The physical memory in a computer system is a precious resource, so a lot of effort has been put into managing it effectively. This task is made more difficult by the complexity of the memory architecture on contemporary systems. There are several layers of abstraction that deal with the details of how physical memory is laid out; one of those is simply called the "memory model". There are three models supported in the kernel, but one of them is on its way out. As a way of understanding this change, this article will take a closer look at the evolution of the kernel's memory models, their current state, and their possible future.

Security updates have been issued by Debian (curl, jackson-databind, minissdpd, php5, thunderbird, wireshark, and wpa), Fedora (curl, drupal7, firefox, kernel, libmediainfo, mediaconch, mediainfo, mod_http2, mupdf, rust, and singularity), openSUSE (containerd, docker, docker-runc, go, go1.11, go1.12, golang-github-docker-libnetwork), Oracle (firefox and libvirt), Scientific Linux (firefox and libvirt), and SUSE (bluez, curl, gnutls, java-1_7_1-ibm, libu2f-host, libvirt, python3, screen, and xen).

The second 5.2 kernel prepatch is out for testing. "Fairly normal rc2, no real highlights - I think most of the diff is the SPDX updates. Who am I kidding? The highlight of the week was clearly Finland winning the ice hockey world championships." The codename has been changed to "Golden Lions".

The latest set of stable kernel updates is 5.1.5, 5.0.19, 4.19.46, 4.14.122, and 4.9.179. Each contains yet another set of important fixes.

Several new system calls have been proposed for addition to the kernel in a near-future release. A few of those, in particular, focus on memory-management tasks. Read on for a look at process_vm_mmap() (for zero-copy data transfer between processes), and two new APIs for advising the kernel about memory use in a different process.

Security updates have been issued by Debian (zookeeper), Fedora (kernel, singularity, and thunderbird), openSUSE (java-1_8_0-openjdk), Oracle (curl), Red Hat (firefox, libvirt, and virt:rhel), SUSE (php5, python-Jinja2, python-Pillow, and sysstat), and Ubuntu (MariaDB).

The linux-kernel mailing list has recently seen more than the usual amount of traffic proposing new system calls. LWN is endeavoring to catch up with that stream, starting with a couple of proposals for the management of file descriptors. pidfd_open() is a new way to create a "pidfd" file descriptor that refers to a process in the system, while close_range() is an efficient way to close many open descriptors with a single call.

Security updates have been issued by Debian (ffmpeg and firefox-esr), openSUSE (bzip2, chromium, and GraphicsMagick), Slackware (curl), SUSE (ucode-intel), and Ubuntu (curl and intel-microcode).

The LWN.net Weekly Edition for May 23, 2019 is available.

One thing that is known about using transparent huge pages (THPs) for filesystems is that it is a hard problem to solve, but is there a solid first step that could be taken toward that goal? That is the question Song Liu asked to open his combined filesystem and memory-management session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). His employer, Facebook, has a solid use case for using THPs on files in the page cache, which may provide a starting point.

Amir Goldstein has a use case for a feature that could be called a "lazy file reflink", he said, though it might also be described as "VFS-level snapshots". He went through the use case, looking for suggestions, in a session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). He has already implemented parts of the solution, but would like to get something upstream, which would mean shifting from the stacked-filesystem approach he has taken so far.

The openSUSE project has announced the release of openSUSE Leap 15.1. "Leap releases are scalable and both the desktop and server are equally important for professional’s workloads, which is reflected in the installation menu as well as the amount of packages Leap offers and hardware it supports. Leap is well suited and prepared for usage as a Virtual Machine (VM) or container guest, allowing professional users to efficiently run network services no matter whether it’s a single server or a data center."

Stable kernels 5.1.4, 5.0.18, 4.19.45, 4.14.121, and 4.9.178 have been released. They all contain important fixes and users should upgrade.

Security updates have been issued by CentOS (ruby and wget), Debian (proftpd-dfsg), Fedora (firefox, mupdf, nss, and wavpack), openSUSE (evolution, GraphicsMagick, graphviz, libxslt, openssl-1_0_0, ovmf, and sqlite3), Red Hat (dotnet, python27-python and python27-python-jinja2, and rh-mariadb102-mariadb and rh-mariadb102-galera), Slackware (mozilla), SUSE (gnutls, java-1_7_1-ibm, and java-1_8_0-ibm), and Ubuntu (curl, firefox, php5, and webkit2gtk).

Version 8.5 of the Tor Browser is out. "Tor Browser 8.5 is the first stable release for Android. Since we released the first alpha version in September, we've been hard at work making sure we can provide the protections users are already enjoying on desktop to the Android platform. Mobile browsing is increasing around the world, and in some parts, it is commonly the only way people access the internet. In these same areas, there is often heavy surveillance and censorship online, so we made it a priority to reach these users."

The cost of fsync() is well known to filesystem developers, which is why there are efforts to provide cheaper alternatives. Ric Wheeler wanted to discuss the longstanding idea of adding an asynchronous version of fsync() in a filesystem session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). It turns out that what he wants may already be available via the new io_uring interface.

The Mozilla blog takes a look at the Firefox 67 release. "Today’s new Firefox release continues to bring fast and private together right at the crossroads of performance and security. It includes improvements that continue to keep Firefox fast while giving you more control and assurance through new features that your personal information is safe while you’re online with us." See the release notes for more information.

The "guarantees" that existing filesystems make with regard to persistence in the face of a system crash was the subject of a session led by Amir Goldstein at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). The problem is that filesystem developers are not willing to make much in the way of guarantees unless applications call fsync()—something that is not popular with application developers, who want a cheaper option.

The kernel mailing lists carry the sad news that longtime kernel contributor and subsystem maintainer Martin Schwidefsky has been killed in an accident. "Martin was the most significant contributor to the initial s390 port of the Linux Kernel and later the maintainer of the s390 architecture backend. His technical expertise as well as his mentoring skills were outstanding. Martin was well known for his positive mindset and his willingness to help. He will be greatly missed."

The relationship between SUSE and the openSUSE community is currently under discussion as the community considers different options for how it wants to be organized and governed in the future. Among the options under consideration is the possibility of openSUSE setting up an entirely independent foundation, as it seeks greater autonomy and control over its own future and operations.