The io_uring subsystem is all about asynchronous execution; applications count on it to not block — unless explicitly requested to. Within io_uring, maintaining the "never blocks" guarantee has sometimes been a challenge, given that many paths in the kernel were never designed for asynchronous execution. This problem has been worked around, but at a significant cost to performance. Now, io_uring maintainer Jens Axboe has posted an RFC patch set with a somewhat radical (and potentially scary) solution to the problem.

Version 51 of the GNOME desktop environment has been released. The list of changes includes a number of performance improvements, offline data and better transit information in the Maps application, a new interface for the file previewer, and more.

Security updates have been issued by AlmaLinux (.NET 10.0, .NET 8.0, .NET 9.0, corosync, firewalld, kernel, kernel-rt, libevent, libsoup, microcode_ctl, nginx:1.26, python-lxml, rsyslog, tesseract, and unbound), Debian (firefox-esr, mkvtoolnix, thunderbird, and tor), Fedora (open62541, php-pecl-mongodb2, python-django6, python-jwcrypto, and roundcubemail), Mageia (aom, cockpit, libgd, packagekit, and python-h2), Red Hat (corosync, delve, git-lfs, grafana-pcp, gstreamer1-plugins-base, libvirt, opentelemetry-collector, and rhc-worker-playbook), Slackware (mozilla-firefox and mozilla-thunderbird), SUSE (acl, attr, alloy, ansible-core, clamav, containerized-data-importer, corosync, cups, distribution, glibc, google-cloud-sap-agent, govulncheck-vulndb, gvfs, helm, jq, kbd, kubernetes1.34-apiserver, kubernetes1.35-apiserver, lcms2, libcupsfilters, liblzmasdk26, libzypp, zypper, mistral-vibe, opensc, openvpn, pcre2, python-jwcrypto, tomcat, tomcat10, and tomcat11), and Ubuntu (guix, libheif, perl, python-cryptography, sqlite3, and valkey).

The Register looks forward to the upcoming Fedora 45 release.

The biggest surprise is that Linux's legacy in-kernel console – the text-mode interface normally hidden beneath the GUI – has been replaced with a software-controlled alternative. The replacement is kmscon, a userspace terminal emulator that has been in development for more than a decade.

Security updates have been issued by AlmaLinux (kernel, kernel-rt, libkcapi, nginx, nginx:1.24, openssl, osbuild-composer, perl, perl:5.32, python-tornado, rsync, and rust), Debian (cjose and nginx), Fedora (environment-modules, erlang, GitPython, knot, perl-Authen-SASL, python-configargparse, ruby, rubygems, and sblim-sfcb), Oracle (firefox, git-lfs, gstreamer1-plugins-base, kernel, libkcapi, nginx, nginx:1.26, openssl, osbuild-composer, perl, perl-YAML-Syck, postgresql18, python-tornado, and rust), Red Hat (fence-agents, git-lfs, microcode_ctl, osbuild-composer, podman, python-pyasn1, and resource-agents), SUSE (389-ds, ant, bson-devel, chirp-20260911, docker, gimp, google-cloud-sap-agent, hauler, kernel, kimi-code, libpcap, python-GitPython, python310, syncthing, yast2-samba-client, and zstd-jni), and Ubuntu (aom, imagemagick, kitty, openssh, phpseclib, policykit-1, python-sql, python-webob, shibboleth-sp, simplesamlphp, snapcast, srt, and suricata-update).

The scheduling of block I/O requests has long been a challenge for operating-system kernels. For many years, the performance characteristics of rotating drives meant that putting considerable resources into request ordering was worthwhile. In a world with fast, solid-state drives, scheduling is more concerned with enforcing fairness between competing users while being fast enough to keep up with drives that can perform millions of I/O operations per second. The blk-iocost I/O controller was designed for the solid-state world and generally performs well, but there is always a desire to do better. This patch series from Tao Cui aims to make blk-iocost more flexible by enabling the loading of a BPF program to make cost decisions.

Just a reminder that prices for LWN subscriptions will increase after September 15. Until then, the older rate still applies. See this article for details on this change. Thanks, yet again, to all of our subscribers for your support — that is what keeps LWN going.

The 7.3-rc3 kernel prepatch is out for testing. Linus said: "Another fairly large rc release, and again one with a bigger filesystem footprint that we usually see."

Kernel developers do a lot of kernel builds. Since the kernel is not a small program, those builds can take a fair amount of time, even on a fast machine. The kernel also has a complex build system; it is probably fair to say that few developers truly understand it, and fewer still are willing to try to improve it. Lorenzo Stoakes, armed with LLM-based assistance, decided to give it a try, though, and has managed to reduce the time it takes to build a kernel — and not by a small amount.

