Posts
529
Following
99
Followers
116
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
hyeyoo

Harry (Hyeonggon) Yoo

Edited 2 years ago
started wondering where it's documented that x86 processors deal with the synonym problem, as they use VIPT data caches.

on ARMv8 processors there is an architectural guarantee that data caches acts as PIPT cache even if it's actually VIPT, so it's guaranteed not to suffer from D-cache aliasing.

I've been heard that there is a similar guarantee on x86 processors but haven't found any official references about it - errr, I guess it's time to read some part of the intel manual.

btw this is quite old but is very nice introduction:
https://www.linuxjournal.com/article/7105
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @ljs
@ljs @kernellogger @sj

LOL what
you mean /proc/sys/vm/drop_caches?
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @ljs
@ljs @kernellogger @sj

Ah, I added sj because IIRC he's planning implement an auto tuner for DAMON parameters - no one should be like "bpftune can tune everything and make more parameters"

it would have been horrible if i.e. active/inactive list balancing was implemented as a kernel parameter :P
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @ljs
@ljs @kernellogger @sj

That's a perspective I didn't have, and it makes sense. So, it's like performing CPR on this messed-up situation?
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to
Edited 2 years ago
@kernellogger

@sj you might be interested in adapting DAMON parameters?
btw I wonder how broad range of parameters could be covered
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to
@kernellogger WOW that is amazing work!
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @vbabka
Edited 2 years ago
@vbabka @ljs would running mm-stable make it stable again? 🥲 I didn't threw it away yet
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @ljs
@ljs please do the same to overgrown MM code
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to
@cwayne @ljs is it better than normal tablets (like ipad)?
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hyeyoo

Harry (Hyeonggon) Yoo

Edited 2 years ago
I bought a new graphics card yesterday, and it came with a freebie. now my machine hangs whenever I boot a kernel with lockdep enabled.

Here is the link to the issue I posted on GitLab: https://gitlab.freedesktop.org/drm/nouveau/-/issues/237

BTW does DRM folks prefer using GitLab or the mailing list?
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hyeyoo

Harry (Hyeonggon) Yoo

I want NVIDIA's proprietary GPU drivers 🥲
nouveau does not support virtual GPUs...
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hyeyoo

Harry (Hyeonggon) Yoo

Edited 2 years ago
I was refreshing my zsdesc patch series but encountered unrelated bug while testing (I bought new RAM so it must be software bug...)

Fortunately it was bisectable and I'm writing a report about it
Not sure if people will welcome an oops image instead of text format.
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hyeyoo

Harry (Hyeonggon) Yoo

a funny thing about memtest is that it can fail due to memory failure.
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @hyeyoo
@ljs gotcha!
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @hyeyoo
@ljs hmm I tried to boot using two different bootable USBs but both says something has been corrupted. It makes me think the kernel may be innocent
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @ljs
@ljs directly on host, it was wild memory access according to KASAN.
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @ljs
Edited 2 years ago
@ljs sometimes during kernel compilation, sometimes while shutting down the machine for rebooting...
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hyeyoo

Harry (Hyeonggon) Yoo

Reply to @vbabka
@vbabka thanks, finally the semester is over!
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hyeyoo

Harry (Hyeonggon) Yoo

Edited 2 years ago
today I was hit by a kernel bug on the latest mm-unstable and so I was debugging it. but after a few kernel crashes even a normal kernel doesn't boot.... what's wrong with you :(

Not sure if it is a filesystem corruption caused by kernel bug, or they just did happen independently.
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hyeyoo

Harry (Hyeonggon) Yoo

Edited 2 years ago
I have the last final exam today. haven't decided what to do during the summer vacation yet, but it will mostly involve learning new things and writing some kernel code.
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