Operating Systems Spring 2003 Ittai Abraham Zinovi Rabinovich The School of Computer Science and Engineering The Hebrew University of Jerusalem Operating Systems – p.1
Course Information Lecturer: Gregory (Grisha) Chockler (grishac@cs.huji.ac.il) Teaching Assistants Ittai Abraham, ittaia@cs.huji.ac.il Zinovi Rabinovich, nomad@cs.huji.ac.il URL: http://www.cs.huji.ac.il/ ˜ os Newsgroups: Moderated: local.course.os.ta Non-moderated: local.course.os.st Operating Systems – p.2
Administration and Rules All regulations and requirements are clearly stated in the course homepage. In case of differences - the homepage version is compelling There are 6 exercises: 3 programming + 3 theoretical Your grade will be based on 5 best Programming exercises can be done in pairs (but not in larger groups) Exercises are 40% of the grade OS: Linux Language: C, C++, English Operating Systems – p.3
Administration and Rules Late submissions: 3 points one day 6 points for two days later submissions are not allowed All exercises have an automatic 3 point bonus Irurim: bonus is automatically lost no later then 2 weeks from the date the grades have been given Operating Systems – p.4
Administration and Rules Miluim: Up to 10 days no changes More then 10 days excuse one exercise (but not for the partner that remains) If there are two partners from different pairs where in every pair on e partner is in miluim, the pairs may merge The TA must be notifies in advance about miluim period (os@cs.huji.ac.il only) Operating Systems – p.5
Administration and Rules Submission: tar file containing the README, source files, make files see the detailed instructions on the exercise page tar cvf exN.tar <files> submit the tar file using browser submit theoretical exercise using the course mailbox keep your own version of the exercise Operating Systems – p.6
Collaboration We encourage you to collaborate on homework. However: You must write up solutions on your own You may not look at or copy other people solutions You may not provide solutions to be copied. Neither by allowing access nor by creating a commonly accessed copy of your solution If you do collaborate on homework, you must cite, in your written solution, all of your collaborators. If you use sources beyond the course materials in one of your solutions, be sure to include a proper scholarly citation of the source. Operating Systems – p.7
Bibliography Maurice J. Bach, The design of the UNIX Operating System Richard W. Stevens, Advanced Programming in the UNIX Environment Samuel J. Leffer et. al., The Design and Implementation of the 4.3 BSD OS Raj Jain, The art of computer system performance analysis Operating Systems – p.8
I never saw a wild thing sorry for itself. A bird will fall frozen dead from a bough without ever having felt sorry for itself. Operating Systems – p.9
Computer System Structures Interrupts DMA Memory Hierarchy Operating Systems – p.10
General Structure printer D2 D1 disk printer CPU controller controller system bus memory controller memory Operating Systems – p.11
Interrupts Interrupts are signals about events Operating Systems – p.12
Interrupts Interrupts are signals about events Triggered by hardware Operating Systems – p.12
Interrupts Interrupts are signals about events Triggered by hardware Division by zero Operating Systems – p.12
Interrupts Interrupts are signals about events Triggered by hardware Division by zero Keyboard input Operating Systems – p.12
Interrupts Interrupts are signals about events Triggered by hardware Division by zero Keyboard input Disc completed writing a requested block Operating Systems – p.12
Interrupts Interrupts are signals about events Triggered by hardware Division by zero Keyboard input Disc completed writing a requested block Each interrupt has a ’service routine’ responsible for dealing with the event Operating Systems – p.12
Interrupt Handling I Interrupts are handled using the following sequence CPU is interrupted - stop whatever it does and.. Operating Systems – p.13
Interrupt Handling I Interrupts are handled using the following sequence CPU is interrupted - stop whatever it does and.. ...find where service routine is and... Operating Systems – p.13
Interrupt Handling I Interrupts are handled using the following sequence CPU is interrupted - stop whatever it does and.. ...find where service routine is and... ...execute service routine.. Operating Systems – p.13
Interrupt Handling I Interrupts are handled using the following sequence CPU is interrupted - stop whatever it does and.. ...find where service routine is and... ...execute service routine.. .. go back to whatever you did Operating Systems – p.13
