Operating Systems 2017F Lecture 17 - Revision history

HebaJallad: /* In Class */

2017-11-16T20:39:44Z

In Class

@@ Line 30: / Line 30: @@
    - Realize that the assumptions behind code you find don't necessarily match
      your own.
 * Understand the "flow of control" inside the program

2017-11-15T03:19:14Z

Additional Notes

← Older revision		Revision as of 03:19, 15 November 2017
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	<br>		<br>
	Memory overcommitment<br>		Memory overcommitment<br>
	Memory does not get allocated when you mmap. It is loaded "lazily" ~~int he~~ Linux kernel. It is possible to allocate way more memory than can ever be used. <br>		Memory does not get allocated when you mmap. It is loaded "lazily" in the Linux kernel. It is possible to allocate way more memory than can ever be used. <br>
	Goes into "memory debt" <br>		Goes into "memory debt" <br>

2017-11-15T03:14:24Z

Midterm Review

← Older revision		Revision as of 03:14, 15 November 2017
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	===Midterm Review===		===Midterm Review===
	1. Execve and no it does not create a new process		1. Execve and no it does not create a new process

			2. Dynamically linked programs map in dynamically linked libraries

	3. Hard links maps filenames to inodes		3. Hard links maps filenames to inodes

2017-11-14T21:16:17Z

Additional Notes

← Older revision		Revision as of 21:16, 14 November 2017
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	<br>		<br>
	Check for errors ALWAYS or they will cascade and hurt you later<br>		Check for errors ALWAYS or they will cascade and hurt you later<br>
	This will save you from later errors<br>		*This will save you from later errors<br>
	Kernel has to live cleanly<br>		*Kernel has to live cleanly<br>
			*This principle applies to any large scale coding
	<br>		<br>
	Find another part of the kernel that is close to what you want to do (Search online! This is a good link: http://elixir.free-electrons.com/linux/v4.4.83/source <br>		Find another part of the kernel that is close to what you want to do (Search online! This is a good link: http://elixir.free-electrons.com/linux/v4.4.83/source <br>
	You do not understand all abstractions and assumptions, so "pattern match" to minimize trouble <br>		You do not understand all abstractions and assumptions, so "pattern match" to minimize trouble <br>
			*Functionality that you want to implement might already exist in the kernel, look at how they do things and follow the pattern.<br>
			*Refine understanding as you go, the other implementation might be for something else. <br>
	<br>		<br>
	Realize that the assumptions behind code you don't necessarily match to your own. Spend the time reading other people's code. <br>		Realize that the assumptions behind code you don't necessarily match to your own. Spend the time reading other people's code. <br>

2017-11-14T20:56:11Z

Video

← Older revision		Revision as of 20:56, 14 November 2017
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	==Video==		==Video==

			The video from the lecture given on Nov. 14, 2017 [http://homeostasis.scs.carleton.ca/~soma/os-2017f/lectures/comp3000-2017f-lec17-14Nov2017.mp4 is now available].

	==Notes==		==Notes==

2017-11-14T20:55:05Z

@@ Line 1: / Line 1: @@
 == Midterm Review ==
 . Execve and no it does not create a new process
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 * also, int sem parameter isn't a ptr so it's a local variable.
-== Additional Notes ==
+===Additional Notes===
 How do you do kernel hacking? Some tips for low level kernel code:

2017-11-14T20:10:10Z

Midterm Review

← Older revision		Revision as of 20:10, 14 November 2017
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	== Midterm Review ==		== Midterm Review ==
	1. Execve and no it does not create a new process		1. Execve and no it does not create a new process

			3. Hard links maps filenames to inodes

			4. Sleep until the consumer wakes it

			5. Using type conversion, read returns number of bytes written. We must convert back to the number of unsigned long, minus one because maximum index of array is one less

	6. uses of signals:		6. uses of signals:

2017-11-14T20:07:59Z

Additional Notes

← Older revision		Revision as of 20:07, 14 November 2017
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	What criteria should the scheduler use in deciding what to run?<br>		What criteria should the scheduler use in deciding what to run?<br>
	*Fairness: Starvation is when a program does not get the CPU <br>		*Fairness: Starvation is when a program does not get the CPU <br>
			**Everyone should get a turn
			**CPU is passed around
			** Nobody should be left that they never get the CPU
	**Prevent Starvation <br>		**Prevent Starvation <br>
	**Absent other conditions, equal allocation of resources		**Absent other conditions, equal allocation of resources

2017-11-14T19:24:01Z

Additional Notes

← Older revision		Revision as of 19:24, 14 November 2017
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	**never Biased enough		**never Biased enough
	**always hacks, heuristics		**always hacks, heuristics
			<br>
			Memory overcommitment<br>
			Memory does not get allocated when you mmap. It is loaded "lazily" int he Linux kernel. It is possible to allocate way more memory than can ever be used. <br>
			Goes into "memory debt" <br>

2017-11-14T19:20:06Z

Additional Notes

← Older revision		Revision as of 19:20, 14 November 2017
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	*Bias resources towards "foreground" tasks in interactive systems		*Bias resources towards "foreground" tasks in interactive systems
	**never Biased enough		**never Biased enough
			**always hacks, heuristics