LWN.net Weekly Edition for May 12, 2022

• Dealing with negative dentries: how the kernel can manage the cache of file-name lookup failures better.
• Recent RCU changes: a quick overview of read-copy-update (RCU) followed by descriptions of some of the bigger changes that have gone into it over the last few years.
• How to cope with hardware-poisoned page-cache pages: What should the kernel do when memory errors corrupt a page in the page cache?
• Page pinning and filesystems: this year's discussion on how to solve the problems with get_user_pages().
• Ways to reclaim unused page-table pages: a lot of the memory used to hold page tables is not needed in that role and could be put to better uses.
• The ongoing search for mmap_lock scalability: the 2022 version of the perennial page-fault scalability topic, perhaps with some solutions on the horizon this time.
• Improving memory-management documentation: how to capture some of the "tribal knowledge" behind memory management and make it available to more developers.
• The state of memory-management development: : Andrew Morton describes some changes to how memory-management patches are handled.
• Seeking an API for protection keys supervisor: protection keys can help to harden the kernel, but the best way of managing them is still unclear.
• Better tools for out-of-memory debugging: understanding out-of-memory problems is not easy; what can be done to improve the situation?
• Changing filesystem resize patterns: filesystems that are created small, but continually resized to be much larger, are causing some headaches.

today's leftovers

• Distro Delights, New Release Mania, Forking KDE, Windows in a Bottle

  If you are looking for a really cool Linux computing platform with lots of extras and a twist on traditional desktop design, check out Modicia OS Ultimate. Italy-based Modicia Web Design and Development Company recently released its latest upgrade — Modicia O.S. 22. You probably won’t stumble on this gem in hiding if you distro hop or browse through traditional outlets for Linux operating systems; but it is definitely a discovery worth finding. It is one of the easiest Linux offerings I have used. Modicia Ultimate installs without hassles and has no learning curve to get started. It is a great platform for personal and small business use as well. Get it here. The popular CentOS alternative, AlmaLinux, is now available on Oracle Cloud. AlmaLinux OS Foundation on May 5 announced its availability on the Oracle Cloud Infrastructure marketplace, continuing AlmaLinux’s penetration into the cloud.

• The Linux Foundation and Fintech Open Source Foundation Announce the Schedule for Open Source in Finance Forum London 2022, July 13

• OSI to the European Commission: make space for patent-free standards too

  One of the biggest hidden challenges facing the software and technology world is the evolving conflict between old electronics vendors and the new software-defined universe. It’s arising because of patents embedded within international standards. We think it needs fixing because it especially affects Open Source. It may come as a surprise to find that some supposedly “open“ standards – including those ratified by standards development organizations (SDOs) like ISO, CEN and ETSI – can’t be implemented without going cap-in-hand to the world’s largest companies to buy a license. This is because both the SDOs and regulators allow so-called SEPs – “standard-essential patents” – to be tolerated due to the legacy approach of standards in hardware contexts.

Programming Leftovers

• Interacting with the Pootle Bot on Gerrit

  Have you received “A polite ping, still working on this bug?” message on one of your Gerrit submissions? You can simply send an arbitrary reply to avoid the patch being abandoned within a month. Here we discuss more about Pootle bot, which is one of the QA (Quality Assurance) tools for the LibreOffice QA team to manage old submissions.

• Optimizing your QML application for compilation to C++

  This is the start of a series of posts where I'm going to share some insights on how to adjust a QML application to get the most out of qmlsc, the QML Script Compiler. In contrast to previous posts, I won't talk about the abstract architecture or the high level picture.

• Compiling QML to C++: Annotating JavaScript functions

  This is the second installment in the series on how to adjust your QML application to take the maximum advantage of qmlsc. In the first post we've set up the environment and taken an initial measurement. I highly recommend reading that one first.

• PaloAlto init-cfg.txt Bootstrap Config file Layout with Examples

  When you install and configure the PaloAlto firewall, when the firewall boots up for the first time, it does the bootstrapping process. PaloAlto uses the settings defined in the bootstrap files, including the init-cfg.txt and bootstrap.xml under the config folder to configure the initial state of the firewall.

• $30 compact multi-sensor board works with any microcontroller with I2C (Crowdfunding) - CNX Software

  SENSE is a compact multi-sensor board supporting measurement of air quality, sound, light intensity, temperature, proximity, etc… and designed by Zack Seifert, a seventeen-year-old electronics enthusiast and president of his school’s robotics team.

• I will just quickly do a blog post...

  I got ”inspired” by my writing of the previous blog post, and wrote in a channel about my experience some time ago. So why not also do a blog post about doing a blog post :) So… I was planning to use GitLab’s Pages feature via my Hugo fork as usual to push it through. So like, concentrate on writing and do a publish, right, like in good old times? I did so, but all I got both locally and in remote pipeline was stuff like…

• Rust: A Critical Retrospective

  Since I was unable to travel for a couple of years during the pandemic, I decided to take my new-found time and really lean into Rust. After writing over 100k lines of Rust code, I think I am starting to get a feel for the language and like every cranky engineer I have developed opinions and because this is the Internet I’m going to share them. The reason I learned Rust was to flesh out parts of the Xous OS written by Xobs. Xous is a microkernel message-passing OS written in pure Rust. Its closest relative is probably QNX. Xous is written for lightweight (IoT/embedded scale) security-first platforms like Precursor that support an MMU for hardware-enforced, page-level memory protection. In the past year, we’ve managed to add a lot of features to the OS: networking (TCP/UDP/DNS), middleware graphics abstractions for modals and multi-lingual text, storage (in the form of an encrypted, plausibly deniable database called the PDDB), trusted boot, and a key management library with self-provisioning and sealing properties. One of the reasons why we decided to write our own OS instead of using an existing implementation such as SeL4, Tock, QNX, or Linux, was we wanted to really understand what every line of code was doing in our device. For Linux in particular, its source code base is so huge and so dynamic that even though it is open source, you can’t possibly audit every line in the kernel. Code changes are happening at a pace faster than any individual can audit. Thus, in addition to being home-grown, Xous is also very narrowly scoped to support just our platform, to keep as much unnecessary complexity out of the kernel as possible.

• Huang: Rust: A Critical Retrospective

  Andrew 'bunnie' Huang has posted an extensive review of the Rust language derived from the experience of writing "over 100k lines" of code.

• This Week In Rust: This Week in Rust 443

• Caolán McNamara: Dark Style Preference with GTK

  Added something to track the org.freedesktop.appearance.color-scheme property as used by the GNOME 42 Dark Style Preference setting. Screencast recorded with the new iteration of GNOME's screen built-in recorder which is quite snazzy.