Linux Plumbers Conference 2021

Session

LPC Refereed Track

20 Sept 2021, 07:00

77. Rust in the Linux ecosystem

Miguel Ojeda

20/09/2021, 07:00

Rust is a systems programming language that is getting stronger support by many companies and projects over time, thanks to its memory-safety innovations (e.g. the safe/unsafe split, the borrow checker, etc.).

This talk covers:

• A quick introduction to the Rust language.
• What exactly means "safety" in the context of Rust, and which kind of issues Rust prevents (e.g. data races,...

45. rustc_codegen_gcc: A gcc codegen for the Rust compiler

Antoni Boucher

20/09/2021, 08:00

The Rust programming language is becoming more and more popular: it's even considered as another language allowed in the Linux kernel.
That brought up the question of architecture support as the official Rust compiler is based on LLVM.
This project, rustc_codegen_gcc, is meant to plug the GCC backend to the Rust compiler frontend as a relatively low-effort: it's a shared library reusing the...

54. GCC Front-End for Rust

Philip Herron (Embecosm)

20/09/2021, 09:00

GCC Rust is a front-end project for the GNU toolchain, a work-in-progress alternative to the official Rustc compiler. Being part of GCC, the compiler benefits from the common compiler flags, available backend targets and provides insight into its distinct optimiser's impact on a modern language.

This project dates back to 2014 where Rust was still ~0.8, but the language was subject to...

70. Formalizing Kernel Synchronization Primitives with PREEMPT_RT

Ahmed S. Darwish

20/09/2021, 10:00

In certain corners of the Linux Kernel, manual locking and lockless-synchronization primitives are developed instead of using the existing (and default) kernel locking APIs. This is obviously frowned upon, but still exists for historical reasons or because developers think that the subsystem in question is special enough to warrant manual synchronization primitives.

Adopting the PREEMPT_RT...

21. Understanding motivations, goals and challenges faced by the Linux Kernel contributors

Bianca Trinkenreich (Northern Arizona University)

21/09/2021, 07:00

Motivation to contribute and barriers faced by newcomers and contributors to join and stay in Open Source Software projects have been intriguing researchers since the early 2000s. The literature on motivation was updated on recent work and showed that for more than 55% of contributors who answered the questionnaire, the motivation shifted after joining. Those contributors joined OSS for one...

79. Adding features to perf using BPF

Arnaldo Carvalho de Melo (Red Hat Inc.), Song Liu, Namhyung Kim

21/09/2021, 08:00

The availability of BPF allows the improvement of preexisting perf features or the
addition of new ones without requiring kernel changes.

The first use of BPF to augment perf is to use BPF programs to profile other BPF
programs with 'perf stat', this is already upstream and set the stage for
further uses. This provides functionality similar to 'bpftool prog profile' while reusing
lots...

74. Overview of memory reclaim in the current upstream kernel

Vlastimil Babka (SUSE)

21/09/2021, 09:00

It is generally known that Linux memory reclaim uses LRU ordered lists to decide which pages to evict to free memory for new pages. It might be less known that there are separate lists for file (page cache) and anonymous pages, and that both are further split in active and inactive parts. There are however lots of subtle details of how the relative sizes of these four lists are balanced, and...

31. Strange kernel performance changes - analysis and mitigation

Mr Feng Tang

21/09/2021, 10:00

0day bot has reported many strange kernel performance changes that the bisected culprit commits have nothing to do with the benchmark, which make patch authors confused or even annoyed. Debug shows these mostly are related to the random code/text alignments changes, false sharing, or adjacent cacheline prefetch, which is caused by the commit, as all components of kernel are flatly linked...

75. io_uring: BPF controlled I/O

Pavel Begunkov

22/09/2021, 07:00

io_uring is an asynchronous I/O API crafted for efficiency, where one of the reasons for using shared rings is to reduce context switching. It got lots of of features since introduction, and pushing it further we want to give away some of the control over submitting and controlling I/O to BPF, minimising the number of context switches even more.

• It should keep the number of system calls...

65. The Case for Memory Segregation

Alex Markuze (VMware)

22/09/2021, 08:00

In this talk, we would like to propose adding roles to memory pages. We contend that the current monochromatic memory model cannot address modern systems' security and performance needs.

We want to discuss two recent projects that perform memory segregation. DMA Aware Malloc for Networking (DAMN) that protects against DMA attacks (e.g., [project thundeclap][1]) while providing the same...

