and putting it onto a \gls{proc}. The \gls{at} can then accomplish some or all of the work it is programmed to do. 114 114 115 115 \textit{Synonyms : None.} … … 117 117 118 118 \longnewglossaryentry{atmig} 119 {name={ Migration of \glspl{at}}}119 {name={\Glspl{at} Migration}} 120 120 { 121 Migration refers to the idea of an \gls{at} running on a different \proc than the last time it was run. It is generally preferable to minimi se migration as it incurs cost but any load balancing among \proc requires some amount of migration.121 Migration refers to the idea of an \gls{at} running on a different \proc than the last time it was run. It is generally preferable to minimize migration as it incurs cost but any load balancing among \proc requires some amount of migration. 122 122 123 123 \textit{Synonyms : None.} … … 133 133 134 134 \longnewglossaryentry{atblock} 135 {name={ Blocking an \gls{at}}}135 {name={\Gls{at} Blocking}} 136 136 { 137 Blocking an abstract task refers to the act of taking a task that us running on a CPU off the CPU. Unless no other task is ready, this action is generally immediately followed by running an other task.137 \Gls{at} blocking means taking a running \at off a CPU. Unless no other \at is ready, this action is immediately followed by running another \at. 138 138 139 139 \textit{Synonyms : Parking.} … … 143 143 {name={Running to completion}} 144 144 { 145 Running to completion refers to the entire sequence of : being scheduled, running and blocking, for a given task.145 Running to completion refers to the entire sequence of : being scheduled, running and blocking, for a given \at. 146 146 147 147 See also \gls{atsched}, \gls{atrun}, \gls{atblock} … … 153 153 {name={System Load},text={load}} 154 154 { 155 The System Load refers to the rate at which \glspl{at} are \glslink{atsched}{scheduled} versus the rate at which they are \glslink{atrun}{run}. When \glspl{at} are being scheduled faster than they are run, the system is considered \emph{overloaded}. When \glspl{at} are being run faster than they are scheduled, the system is considered \emph{underloaded}. Conrrespondingly, if both rates are equal, the system is considered \emph{loaded}. Note that the system is considered loaded only of the rate at which \glspl{at} are scheduled/run is non-zero, otherwise the system is empty,it has no load.155 The system load refers to the rate at which \glspl{at} are \glslink{atsched}{scheduled} versus the rate at which they are \glslink{atrun}{run}. When \glspl{at} are being scheduled faster than they are run, the system is considered \emph{overloaded}. When \glspl{at} are being run faster than they are scheduled, the system is considered \emph{underloaded}. Correspondingly, if both rates are equal, the system is considered \emph{loaded}. Note the system is considered loaded only if the rate at which \glspl{at} are scheduled/run is non-zero, otherwise the system is empty, \ie it has no load. 156 156 157 157 \textit{Synonyms : CPU Load, System Load.}
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