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A relatively new professional kernel hacker, born in August 6, 2000, and living in Korea (South!).

- Linux Kernel Developer @ Oracle (Linux Kernel MM) (2025.02 ~ Present)
- Reviewer for the Linux Slab & Reverse Mapping subsystem
- Former Intern @ NVIDIA, SK Hynix, Panmnesia (Security, MM and CXL)
- B.Sc. in Computer Science & Engineering, Chungnam National University (Class of 2025)

Opinions are my own.

My interests are:
Memory Management,
Computer Architecture,
Circuit Design,
Virtualization

Harry (Hyeonggon) Yoo

Edited 3 months ago
How does the kernel manage LRU lists and perform memory reclaim when memory cgroup feature is enabled? I wrote an article to answer that question.

Memory Cgroup Naturalization in the Linux Kernel v3.3
https://vmscan.org/memory-cgroup-naturalization-in-the-linux-kernel-v33

In the early days, memory cgroup was “bolted onto” the memory management subsystem, using a double-LRU scheme: each page was linked to both global and per-memcg lists—leading to a moderate memory overhead and complicating reclaim logic.

Linux v3.3 changed that. Memory cgroups were fully integrated into the MM core, global LRU lists were removed on memcg-enabled systems, and global reclaim began walking memcg hierarchy and scanning the per-memcg LRU lists, scanning each group in proportion to its memory usage.

This reduced memory overhead and simplified the reclaim code. More details in the article!
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Linux 6.15 Released With Continued Rust Integration, Bcachefs Stabilizing

As anticipated the Linux 6.15 kernel is out today in stable form. Linux 6.15 brings a lot of new hardware support, security improvements, various other kernel innovations, and more...
https://www.phoronix.com/news/Linux-6.15-Released

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i hope the nvidia driver doesn't crash

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AGRO TURBO.EXE SATAN 🇺🇦🇨🇿

then: "when I grow up I'll be programming computers"
now: "i vibepirated code i wrote"

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Harry (Hyeonggon) Yoo

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Harry (Hyeonggon) Yoo

Edited 4 months ago
Recently started learning how memory cgroup in the Linux kernel works, so started writing articles about it. The first posting for my English blog vmscan.org!

A brief look at memory cgroup controller introduced in the Linux kernel v2.6.25.
https://vmscan.org/a-brief-look-at-memory-cgroup-controller-introduced-in-linux-kernel-v2625
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Harry (Hyeonggon) Yoo

Edited 4 months ago
I have been spending seven hours every Saturday studying the Linux kernel with a study group for years. It's been fun, but over time, I started to feel like I wasn’t spending my time wisely. I have to accept the fact that I don’t have enough time to regularly look at anything outside of MM.
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Harry (Hyeonggon) Yoo

Edited 4 months ago
I tried GPT-o3 (which uses 'advanced reasoning') to review slab patches to see if it works, and it generated many false comments. :P Less advanced than I expected.
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Spot on advice for any field.

For gym motivation is useless, it's all discipline, your test is on a day when you 100% hate it and want to do ANYTHING ELSE.

Music is my hobby but barely done any, because it is work really, a different kind, but if you want to get anywhere with it, you have to have the same discipline.

But I plan to apply the same gym-like discipline to that to get what I want out of it.

And of course this goes for kernel work too, obviously.

https://www.youtube.com/watch?v=4pw1tmGh3dk

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Harry (Hyeonggon) Yoo

Edited 4 months ago
Blogging time after a long time.
/me again realizes that things not documented are quickly reclaimed from memory.
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Harry (Hyeonggon) Yoo

Edited 6 months ago
Oh, I didn't know a CVE can be assigned to my bug fix without me requesting or realizing it. I thought (despite not being a security expert) it was not a 'fun' bug to exploit for attackers.

https://nvd.nist.gov/vuln/detail/CVE-2025-21860
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Vlastimil Babka 🇨🇿🇪🇺🇺🇦

Well well, look what the cat dragged in
https://nostarch.com/linux-memory-manager

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Very happy to announce my book The Linux Memory Manager is now available to pre-order at

https://nostarch.com/linux-memory-manager

It's a comprehensive 1,300 page exploration of how memory functions in Linux that goes into great depth on the subject, and is the first book of its kind for 20 years :)

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Harry (Hyeonggon) Yoo

Edited 7 months ago
This book serves as a guiding light in navigating the increasingly complex memory management subsystem. A must-have book if you're interested in memory management!

I'mq glad to see the author's long effort finally paying off. Finally available for preorder 👏.

Already ordered one!

https://fosstodon.org/@ljs/114004492112728241
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Jonathan Corbet

Forbes is warning us that Android phones are under severe risk due to a kernel vulnerability:

https://www.forbes.com/sites/zakdoffman/2025/02/03/google-warns-all-android-users-your-phone-is-now-at-risk/

This comes from Google's Android security bulletin for February:

https://source.android.com/docs/security/bulletin/2025-02-01

...which informs us that "There are indications that CVE-2024-53104 may be under limited, targeted exploitation". The vulnerability in question, though, is CVE-2024-53104:

https://lwn.net/ml/all/2024120232-CVE-2024-53104-d781@gregkh

...which is in the uvcvideo camera driver. Either I'm missing something badly, or the only way to exploit this would be to plug a malicious camera device into the phone. I can see why they would want to fix this, but I'm not sure it's a red-alert situation for most of us?
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Nafnlaus 🇮🇸 🇺🇦

Pretty much every serious photographer here tries to capture photos of the and the together. Sometimes, they succeed quite well ;) Photos from Wioleta Gorecka, taken near Reykjanesvíti.

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Intel SNC6 Sub-NUMA Clustering Support With Linux 6.13

A few weeks back I wrote about Intel engineers preparing SNC6 support with Linux for six nodes per L3 cache. That was the first time hearing of SNC6 with SNC 1/2/3/4 sub-NUMA clustering modes being more common. That support is now ready for merging with the Linux 6.13 kernel cycle...
https://www.phoronix.com/news/Intel-SNC6-For-Linux-6.13

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