All posts by corbet

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.

MITRE Warns CVE Program Faces Disruption (Security Week)

Post Syndicated from corbet original https://lwn.net/Articles/1017565/

Security Week is one of several outlets reporting
that the funding for the CVE program at MITRE disappears as of
April 16.

Maintained by MITRE Corporation, a not-for-profit organization that
operates federal R&D centers, the CVE program is funded through
multiple channels, including the U.S. government, industry
partnerships, and international organizations.

Earlier this month, in anticipation of the US government funding
cuts, MITRE initiated layoffs that affected more than 400 employees
in its Virginia office. The cuts were ordered after the Trump
administration announced more than $28 million in canceled
contracts for the company.

[$] Automatic tuning for weighted interleaving

Post Syndicated from corbet original https://lwn.net/Articles/1016842/

It is common, on NUMA systems, to try to allocate all memory on the local
node, since it will be the fastest. That is not the only possible policy,
though; another is weighted interleaving,
which seeks to distribute allocations across memory controllers to maximize
the bandwidth utilization on each. Configuring such policies can be
challenging, though. At the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit, Joshua Hahn ran a session in the
memory-management track about how that configuration might be automated.

[$] The state of the memory-management development process, 2025 edition

Post Syndicated from corbet original https://lwn.net/Articles/1016724/

Andrew Morton, the lead maintainer for the kernel’s memory-management
subsystem, tends to be quiet during the Linux Storage, Filesystem,
Memory-Management, and BPF Summit, preferring to let the developers work
things out on their own. That changes, though, when he leads the
traditional development-process session in the memory-management track. At
the 2025 gathering, this discussion covered a number of ways in which the
process could be improved, but did not unearth any significant problems.

[$] Managing multiple sources of page-hotness data

Post Syndicated from corbet original https://lwn.net/Articles/1016722/

Knowing how frequently accessed a page of memory is (its “hotness”) is a
key input to many memory-management heuristics. Jonathan Cameron, in a
memory-management track at the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit, pointed out that the number of sources
of that kind of data is growing over time. He wanted to explore the
questions of what commonality exists between data from those sources, and
whether it makes sense to aggregate them all somehow.

[$] Management of volatile CXL devices

Post Syndicated from corbet original https://lwn.net/Articles/1016718/

Compute
Express Link (CXL) memory is not like the ordinary RAM that one might
install into a computer; it can come and go at any time and is often not
present when the kernel is booting. That complicates the management of
this memory. During the memory-management track of the 2025 Linux Storage,
Filesystem, Memory-Management, and BPF Summit, Gregory Price ran a session
on the challenges posed by CXL and how they might be addressed.

[$] Preparing DAMON for future memory-management problems

Post Syndicated from corbet original https://lwn.net/Articles/1016525/

The Data Access
MONitor (DAMON) subsystem provides access to detailed memory-management
statistics, along with a set of tools for implementing policies based on
those statistics. An update on DAMON by its primary author, SeongJae Park,
has been a fixture of the Linux Storage, Filesystem, Memory-Management, and
BPF Summit for some years. The 2025 Summit was no exception; Park led two
sessions on recent and future DAMON developments, and how DAMON might
evolve to facilitate a more access-aware memory-management subsystem in the
future.

[$] Improving hot-page detection and promotion

Post Syndicated from corbet original https://lwn.net/Articles/1016519/

Tiered-memory systems feature multiple types of memory with varying
performance characteristics; on such systems, good performance depends on
keeping the most frequently used data in the fastest memory. Identifying
that data and placing it properly is a challenge that has kept developers
busy for years. Bharata Rao, presenting remotely during a
memory-management-track session at the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit, led a discussion on a potential solution he has recently
posted; Raghavendra K T was also named on the
session proposal. It seems likely, based on the discussion, that
developers working in this area will not run out of problems anytime soon.

[$] Two approaches to better kernel samepage merging

Post Syndicated from corbet original https://lwn.net/Articles/1016426/

The kernel
samepage merging (KSM) subsystem works by finding pages in memory with
the same contents, then replacing the duplicated copies with a single,
shared copy. KSM can improve memory utilization in a system, but has some
problems as well. In two memory-management-track sessions at the 2025
Linux Storage, Filesystem, Memory-Management, and BPF Summit, Mathieu
Desnoyers and Sourav Panda proposed improvements to KSM to
make it work better for specific use cases.

[$] Using large folios for text areas

Post Syndicated from corbet original https://lwn.net/Articles/1016416/

Quite a bit of work has been done in recent years to allow the kernel to
make more use of large folios. That progress has not yet reached the
handling of text (executable code) areas, though. During the
memory-management track of the 2025 Linux Storage, Filesystem,
Memory-Management, and BPF Summit, Ryan Roberts ran a session on how that
situation might be improved. It would be a relatively small and contained
operation, but can give a measurable performance improvement.

[$] Per-CPU memory for user space

Post Syndicated from corbet original https://lwn.net/Articles/1016408/

The kernel makes extensive use of per-CPU data as a way to avoid contention
between processors and improve scalability. Using the same technique in
user space is harder, though, since there is little control over which CPU
a process may be running on at any given time. That hasn’t stopped Mathieu
Desnoyers from trying, though; in the memory-management track of the 2025
Linux Storage, Filesystem, Memory-Management, and BPF Summit, he presented
a proposal for how user-space per-CPU memory could work.