COMP 3430 – Operating Systems
Segmentation part 3
April 8th, 2022
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By the end of today’s lecture, you should be able to:
▶ Catch a segmentation fault (maybe).
▶ Compare and contrast free space
management policies.
▶ Describe general strategies related to free
space management.
The Woggle-Bug Book (Public Domain)
Can we catch SIGSEGV?
Let’s write/look at some code.
wat. (Pixabay License)
Segmentation in action
Let’s draw out what’s happening with segmentation and identify some new problems.
Heap allocators
Here are some heap allocators:
1. jemalloc 2. mimalloc 3. glibcmalloc
That’s a heap. (Pixabay License)
For each of these heap allocators, try to determine which strategy the allocator uses:
▶ Best fit ▶ Worst fit ▶ First fit ▶ Next fit
One fish two fish red fish blue fish (©Random House, Fair use)
Why not the kernel?
Why not discuss free-space management and segmentation from the perspective of the Linux kernel?
Tux! (©gg3po, , , GPL)
Let’s take a look at the course schedule.
▶ You can “catch” segmentation faults.
▶ Memory allocators use different strategies for managing free
▶ Sometimes multiple strategies.
▶ Segmentation is an architecture-specific VM feature. ▶ Not generally used.
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