Hyeonggon Yoo
Posts
469Following
90Followers
94- Intern @ NVIDIA Korea (Security System Software) (2024.06 ~)
- 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
Hyeonggon Yoo
hyeyoo
Edited 1 year ago
When there are no free pages in free list of the requested order, buddy allocator splits a larger page into smaller ones, and allocates a one of the split pages.
TIL: The way buddy splits large pages (and allocating first or last part of a large page) during the expand() function significantly impacts the mergability of the scatter-gather list for IO. The likeliness that pages are allocated in PFN order is important for mergability. This is so subtle and I didn't realize this :(
Consider a scenario where there is only an order 2 block, and four order 0 requests are served. In the diagram above, they are allocated in PFN order, while in the other diagram, they are allocated in the reverse order.
https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=c75b81a5da09be94099cf7b46bdb32fedc8ce71a
And in the history this thing has introduced a regression because the order was not preserved (by mistake) when pages are allocated from PCP lists with __GFP_COLD ;)
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e084b2d95e48b31aa45f9c49ffc6cdae8bdb21d4
TIL: The way buddy splits large pages (and allocating first or last part of a large page) during the expand() function significantly impacts the mergability of the scatter-gather list for IO. The likeliness that pages are allocated in PFN order is important for mergability. This is so subtle and I didn't realize this :(
Consider a scenario where there is only an order 2 block, and four order 0 requests are served. In the diagram above, they are allocated in PFN order, while in the other diagram, they are allocated in the reverse order.
https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=c75b81a5da09be94099cf7b46bdb32fedc8ce71a
And in the history this thing has introduced a regression because the order was not preserved (by mistake) when pages are allocated from PCP lists with __GFP_COLD ;)
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e084b2d95e48b31aa45f9c49ffc6cdae8bdb21d4
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Hyeonggon Yoo
hyeyoo
Edited 1 year ago
I've just built my first 2 socket server (36C/72T, DDR4 256GB ECC/REG RAM) for experimenting with NUMA.
It's an old xeon server (Broadwell), but enough to play with!
It's an old xeon server (Broadwell), but enough to play with!
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Hyeonggon Yoo
hyeyoo
Edited 1 year 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?
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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Hyeonggon Yoo
hyeyoo
I want NVIDIA's proprietary GPU drivers 🥲
nouveau does not support virtual GPUs...
nouveau does not support virtual GPUs...
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Hyeonggon Yoo
hyeyoo
Edited 1 year 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.
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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