Posts
535Following
101Followers
118- 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
repeated
Lorenzo Stoakes
ljs@mastodonapp.uk
A big issue in the kernel are asymmetries between review resource and patch submission.
If you have 20 inexperienced kernel engineers all doing big difficult work and submitting large series that need TONS of review (and sometimes essentially development-via-review) and only a few reviewers, you have a problem.
What compounds this is that not all review is equal.
It seems most people will only really look at the surface, and rather happily give tags.
I think that technical skill is not enough for review [as I have said very often - soft skills are the actually core ones] - you have to be willing to say no, you have to be willing to consider the wider picture.
Finding people who have the right skills, are willing to handle the stress + thanklessness, & who have the time is not easy.
So the asymmetry I think is insoluble.
It'd be good if we could have stricter controls to throttle incoming series though.
3
4
1
1
0
2
1
0
2
Thanks! I'm proud of how far I've come ;) just going to keep going.
my PT has successfully gaslighted me, like, 'getting lean is better than eating pizza and chicken" yeah sure sure
0
0
1
Harry (Hyeonggon) Yoo
hyeyoo- Five workout sessions per week (focusing on losing fat)
- Eating only 2 sandwiches per day (most of the time!)
Target weight is about 70-75kg... so still a long long way to go.
1
0
4
repeated
Marco Elver
melver@fosstodon.orgPrototype for type-based partitioning of Linux kernel slab caches: https://discourse.llvm.org/t/rfc-a-framework-for-allocator-partitioning-hints/87434/24?u=melver
Compiler seems to be doing a good-enough job of inferring allocated types per /proc/slabinfo. With the diagnostic -Rpass=alloc-token I can see about 965 allocation sites where it failed to infer the allocated type, but most of them are "bag of bytes", and only few with complex sizeof calculations like struct_size that are too opaque right now (but can be fixed).
2
3
1
Harry (Hyeonggon) Yoo
hyeyooWhen memory cgroup and memory allocation profiling are enabled (the former being very common in production and the latter less so), the kernel allocates two pointers per object: one for the memory cgroup to which it belongs, and another for the code location that requested the allocation.
In two special cases, this overhead can be eliminated by allocating slabobj_ext metadata from unused space within a slab page:
- Case 1. The "leftover" space after the last slab object is larger than the size of an array of slabobj_ext.
- Case 2. The per-object alignment padding is larger than sizeof(struct slabobj_ext).
Thanks to @vbabka who suggested an excellent general approach to cover Case 1 and 2 with a minimal performance impact on the memory cgroup charging code (more details in the cover letter)
For these two cases, one or two pointers can be saved per slab object. Examples include the ext4 inode cache (case 1) and the xfs inode cache (case 2). That results in approximately 0.7-0.8% (memcg) or 1.5-1.6% (memcg + mem profiling) of the total inode cache size.
https://lore.kernel.org/linux-mm/20250827113726.707801-1-harry.yoo@oracle.com/
0
1
2
Harry (Hyeonggon) Yoo
hyeyoo
0
0
2
repeated
Harry (Hyeonggon) Yoo
hyeyoo
0
0
1
