All posts by corbet

Barnes: Parallel ./configure

Post Syndicated from corbet original https://lwn.net/Articles/1019303/

Tavian Barnes takes on
the tedious process of waiting for configure scripts to run.

I paid good money for my 24 CPU cores, but ./configure can only
manage to use 69% of one of them. As a result, this random project
takes about 13.5× longer to configure the build than it does to
actually do the build.

The purpose of a ./configure script is basically to run the
compiler a bunch of times and check which runs succeeded. In this
way it can test whether particular headers, functions, struct
fields, etc. exist, which lets people write portable software. This
is an embarrassingly parallel problem, but Autoconf can’t
parallelize it, and neither can CMake, neither can Meson, etc.,
etc.

(Thanks to Paul Wise).

[$] Cache awareness for the CPU scheduler

Post Syndicated from corbet original https://lwn.net/Articles/1018334/

The kernel’s CPU scheduler has to balance a wide range of objectives. The
tasks in the system must be scheduled fairly, with latency for any given
task kept within bounds. All of the CPUs in the system should be kept busy
if there is enough work to do, but unneeded CPUs should be shut down to
reduce power consumption. A task should also run on the CPU that is most
likely to have cached the memory that task is using. This patch
series from Chen Yu aims to improve how the scheduler handles cache
locality for multi-threaded processes.

Signing key change for Kali Linux

Post Syndicated from corbet original https://lwn.net/Articles/1019255/

The Kali Linux distribution has announced
that software updates will soon start failing for all users:

This is not only you, this is for everyone, and this is entirely
our fault. We lost access to the signing key of the repository, so
we had to create a new one. At the same time, we froze the
repository (you might have noticed that there was no update since
Friday 18th), so nobody was impacted yet. But we’re going to
unfreeze the repository this week, and it’s now signed with the new
key.

The announcement includes instructions for how to recover from the problem.

Security updates for Tuesday

Post Syndicated from corbet original https://lwn.net/Articles/1019272/

Security updates have been issued by AlmaLinux (glibc, php:8.1, and thunderbird), Debian (libreoffice), Fedora (caddy), Mageia (chromium-browser-stable), Red Hat (php:8.1), SUSE (glow), and Ubuntu (kicad, linux-aws-5.15, linux-azure-nvidia, linux-gcp-5.15, mistral, python-mistral-lib, tomcat8, and trafficserver).

Security updates for Friday

Post Syndicated from corbet original https://lwn.net/Articles/1018912/

Security updates have been issued by AlmaLinux (thunderbird), Debian (libbpf), Fedora (golang-github-openprinting-ipp-usb, ImageMagick, mingw-libsoup, mingw-poppler, and pgbouncer), SUSE (glib2, govulncheck-vulndb, libsoup-2_4-1, libxml2-2, mozjs60, ruby2.5, and thunderbird), and Ubuntu (linux, linux-azure, linux-azure-5.4, linux-bluefield, linux-gcp, linux-hwe-5.4, linux-ibm, linux-kvm, linux-oracle, linux-oracle-5.4, linux-aws, linux-aws-5.4, linux-gcp-5.4, linux-iot, linux-aws-fips, linux-azure-fips, linux-fips, linux-gcp-fips, linux-hwe-6.8, linux-ibm-5.4, linux-oracle-5.15, openssh, and php-twig).

[$] Some __nonstring__ turbulence

Post Syndicated from corbet original https://lwn.net/Articles/1018486/

New compiler releases often bring with them new warnings; those warnings
are usually welcome, since they help developers find problems before they
turn into nasty bugs. Adapting to new warnings can also create disruption
in the development process, though, especially when an important developer
upgrades to a new compiler at an unfortunate time. This is just the
scenario that played out with the 6.15-rc3
kernel release and the implementation of
-Wunterminated-string-initialization in GCC 15.

[$] DMA addresses for UIO

Post Syndicated from corbet original https://lwn.net/Articles/1017449/

The Userspace
I/O (UIO) subsystem was first added to the kernel by
Hans J. Koch for the 2.6.32 release in 2007. Its purpose is to facilitate
the writing of drivers (mostly) in user space; to that end, it provides
access to a number of resources that user-space code normally cannot touch.
One piece that is missing, though, is DMA addresses. A proposal to
fill that gap from Bastien Curutchet is running into some opposition,
though.

Security updates for Tuesday

Post Syndicated from corbet original https://lwn.net/Articles/1018444/

Security updates have been issued by AlmaLinux (java-1.8.0-openjdk, kernel, libxslt, mod_auth_openidc:2.3, and webkit2gtk3), Fedora (c-ares, giflib, jupyterlab, perl, perl-Devel-Cover, perl-PAR-Packer, prometheus-podman-exporter, python-notebook, python-pydantic-core, rpki-client, ruby, rust-adblock, rust-cookie_store, rust-gitui, rust-gstreamer, rust-icu_collections, rust-icu_locid, rust-icu_locid_transform, rust-icu_locid_transform_data, rust-icu_normalizer, rust-icu_normalizer_data, rust-icu_properties, rust-icu_properties_data, rust-icu_provider, rust-icu_provider_macros, rust-idna, rust-idna_adapter, rust-litemap, rust-ron, rust-sequoia-openpgp, rust-sequoia-openpgp1, rust-tinystr, rust-url, rust-utf16_iter, rust-version-ranges, rust-write16, rust-writeable, rust-zerovec, rust-zip, thunderbird, and uv), SUSE (erlang, erlang26, and govulncheck-vulndb), and Ubuntu (mosquitto).

EU OS: A European Proposal for a Public Sector Linux Desktop (The New Stack)

Post Syndicated from corbet original https://lwn.net/Articles/1018058/

The New Stack looks
at EU OS, an attempt to create a desktop system for the European public
sector.

EU OS is not a brand-new Linux distribution in the traditional
sense. Instead, it is a proof-of-concept built atop Fedora’s
immutable KDE Plasma spin (Kinoite). EU OS takes a layered approach
to customization. The project’s vision is to provide a standard,
adaptable Linux base that can be extended with national, regional
or sector-specific customizations, making it suitable for a wide
range of European public sector needs.

[$] The problem of unnecessary readahead

Post Syndicated from corbet original https://lwn.net/Articles/1016860/

The final session in the memory-management track of the 2025 Linux Storage,
Filesystem, Memory-Management, and BPF Summit was a brief, last-minute
addition run by Kalesh Singh. The kernel’s readahead mechanism is
generally good for performance; it ensures that data is present by the time
an application gets around to asking for it. Sometimes, though, readahead
can go a little too far.

[$] Memory controller performance improvements

Post Syndicated from corbet original https://lwn.net/Articles/1016856/

The kernel’s memory controller works within the control-group mechanism to
enforce memory-usage limits on groups of processes. This component has
often had performance problems, so there is continual interest in
optimizing it. Shakeel Butt led a session during the memory-management
track of the 2025 Linux Storage, Filesystem, Memory-Management, and BPF
Summit to look at the current state of the memory controller and what can
be done to reduce its overhead.

[$] Improvements for the contiguous memory allocator

Post Syndicated from corbet original https://lwn.net/Articles/1016844/

As a system runs, its memory becomes fragmented; it does not take long
before the allocation of large, physically contiguous memory ranges becomes
difficult or impossible. The contiguous memory
allocator (CMA) is a kernel subsystem that attempts to address this
problem, but it has never worked as well as some would like. Two sessions
in the memory-management track at the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit looked at how CMA can be improved; the
first looked at providing guaranteed allocations, while the second
addressed some inefficiencies in CMA.