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Kernel Articles, Mostly LWN
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Presentation: Opening the Box: Diagnosing Operating-System Task-Scheduler Behavior on Highly Multicore Machines
Julia Lawall discusses methods for diagnosing operating system task scheduler behavior on highly multicore machines, crucial for performance analysis. She explains the challenges of understanding kernel-level scheduling decisions and shares custom-built tooling for visualizing and analyzing scheduler traces to identify and resolve performance regressions. Gain deep insights into OS behavior.
By Julia Lawall -
The rest of the 6.15 merge window
Linus Torvalds released 6.15-rc1 and closed the 6.15 merge window on April 6. By that time, 12,633 non-merge changesets had found their way into his repository; that is substantially more than were merged during the entire 6.14 development cycle. Just under 6,000 of those changesets were merged after the first-half merge-window summary was written.
- The future of ZONE_DEVICE: some thoughts on how to bring an "ugly stepchild" of the memory-management subsystem a bit closer to the fold.
- Supporting untorn buffered writes: untorn (or atomic) writes are now supported in the kernel for direct I/O, should that support be extended to buffered I/O?
- An update on torn-write protection: changes and plans for untorn direct I/O writes for XFS and other filesystems.
- Better hugetlb page-table walking: a discussion on making hugetlb look a bit more like the rest of the memory-management subsystem.
- Page allocation for address-space isolation: unmapping sensitive kernel data whenever possible has the potential to increase security, but it will place some interesting demands on the memory-management subsystem.
- The future of guest_memfd: protecting guest pages from the host can be a difficult business.
- Three ways to rework the swap subsystem: swapping in Linux is a complex business; three sessions look at ways to both simplify the swap subsystem and make it more effective.
- Per-CPU memory for user space: per-CPU variables are an effective performance optimization in the kernel; how can similar benefits be brought to user space?
- Using large folios for text areas: the kernel's readahead code works well for data, but tends to break up executable code (text) into small chunks. Some minor changes could improve that situation.
- Two approaches to better kernel samepage merging: a pair of sessions on how the system can do more focused and synchronous deduplication of memory.
- Improving hot-page detection and promotion: the ongoing challenge of figuring out which memory is in the most active use at any given time.
- A strange BPF error message: Yonghong Song explains how undefined behavior can turn a simple uninitialized variable into a puzzling error from the BPF verifier.
- An update on pahole: Arnaldo Carvalho de Melo gives an update on how development of the pahole debugging-information manipulation tool has gone over the past year.
- A new type of spinlock for the BPF subsystem: Deadlocks are a recurring problem for BPF, one that complicates the handling of locks in BPF programs. A new lock design may help prevent them.