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n00b Kernel Hacker
- Ex-Intern @ NVIDIA Korea (Security System Software) (2024.06-2024.11)
- Ex-Intern @ Panmneisa (CXL emulation stuff) (~2023.12)
- Undergraduate majoring CSE (estimated graduation: Feb. 2025)
- Working as reviewer at Linux Slab subsystem
- Born in August 6, 2000

Opinions are my own.

My interests are:
Memory Management,
Computer Architecture,
Circuit Design,
Virtualization
Edited 1 year ago
Today I learned:

CXL memory can be mapped as 'System RAM' or 'Soft Reserved' by platform firmware. Or it can be dynamically provisioned by (since v6.3) CXL region driver.

And 'Soft Reserved' or dynamically provisioned CXL RAM region can be used in two ways:

1. Applications mmap() to /dev/daxX.Y files, just like traditional persistent memory devices.
2. Kernel use it as System RAM via dax_kmem driver.

And a weird fact is that when dax_kmem onlines CXL (and other performance-differentiated like pmem) memory, to ZONE_NORMAL, not ZONE_MOVABLE.
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@lkundrak @bagder

for a moment
was wondering whose face it is
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Working on a series for 6.8 probably...
So far...
26 files changed, 39 insertions(+), 4375 deletions(-)
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@djlink

looks like a horror movie poster lol
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@ljs oh no, take care!
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Edited 1 year ago
Booting the latest kernel is always fun ;)

I was hit by BUG_ON() because I enabled CONFIG_DEBUG_VIRTUAL=y.
It made my machine crash and I wrote and sent a quick hack to fix this.

https://lore.kernel.org/lkml/CAB=+i9QiJ=BXkQuCFJTh3dMXrkKQvVA2EM51Mj6SsDMimWQ71g@mail.gmail.com

Today I learned:

- Better to use proper tags for regzbot next time I report something, don't make @kernellogger do that instead of me.

- __init and __exit are compiler attributes that makes functions to be in specific ELF sections (.init.text and .exit.text), to drop portions of unused kernel code.

- When a kernel feature is built into kernel rather than built as a module, functions marked __init are dropped after initialization and functions marked __exit are dropped and never used. because you can't unload a built-in kernel feature ;)

- Some architectures drop .exit.text section at link time, but some drop at runtime. this is due to complexity of link-time reference counting between functions (? which I have no idea yet)

- On architectures that drop it at runtime, functions marked __exit are dropped in free_initmem() because .exit.text section is between __init_begin and __init_end.

- I need an automatic bisection system to save time in the future.

One piece of information I'm missing here is why it did not crash before the commit :(
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Edited 1 year ago
@ljs @thomy2000 Can I put both of books in my bag please?

Oh, I need much bigger bag...
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2/…patches from new or rare contributors should have some kind of tag to indicate things like

(1) I have no interest in learning how to do things better, I just want it fixed; I'm thus happy if someone dramatically changes the patch or writes a better one.

(2) I'd really like to learn how to do this properly, hence would be grateful if someone could guide me somewhat.

Why? Well, misunderstandings here can be annoying and a waste of time for both sides (and lead to situations like the above).

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Thorsten Leemhuis (acct. 1/4)

"[…] Instead of accepting my [] patch or guiding me towards a better solution, he went ahead and implemented his own fix, giving me credit only for reporting the issue […]

My first contribution to the [] was a really frustrating and discouraging experience, dealing with people who do not think it’s important to get proper recognition for your work. […]"

https://ariel-miculas.github.io/How-I-got-robbed-of-my-first-kernel-contribution/

1/ Side note: I sometimes wonder if…

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@ljs @sj I appreciate it
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@ljs @sj more holidays to you means more pages written?
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Edited 1 year ago
My android phone kills the chrome app very often. It is painful that I can't see system logs. I suspect it was the OOM killer that kills it.
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nice 6 days break for Chuseok! (korean thanksgiving day)
@sj 즐거운 추석 되세요 :)
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@ptesarik nope ;) some DNS hostimg services provide updating records via web APIs!
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@vbabka because a memory leak is common?
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@vbabka btw how do you think about maintaining a slab/experimental branch so that it can be tested first even before being reviewed and went to slab/for-next?
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Welcome to the cycle of generative AI making search worse.

Quora uses ChatGPT which hallucinates an answer to a nonsense question.

Google Search picks up this nonsense answer from Quora which has high page rank and treats it as an instant answer.

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