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"Compacting the Uncompactable" by Bobby Powers

46 videos recommended on HN
YouTube
3 HN users recommended this talk3 months2020–2025 score 3
Years with an HN recommendation, 2007–2026

Recommended as a great talk on solving fragmentation for C/C++ and runtimes like Ruby and Python without code changes.

Bobby Powers presents Mesh, a drop-in malloc replacement that eliminates memory fragmentation in unmodified C/C++ programs by compacting memory. The talk covers how it works despite C's fixed object addresses, and its benefits for programs like Redis.

“There was a great talk at Strange Loop about a drop-in malloc replacement which compacts.” (HN, 2022)

3 recommendations · 1 citations · Talks · advanced

4 Hacker News comments

From the HN archive; up to 20 kept per video, favoring different commenters. Recommendations first.

@remexre Dec 2020 Recommends
on HN thread How the Python object system works
There's an interesting talk [0] from Bobby Powers on how to make a malloc() and free() that perform compaction, to be able to release memory back to the operating system more frequently (and improve cache hit rates, etc.). But this isn't standard at all yet. [1]: [this video]
Talk on a malloc that compacts memory to return it to the OS.
@rtfeldman Jul 2022 Recommends
on HN thread Reference count, don't garbage collect
There was a great talk at Strange Loop about a drop-in malloc replacement which compacts. Apparently it actually led to memory usage improvements in industrial projects like Redis: [this video]
Drop-in compacting malloc replacement that improved memory use in projects like Redis.
@superjan Jan 2025 Recommends
on HN thread Using black magic to make a fast circular buffer (2017)
There’s a great paper from the group of Emery Berger, where they merge memory pages that become sparse. A kind of garbage collection for C and C++ languages. There’s also a good presentation about it on youtube. [link] The presentation: [this video]
Presentation on merging sparse memory pages, a kind of garbage collection for C/C++.

Citations, criticism and jokes

@ssokolow Jun 2022 Cites it
on HN thread Rust Is Hard, Or: The Misery of Mainstream Programming
> but malloc/free based systems also have a relatively high memory overhead due to fragmentation In case you haven't seen it, there's been some interesting progress on that front: [this video]
Shows progress on reducing fragmentation overhead in malloc/free systems.

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