Martin Lau gave a talk in the BPF track of the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit about a performance problem plaguing the networking subsystem, and some potential ways to fix it. He works on BPF programs that need to store socket-local data; amid other improvements to the networking and BPF subsystems, retrieving that data has become a noticeable bottleneck for his use case. His proposed fix prompted a good deal of discussion about how the data should be laid out.

Modern compilers perform a lot of optimizations, which can complicate debugging. Song Liu and Thierry Treyer spoke about a potential improvement to BPF Type Format (BTF) debugging information that could partially combat that problem at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. They want to add information on selectively inlined functions to BTF in order to better support tracing tools. Treyer participated remotely.

Linux systems can have large filesystems; trying to keep up with the stream of fanotify filesystem-monitoring notifications for them can be a struggle. Fanotify is one of a few ways to monitor accesses to filesystems provided by the kernel. Song Liu led a discussion on how to improve in-kernel filtering of fanotify events to a joint session of the filesystem and BPF tracks at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. He wants to combine the best parts of a few different approaches to efficiently filter filesystem events.

Anton Protopopov led a short discussion at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit about amount of memory used by hash tables in BPF programs. He thinks that the current memory layout is inefficient, and wants to split the structure that holds table entries into two variants for different kinds of maps. When that proposal proved uncontroversial, he also took the chance to talk about a bug in BPF's call instruction.

Greg Kroah-Hartman has announced the release of the 6.14.6, 6.12.28, 6.6.90, 6.1.138, and 5.15.182 stable kernel versions.

BPF arenas are areas of memory where the verifier can safely relax its checking of pointers, allowing programmers to write arbitrary data structures in BPF. Emil Tsalapatis reported on how his team has used arenas in writing sched_ext schedulers at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit. His biggest complaint was about the fact that kernel pointers can't be stored in BPF arenas — something that the BPF developers hope to address, although there are some implementation problems that must be sorted out first.

From servers in a data center to desktop computers, many devices communicating on a network will eventually have to filter network traffic, whether it's for security or performance reasons. As a result, this is a domain where a lot of work is put into improving performance: a tiny performance improvement can have considerable gains. Bpfilter is a project that allows for packet filtering to easily be done with BPF, which can be faster than other mechanisms.

Ihor Solodrai has been working on the BPF subsystem's continuous-integration (CI) testing for the last six months. At the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit, he remotely shared an update on his work, and solicited feedback on how the tests could be further improved. Much of the work he's done has been specific to the BPF subsystem, but some is more generic and could potentially be of use to other subsystems. He also shared some general lessons learned from working on the BPF CI tests.

The BPF verifier is an increasingly complex and security-critical piece of code. When the kinds of people who are apt to work on BPF see a situation like that, they naturally question whether it's possible to use formal verification to ensure that the implementation of the code in question is correct. Santosh Nagarakatte led the first of two extra-long sessions in the BPF track of the 2025 Linux Storage, Filesystem, Memory Management, and BPF Summit about his team's work formally verifying the BPF verifier with a custom tool called Agni.

Srinivas Narayana led a remote session about extending Agni to prove the correctness of the BPF verifier's handling of different execution paths as part of the Linux Storage, Filesystem, Memory Management, and BPF Summit. The problem of ensuring the correctness of path exploration is much more difficult than the problem of ensuring the correctness of arithmetic operations (which was the subject of the previous session), however. Narayana's plan to tackle the problem makes use of a mixture of specialized techniques — and may need some assistance from the BPF developers to make it feasible at all.

Mahé Tardy led two sessions about some of the challenges that he, Kornilios Kourtis, and John Fastabend have run into in their work on Tetragon (Apache-licensed BPF-based security monitoring software) at the Linux Storage, Filesystem, Memory Management, and BPF Summit. The session prompted discussion about the feasibility of letting BPF programs send data over the network, as well as potential new kfuncs to let BPF firewalls send TCP reset packets. Tardy presented several possible ways that these could be accomplished.

As of this writing, 5,546 non-merge changesets have been pulled into the mainline kernel repository for the 6.16 release. This is a bit less than half of the total commits for 6.15, so the merge window is well on its way. Read on for our summary of the first half of the 6.16 merge window.

This year's Linaro Connect in Lisbon, Portugal featured a number of talks about the use of open-source components in safety-critical systems. Kate Stewart gave a keynote on the topic on the first day of the conference. In it, she highlighted several projects that have been working to pursue safety certification and spoke about the importance of being able to trace software's origins to safety. In a talk on the second day, Roberto Bagnara shared his experience with working on one of those projects, the Xen hypervisor, to conform to a formal set of rules for safety-critical code.

Cong Wang and Daniel Borkmann each led session at the 2025 Linux Storage, Filesystem, Memory Management, and BPF Summit about their respective plans to speed up networking in the Linux kernel. Both sessions described ways to remove unnecessary operations in the networking stack, but they focused on different areas. Wang spoke about using BPF to speed up socket operations, while Borkmann spoke about eliminating the overhead of networking operations on virtual machines.

The European Union's Cyber Resilience Act (CRA) has caused a stir in the software-development world. Thanks to advocacy by the Eclipse Foundation, Open Source Initiative, Linux Foundation, Mozilla, and others, open-source software projects generally have minimal requirements under the CRA — but nothing to do with law is ever quite so simple. Marta Rybczyńska spoke at Linaro Connect 2025 about the impact of the CRA on the open-source ecosystem, with an emphasis on the importance of understanding a project's role under the CRA. She later participated in a panel discussion with Joakim Bech, Kate Stewart, and Mike Bursell about how the CRA would impact embedded open-source development.

The 6.16 merge window closed on June 8, as expected, containing 12,899 non-merge commits. This is slightly more than the 6.15 merge window, but well in line with expectations. 7,353 of those were merged after the summary of the first half of the merge window was written. More detailed statistics can be found in the LWN kernel source database.