The restartable sequences feature is one of the stranger corners of the kernel's user-space interface; it provides a way for user space to carry out simple lockless operations and be informed if it is preempted over the course of an operation (and must, thus, restart). Work merged in the 6.19 release to improve the performance of restartable sequences broke the TCMalloc allocator, which was relying on an undocumented (and unintended) kernel behavior. Now, Olivier Dion is proposing an addition to the restartable-sequences API that will bring TCMalloc back into the fold; it does not make the restartable-sequences API any less strange, though.

The 7.3-rc2 kernel prepatch is out for testing. Linus said:

This didn't *feel* like a particularly busy rc2, but it clearly was. rc2 is usually the quietest time when people take a breather after the merge window and it takes a while to start finding bugs. But not this time - this is a "full fat" rc release. [...]

Nothing looks particularly odd, even if the rc2 timing is a bit unusual. It might be just random, but we'll obviously all blame it on AI, because whether that's really the cause or not, it's an easy thing to blame ;)

Tiered-memory systems are built with multiple types of memory, each of which has different performance characteristics. In addition to the usual DRAM, a tiered system might also provide faster high-bandwidth memory or slower CXL memory. On these systems, the placement of memory allocations has a significant effect on the performance that a workload will obtain. While work on tiered-memory improvements has been ongoing for years, it feels like the pace has slowed a bit recently. Even so, there are a few efforts underway, but they are facing questions about whether the tiering design makes sense.

The online publication industry, as a whole, is struggling, with challenges coming from multiple directions. Thanks to the support of all of you, our readers, LWN would appear to be doing better than most. But the world has changed around us and, in particular, prices have changed considerably. By now, you probably know where this is going: subscription prices at LWN will be increasing as of September 15.

By the time Linus Torvalds released 7.3-rc1 and closed the merge window for this release, 15,267 non-merge changesets had been pulled into the mainline repository. That is the second-highest commit count for an -rc1 release in the kernel's history; only the 6.7-rc1 release, which included nearly 3,000 commits of bcachefs history, had more. About 13,000 of those commits entered the mainline after the first 7.3 merge-window summary was written so, needless to say, there are a lot of changes to cover.

Linus has released 7.3-rc1 and closed the merge window for this release. "Nothing really stands out - except for the fact that it's big. It's not the biggest rc1 we've ever had, but it's certainly up there, at least in number of commits." He pulled 15,267 commits during this merge window, making it the second busiest ever; only 6.7 has exceeded it.

The results of the Debian general-resolution vote on the use of large language models have been posted; the winner is choice 5: Responsible Use of Generative AI.

Debian neither endorses nor prohibits the use of generative AI tools in the development, maintenance, or documentation of software, packaging, documentation, and other media published within the Debian Project. We recognize that such tools can substantially improve the productivity of contributors when used responsibly, allowing volunteers to spend more of their limited time on work that requires technical expertise, judgment, review, and collaboration.

The Debian Project nevertheless expects that all contributions submitted to Debian, regardless of how and with which tools they were produced, satisfy the same standards of quality, correctness, maintainability, and legal compliance. The use of a generative AI tool does not diminish the contributor's responsibility for the work they submit. Contributors are expected to understand, review, test, and, where appropriate, modify AI-assisted output before incorporating it into Debian.

Virtualization can increase CPU utilization by allowing a large number of virtual CPUs to share a smaller number of physical CPUs. The amount of CPU time that is actually available does not change, though, so heavy activity on too many virtual CPUs can lead to contention and significant performance loss. The steal governor patch series from Shrikanth Hegde is an attempt to address that problem with a mechanism that allows virtual machines to voluntarily reduce the number of virtual CPUs they use when contention is high.

For people who would like to experiment with the multi-kernel Linux concept, Cong Wang has announced the release of mklinux v7.0-mk2.

mklinux lets one machine run several independent Linux kernels at the same time on bare metal, without a hypervisor. A host kernel owns a pool of CPUs, memory and PCI devices, carves that pool into instances, and boots a spawn kernel into each instance through kexec_file_load(). Every spawn kernel runs natively on its own CPUs, its own physical memory and its own devices. Nothing is emulated and nothing is trapped; the only thing shared is what you choose to share.

Note that this is not the old MkLinux, which was a port to PowerPC Macintosh systems.

The 7.1.10, 6.18.46, 6.12.105, 6.6.153, 6.1.184, 5.15.217, and 5.10.266 stable kernels have all been released; each contains another set of important fixes.

From Jeremy Allison we have the sad news of the passing of Steve French. He was the maintainer of the kernel's SMB filesystem code for many years, having only dropped that role due to health issues in the last week. "I've known Steve for over 20 years. He was a legend in the community, and a really good friend. He will be greatly missed. Farewell Steve." He will indeed be missed.