3/31/21 ESE150 Spring 2021 OBSERVATION Ò We want our phones (and computers) to do many things at once. Ò If we dedicate a processor to MP3 decoding É It will sit idle most of the time Ò MP3 decoding (and many other things) do not consume a modern processor Lecture #18 – Operating Systems (OS) Ò Idea: Maybe we can share the processor among ESE 150 – tasks? DIGITAL AUDIO BASICS ESE150 Spring 2021 Based on slides © 2009--2021 DeHon 1 2 ESE150 Spring 2021 ESE150 Spring 2021 BIG IDEA OUTLINE Ò Provide the illusion of (virtually) unlimited Ò Review processors by sharing single processor in time Ò Worksheet: Virtualization In Action Ò Strategy É Time-share processor Ð Store all process (virtual processors) state in memory Ð Iterate through processes × Restore process state × Run for a number of cycles × Save process state 3 4 ESE150 Spring 2021 ESE150 Spring 2021 COURSE MAP – WEEK 10 ROLE OF OPERATING SYSTEM MIC Ò Higher-level, shared support for all programs A/D É Could put it in program, but most programs need it! É Needs to be abstracted from program Music 1 domain conversion 5,6 compress Ò ResourCe sharing Numbers É Processor, memory, “devices” (net, printer, audio) correspond to pyscho- course weeks sample freq Ò acoustics 3 Polite sharing 2 4 É Isolation and protection EULA É Fences make Good Neighbors – R. Frost -------- D/A 10101001101 -------- Ò Idea: Expensive/limited resources can be shared in click time – OS manages tHis sHaring OK speaker MP3 Player / iPhone / Droid 5 6 1 3/31/21 ESE150 Spring 2021 ESE150 Spring 2021 IDEA Ò Virtualize the processor É Make it look like we have multiple processors É With each program running on its own processor VIRTUALIZATION Ò “Own” processor É Can put data in memory where it wants É Doesn’t have to worry about another program scribbling over its memory É Its state is preserved and isolated É Looks like it runs all the time on the processor Ð Doesn’t need to be programmed to allow other programs to run 7 8 ESE150 Spring 2021 ESE150 Spring 2021 KEY IDEA MMEMORYEMORYSSAVEAVE/R/RESTOREESTORE Ò Can capture state of a processor É All the information that defines the current point in the computation É i.e. program counter, data and instruction memory Ò Can save that in memory É A different memory from what the process sees É (could be different range of addresses) Ò Fully represents the running program Ò Can restore that from memory to the processor Ò Can save/restore without affecting the functional behavior of the program 9 10 ESE150 Spring 2021 ESE150 Spring 2021 MMEMORYEMORYSSAVEAVE/R/RESTOREESTORE MEMORY SAVE/RESTORE Save 11 12 2 3/31/21 ESE150 Spring 2021 ESE150 Spring 2021 MEMORY SAVE/RESTORE MEMORY SAVE/RESTORE Restore Restore 13 14 ESE150 Spring 2021 ESE150 Spring 2021 SHARING PROCESSOR Ò Now that we can save/restore the state Ò Can share processor among processes Worksheet Exercise É (Restore state; run for time; save state) Ò Isolation: none of the processes need to know DEMONSTRATION about each other É Each thinks it has the a whole machine É Just need to restore/save state around epochs where the process gets to run on the processor 15 16 ESE150 Spring 2021 ESE150 Spring 2021 WORKSHEET: EXECUTION EXERCISE EXECUTION EXERCISE Ò We’re going to simulate the computer and Ò Google Doc – simulate A for 12 cycles watch the processor state 17 19 3 3/31/21 ESE150 Spring 2021 ESE150 Spring 2021 SIMULATE SWAPPING SIMULATE SWAPPING Ò Imagine we ran A for 6 cycles (and saved state) Ò Simulate B for 6 cycles Ò Swap and Run B for 6 cycles É Individually Ò Swap and Run A for next 6 cycles Ò What get? É What should we get? Ò Swap and Run B for next 6 cycles 20 21 ESE150 Spring 2021 ESE150 Spring 2021 SIMULATE SWAPPING SIMULATE SWAPPING Ò Swap in A+6 and Simulate for 6 cycles (to 12) Ò Swap in B+6 and Simulate for 6 cycles (to 12) É individually É individually Ò What get? Ò What get? 22 23 ESE150 Spring 2021 ESE150 Spring 2021 SIMULATE SWAPPING REVIEW: KEY IDEA Ò Can capture state of a processor Ò Imagine we ran A for 6 cycles (and saved state) É All the information that defines the current point in the Ò Swap and Run B for 6 cycles computation (PC, data and instruction mem) Ò Swap and Run A for next 6 cycles Ò Can save that in memory É A different memory from what the process sees É What should we get? É (could be different range of addresses) Ò Swap and Run B for next 6 cycles Ò Fully represents the running program Ò Can restore that from memory to the processor Ò Can save/restore without affecting the functional Behavior of the program Ò Time-share processor à pretend have unlimited number 24 25 4 3/31/21 ESE150 Spring 2021 ESE150 Spring 2021 IPOD PROCESSOR Ò Early based on PortalPlayer series MEDIA PROCESSORS É Two ARM7TDMI cores É 80MHz each Ò Guesses are ARM7 or ARM8 26 27 Penn ESE532 Fall 2020-- DeHon ESE150 Spring 2021 APPLE A13 BIONIC BIG IDEAS 2 Ò 98mm , 7nm Ò 8.5 Billion Tr. Ò Virtualize hardware Ò iPhone 11 + É Identify state; save/restore from memory Ò 6 ARM cores Ò Program view: owns complete machine É 2 fast (2.6GHz) Ò Allows programs to share limited physical É 4 low energy hardware (e.g. processor) Ò 4 custom GPUs É Provide illusion of unlimited hardware Ò Neural Engine Ò Operating System is the program that É 5 Trillion ops/s? manages this sharing 28 29 ESE150 Spring 2021 ESE150 Spring 2021 LEARN MORE REMINDERS Ò CIS380 – Operating Systems Ò Feedback Ò Lab9 due on Friday 30 31 5.