Hyeonggon Yoo
Posts
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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
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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@vbabka @AnnaPlusPlus
Sent risky patches that maintainers would not welcome
.....guess I'd better send more
Sent risky patches that maintainers would not welcome
.....guess I'd better send more
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Hyeonggon Yoo
repeated
repeated
sj
sj
Edited 1 year ago
DAMON user-space tool (damo) has released[1] its 100th version. A mail[2] for the news, release stats, and appreciation to the DAMON community has also posted. From the mail:
"Looking forward to 200th, and 1,000th release of damo :D We, the community,
will make it together."
[1] https://github.com/awslabs/damo/releases/tag/v1.9.3
[2] https://lore.kernel.org/damon/20230807202044.98700-1-sj@kernel.org/
#linux #kernel #damon #damo
"Looking forward to 200th, and 1,000th release of damo :D We, the community,
will make it together."
[1] https://github.com/awslabs/damo/releases/tag/v1.9.3
[2] https://lore.kernel.org/damon/20230807202044.98700-1-sj@kernel.org/
#linux #kernel #damon #damo
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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
Sometimes my schedule goes out of control, and I find myself buried in the work I started. It can be overwhelming, and this is one of those moments.
However, there is some good news: it's likely that I will be participating in a field exercise program next semester at a startup that designs CXL devices.
It's a very nice opportunity, but at the same time, it's a pity that I'll be missing some classes!
However, there is some good news: it's likely that I will be participating in a field exercise program next semester at a startup that designs CXL devices.
It's a very nice opportunity, but at the same time, it's a pity that I'll be missing some classes!
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