83. systemd-oomd: PSI-based OOM kills in systemd

Anita Zhang

22/09/2021, 09:00

Following a previous talk, [oomd: a userspace OOM killer][1], Facebook has since come up with a simplified interface for oomd that removes some of the barriers of configuring oomd. Integration with systemd allows more users to reuse their knowledge of configuring systemd daemons. And by removing some of the complexity of coming up with an OOM kill policy, we enable more users to do cgroup and...

32. A maintainable, scalable, and verifiable SW architectural design model for the Linux Kernel

Mr Gabriele Paoloni, Mr Daniel Bristot De Oliveira (Red Hat)

22/09/2021, 10:00

Over the last years, many discussions took place in Linux Foundation's ELISA workgroup (elisa.tech) about possible approaches to qualify Linux for safety-critical systems. It is a consensus that one of the main challenges for the qualification of Linux is the lack of SW Architectural Design documentation, especially concerning the kernel internal components/drivers/subsystems. Such...

47. Linux and Zephyr interoperability - the start of a beautiful relationship

Amit Kucheria (Linaro)

23/09/2021, 07:00

You're a company that is working on a suite of products that spans every conceivable gadget built for the smarthome - from a simple thermostat to security alarms, from set top boxes to internet gateways, mobile phones and tablets and even servers running in the cloud.

Linux is a fairly obvious choice to build these products on top of - it scales well for devices with more than 128MB of RAM...

20. The forefront of the development for NVDIMM on Linux Kernel

Mr Yasunori Goto (Fujitsu Ltd), Mr Shiyang Ruan (Nanjing Fujitsu Nanda Software Technology Co., Ltd)

23/09/2021, 08:00

NVDIMM (Non Volatile DIMM) is the most interesting device, because it has not only characteristic of memory but also storage.
To support NVDIMM, Linux kernel provides three access methods for users.
- Storage (Sector) mode
- Filesystem DAX(=Direct Access) mode
- Device DAX mode.

In the above three methods, Filesystem DAX is the most expected access method,
because applications can...

16. So you want to torture RCU?

Paul McKenney (Facebook)

23/09/2021, 09:00

Let's face it, using synchronization primitives such as RCU can be frustrating. And it is only natural to wish to get back, somehow, at the source of such frustration. In short, it is quite understandable to want to torture RCU. (And other synchronization primitives as well, but you have to start somewhere!) Another benefit of torturing RCU is that doing so sometimes uncovers bugs in other...

52. Protection Key Supervisor (PKS)

Rick Edgecombe (Co-worker)

23/09/2021, 10:00

Protection Key Supervisor provides fast, thread-specific manipulation of permission restrictions on kernel pages.

Multiple patch sets have been reviewed recently targeting an initial use case to provide stray write protection to persistent memory.

Persistent memory is mapped into the direct map and unlike regular DRAM it is particularly venerable to programming errors which would result...

40. Compute Express Link + Linux + QEMU = Yes

Ben Widawsky

24/09/2021, 07:00

Compute Express Link (CXL) is a cache coherent protocol designed to boost the performance of accelerators and memory expanders. By nature of being an open standard, it also allows vendors to design hardware which will work with a generic CXL driver in the same vein as AHCI, or NVMe (and others). With CXL 2.0 spec release late last year, we're starting to see usage models being actively pushed...

49. Bootconfig and kernel cmdline

Masami Hiramatsu (Linaro Ltd.)

24/09/2021, 08:00

In the recent kernel, Extra Boot Configuration (bootconfig) is available to pass the kernel boot parameters in the structured key-data form instead of single-line command line. The parameters passed via bootconfig are just merged to the kernel command line string(cmdline). Thus the kernel modules/subsystems can continue using kernel cmdline APIs, but can not use the bootconfig APIs for the...

55. Guider: Linux Tracing using Python

Peace Lee

24/09/2021, 09:00

There are various types of user-space tracing programs these days. But they are too versatile and each one has to be installed or difficult to use as a beginner.

This talk introduces Guider that provides various and powerful Linux tracing features using ftrace, ptrace, and procfs.
It's repository is https://github.com/iipeace/guider.

87. Measuring Code Review in the Linux Kernel Development Process

Ms Başak Erdamar, Lukas Bulwahn (BMW AG)

24/09/2021, 10:00

In this presentation, we show some work on Measuring Code Review in the Linux Kernel Development Process.

We investigated the following research questions:

• Does the number of responses increase as the patch developer is more experienced?
• Do maintainers get fewer or more responses than others, when they author a patch?
• Do patch developers who have previously been active in some...