Operating Systems 2021F Lecture 20

Video

Video from the lecture given on November 30, 2021 is now available:

• video
• auto-generated captions

Video is also available through Brightspace (Resources->Class zoom meetings->Cloud Recordings tab)

Notes

Lecture 20
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 - for A3Q6, if you reported the results of a reasonable experiment
   you can get full credit even if you got the wrong answer

"Holes" in UNIX files
 - why allocate blocks that are storing all 0's (null bytes)?
 - If you write zeros to a file, it will take up space
 - however, if you seek past the end of a file and then write,
   the space in between will become a "hole" which logically has
   null bytes but takes up no space on disk

in the Linux kernel, processes and kernel threads are represented
as "tasks"
  - something that can be scheduled to run on the CPU

If you want to do something in kernel space that you know how to do from userspace using system calls
 - look at how the system call is implemented