Hyeonggon Yoo
Posts
474Following
89Followers
94- 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
@ljs @ptesarik @vbabka
CXL is not feasible for unmovable kernel allocations regardless of latency if the goal is reduction in total memory cost (and thus dynamic capacity change mechanism is used)
BTW the latency is not that bad, it's just like a far and far NUMA node...
ofc emulated CXL is a complete beast - someone recently reported having 500KB/s bandwidth with it ;)
CXL is not feasible for unmovable kernel allocations regardless of latency if the goal is reduction in total memory cost (and thus dynamic capacity change mechanism is used)
BTW the latency is not that bad, it's just like a far and far NUMA node...
ofc emulated CXL is a complete beast - someone recently reported having 500KB/s bandwidth with it ;)
1
0
0
Hyeonggon Yoo
hyeyoo
Edited 1 year ago
I need to learn Ansible instead of writing non-portable scripts and memorizing all of them
0
0
1
Oh, tuxmake provides repeatable builds and building in docker containers.
It would be nice solution for parallel GCOV builds
https://tuxmake.org
It would be nice solution for parallel GCOV builds
https://tuxmake.org
0
0
0
1
0
2
Hyeonggon Yoo
repeated
repeated
A LKML thread meme summary, pure shitposting because SCNR, not meant as an endorsement nor ridicule of any side
Show content
STOP DOING MSEAL()
SYSCALLS WERE NOT SUPPOSED TO BE GIVEN MM_SEAL_ FLAGS
YEARS OF MINMUTABLE() yet NO REAL-WORLD USE FOUND for using more than addr, len PARAMETERS
Wanted not to bother with that anyway to get a break? We had a tool for that: It was called "LD.SO"
"one place honors the sealing, random other places do not" - Statements dreamed up by the utterly Deranged.
LOOK at what Chrome has been demanding your Support for all this time, with all the mprotect(2) permission reduction & OPENBSD_MUTABLE we built for them.
(This is REAL Code, done by REAL Kernel developers).
ON_BEHALF_OF_KERNEL ?????
ON_BEHALF_OF_USERSPACE ???????
VM_SEAL_* -> MM_SEAL_* -> MM_ACTION_* ?????????????????
"Hello, I would like a MM_SEAL_MUNMAP but not MM_SEAL_MMAP VMA please."
They have played us for absolute fools
SYSCALLS WERE NOT SUPPOSED TO BE GIVEN MM_SEAL_ FLAGS
YEARS OF MINMUTABLE() yet NO REAL-WORLD USE FOUND for using more than addr, len PARAMETERS
Wanted not to bother with that anyway to get a break? We had a tool for that: It was called "LD.SO"
"one place honors the sealing, random other places do not" - Statements dreamed up by the utterly Deranged.
LOOK at what Chrome has been demanding your Support for all this time, with all the mprotect(2) permission reduction & OPENBSD_MUTABLE we built for them.
(This is REAL Code, done by REAL Kernel developers).
ON_BEHALF_OF_KERNEL ?????
ON_BEHALF_OF_USERSPACE ???????
VM_SEAL_* -> MM_SEAL_* -> MM_ACTION_* ?????????????????
"Hello, I would like a MM_SEAL_MUNMAP but not MM_SEAL_MMAP VMA please."
They have played us for absolute fools
3
8
21
Hyeonggon Yoo
hyeyoo
Edited 1 year ago
This is how a silently enabled kernel configuration can affect your system performance:
https://lore.kernel.org/stable/97397e8d-f447-4cf7-84a1-070989d0a7fd@amazon.com/T/#u
I fixed this at the beginning of this year, but did not backport to stable trees. Luiz Capitulino from Amazon reported that this resulted in performance regression in their 6.1 kernels.
DEBUG_PREEMPT has been enabled by default since pre-git era for PREEMPT kernels, but distros that were using PREEMPT_VOLUNTARY silently enabled PREEMPTION and DEBUG_PREEMPT after the introduction of PREEMPT_DYNAMIC. And DEBUG_PREEMPT is better disabled for production kernels regardless of the preemption model used.
https://lore.kernel.org/stable/97397e8d-f447-4cf7-84a1-070989d0a7fd@amazon.com/T/#u
I fixed this at the beginning of this year, but did not backport to stable trees. Luiz Capitulino from Amazon reported that this resulted in performance regression in their 6.1 kernels.
DEBUG_PREEMPT has been enabled by default since pre-git era for PREEMPT kernels, but distros that were using PREEMPT_VOLUNTARY silently enabled PREEMPTION and DEBUG_PREEMPT after the introduction of PREEMPT_DYNAMIC. And DEBUG_PREEMPT is better disabled for production kernels regardless of the preemption model used.
0
6
8
Hyeonggon Yoo
hyeyoo
Why are gcov/lcov/genhtml so sensitive to source code path :(
lcov/genhtml requires that there should be source code in the exactly same path of source code in the build machine.
lcov/genhtml requires that there should be source code in the exactly same path of source code in the build machine.
1
0
0
@chrisg haha yeah probably, but I think they need to learn how to find the right person to talk with.
1
0
1
Hyeonggon Yoo
hyeyoo
Errr.... IDK why people contact me via Linkedin asking 'Is your company willing to by hardware from us?'
I DON'T KNOW I AM AN INTERN :(
I DON'T KNOW I AM AN INTERN :(
2
0
2
Hyeonggon Yoo
hyeyoo
Edited 1 year ago
https://it.chosun.com/news/articleView.html?idxno=2023092102422
...Linux for Desktop opens new world...
...New opportunity for Korean OS in goverment PCs...
https://www.hancom.com/product/productGooroomMain.do
...Goorm OS provides secure, convenient, unique experience to desktop users...
...Goorm OS is based on debian linux...
Seriously?
I'm tired of fancy new Korea's OS platforms (K-OS) which is either 1) just another Linux distribution or 2) not Linux based but being so unusable
...Linux for Desktop opens new world...
...New opportunity for Korean OS in goverment PCs...
https://www.hancom.com/product/productGooroomMain.do
...Goorm OS provides secure, convenient, unique experience to desktop users...
...Goorm OS is based on debian linux...
Seriously?
I'm tired of fancy new Korea's OS platforms (K-OS) which is either 1) just another Linux distribution or 2) not Linux based but being so unusable
0
0
1
Hyeonggon Yoo
repeated
repeated
nixCraft 🐧
nixCraft@mastodon.social
Edited 1 year ago
Windows: 0
Linux: 1
It is not Linux's job to stop you from shooting your foot. If you so choose to do so, then it is Linux's job to deliver Mr. Bullet to Mr. Foot in the most efficient way it knows.
2
3
1
@lkundrak @liskin @monsieuricon @vbabka
(confession: I was torturing memory bus by fully cloning via virtio-fs (locally) instead of git.kernel{,testing}.org, before I learned how to do shallow clones and use reference git repositories)
(confession: I was torturing memory bus by fully cloning via virtio-fs (locally) instead of git.kernel{,testing}.org, before I learned how to do shallow clones and use reference git repositories)
1
0
2
1
0
1
2
0
1
Hyeonggon Yoo
hyeyoo
1
0
0
0
0
2