Interrupt Handling II How do we find where service routine is? Operating Systems – p.14
Interrupt Handling II How do we find where service routine is? There is a predefined number of interrupts - use table of pointers (to functions) Operating Systems – p.14
Interrupt Handling II How do we find where service routine is? There is a predefined number of interrupts - use table of pointers (to functions) But where is the table? Operating Systems – p.14
Interrupt Handling II How do we find where service routine is? There is a predefined number of interrupts - use table of pointers (to functions) But where is the table? Interrupt array starts at a predefined address in low memory (100 first locations) Operating Systems – p.14
Interrupt Handling II How do we find where service routine is? There is a predefined number of interrupts - use table of pointers (to functions) But where is the table? Interrupt array starts at a predefined address in low memory (100 first locations) How do we know which table entry corresponds to a given interrupt? Operating Systems – p.14
Interrupt Handling II How do we find where service routine is? There is a predefined number of interrupts - use table of pointers (to functions) But where is the table? Interrupt array starts at a predefined address in low memory (100 first locations) How do we know which table entry corresponds to a given interrupt? Interrupt array is indexed by a unique device number Operating Systems – p.14
Interrupt Handling II How do we find where service routine is? There is a predefined number of interrupts - use table of pointers (to functions) But where is the table? Interrupt array starts at a predefined address in low memory (100 first locations) How do we know which table entry corresponds to a given interrupt? Interrupt array is indexed by a unique device number The number is assigned when the device is registered (asks for interrupt assignment) Operating Systems – p.14
Interrupt Handling III How do we know where to go back to? Operating Systems – p.15
Interrupt Handling III How do we know where to go back to? Keep ’a bookmark’ of where you stooped - use regular nested stack Operating Systems – p.15
Interrupt Handling III How do we know where to go back to? Keep ’a bookmark’ of where you stooped - use regular nested stack We stop whatever we do to handle an interrupt. Even a service routine? Operating Systems – p.15
Interrupt Handling III How do we know where to go back to? Keep ’a bookmark’ of where you stooped - use regular nested stack We stop whatever we do to handle an interrupt. Even a service routine? Not always. Usually interrupts are disabled during a service routine execution. Operating Systems – p.15
Interrupt Handling III How do we know where to go back to? Keep ’a bookmark’ of where you stooped - use regular nested stack We stop whatever we do to handle an interrupt. Even a service routine? Not always. Usually interrupts are disabled during a service routine execution. Computer architecture exist that allow nested interrupt handling. Operating Systems – p.15
Interrupt Handling III How do we know where to go back to? Keep ’a bookmark’ of where you stooped - use regular nested stack We stop whatever we do to handle an interrupt. Even a service routine? Not always. Usually interrupts are disabled during a service routine execution. Computer architecture exist that allow nested interrupt handling. These architectures usually use a priority scheme - interrupts with higher priority can break a servicing routine of a lower priority interrupts. Operating Systems – p.15
DMA - Direct Memory Access DMA is just another controller Operating Systems – p.16
DMA - Direct Memory Access DMA is just another controller DMA receives address of a buffer in memory and address of a block on disk from CPU Operating Systems – p.16
DMA - Direct Memory Access DMA is just another controller DMA receives address of a buffer in memory and address of a block on disk from CPU DMA runs the interaction between the disk and memory to transfer the required information Operating Systems – p.16
DMA - Direct Memory Access DMA is just another controller DMA receives address of a buffer in memory and address of a block on disk from CPU DMA runs the interaction between the disk and memory to transfer the required information It then interrupts CPU to inform about the operation completion Operating Systems – p.16
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