Operation operation fast threads user topaz threads

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Unformatted text preview: eads, and processes. Operation Operation Fast Threads (user) Topaz Threads Threads (kernel) Unix Processes Null fork 34 948 11300 Signal-wait 37 441 1840 Scheduler Scheduler Activations Want best of both worlds User-space: custom-scheduling, fast Kernel-space: integrated (multiprocessing), blockable SA SA Idea: Create a structure that allows information to flow flow between: user-space (thread library) and kernel One-way is common … system call Other way is uncommon (sort of) …. Upcall SA SA Cont’d Two new things: Activation: structure that allows information/events to to flow (holds key information, e.g. stacks) Virtual Virtual processor: abstraction of a physical machine; gets “allocated” to an application -- means any threads attached to it will run on that processor --- want to run on multiple processors – ask OS for > 1 VP Example Example Kernel provides two processors to the application, user library picks picks two threads to run …. Now, suppose T1 blocks …. T1 T1 blocks in the kernel I/O for (T1) completes Notification Notification requires a processor; kernel preempts one of them (B – T2), does upcall Problem : suppose no processors! – must wait until kernel gives one Two threads back on the ready list! Example Example (done) User library picks a thread to run (resume T1) Assessment Assessment Pros: Cons: Next Next Lecture Scheduling (maybe deadlock, if time) Read Chap. 2, 6 MOS, Lottery Scheduling Paper HW #1 available Project #1 available on Friday...
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