Hírolvasó

[$] The path to deprecating SPARSEMEM

Linux Weekly News
1 év 3 hónap óta
The term "memory model" is used in a couple of ways within the kernel. Perhaps the more obscure meaning is the memory-management subsystem's view of how physical memory is organized on a given system. A proper representation of physical memory will be more efficient in terms of memory and CPU use. Since hardware comes in numerous variations, the kernel supports a number of memory models to match; see this article for details. At the 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit, Oscar Salvador, presenting remotely, made the case for removing one of those models.
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[$] Documenting page flags by committee

Linux Weekly News
1 év 3 hónap óta
For every page of memory in the system, the kernel maintains a set of page flags describing how the page is used and various aspects of its current state. Space for page flags has been in chronic short supply, leading to a desire to eliminate or consolidate them whenever possible. That objective, though, is hampered by the fact that the purpose of many page flags is not well understood. In a memory-management-track session at the 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit, Matthew Wilcox set out to cooperatively update the page-flag documentation to improve that situation.
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[$] Merging msharefs

Linux Weekly News
1 év 3 hónap óta
The problem of sharing page tables across processes has been discussed numerous times over the years, Khalid Aziz said at the beginning of his 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit session on the topic. He was there to, once again, talk about the proposed mshare() system call (which, in its current form, is no longer actually a system call but the feature still goes by that name) and to see what can be done to finally get it into the mainline.
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[$] Toward the unification of hugetlbfs

Linux Weekly News
1 év 3 hónap óta
The kernel's hugetlbfs subsystem was the first mechanism by which the kernel made huge pages available to user space; it was added to the 2.5.46 development kernel in 2002. While hugetlbfs remains useful, it is also viewed as a sort of second memory-management subsystem that would be best unified with the rest of the kernel. At the 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit, Peter Xu raised the question of what that unification would involve and what the first steps might be.
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[$] The KeePassXC kerfuffle

Linux Weekly News
1 év 3 hónap óta

KeePassXC is an open-source (GPLv3), cross-platform password manager with local-only data storage. The project comes with a number of build options that can be used to toggle optional features, such as browser integration and password database sharing. However, controversy ensued when Debian Developer Julian Klode decided to make use of these compile flags to disable these features to improve security in the keepassxc package uploaded to Debian unstable for the upcoming Debian 13 ("Trixie") release.

jzb

[$] The interaction between memory reclaim and RCU

Linux Weekly News
1 év 3 hónap óta
The 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit was a development conference, where discussion was prioritized and presentations with a lot of slides were discouraged. Paul McKenney seemingly flouted this convention in a joint session of the storage, filesystem, and memory-management tracks where he presented about 50 slides — in five minutes, twice. The subject was the use of the read-copy-update (RCU) mechanism in the memory-reclaim process, and whether changes to RCU would be needed for that purpose.
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[$] Faster page faults with RCU-protected VMA walks

Linux Weekly News
1 év 3 hónap óta
Looking up a virtual memory area (VMA) in a process's address space, for the handling of page faults or any of a number of other tasks, in multi-threaded processes has long been bedeviled by lock contention in the kernel. As a result, developer gatherings have been subjected to many sessions on how to improve the situation. At the 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit, developers in the memory-management track met, in a session led by Liam Howlett, to talk about a situation that has improved considerably in recent times, but which still offers opportunities for optimization.
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Security updates for Wednesday

Linux Weekly News
1 év 3 hónap óta
Security updates have been issued by Debian (webkit2gtk), Fedora (kernel), Mageia (chromium-browser-stable, djvulibre, gdk-pixbuf2.0, nss & firefox, postgresql15 & postgresql13, python-pymongo, python-sqlparse, stb, thunderbird, and vim), Red Hat (go-toolset:rhel8, nodejs, and varnish:6), SUSE (gitui, glibc, and kernel), and Ubuntu (libspreadsheet-parseexcel-perl, linux-aws, linux-aws-5.15, linux-gke, linux-gcp, python-idna, and thunderbird).
jzb

[$] Virtual machine scheduling with BPF

Linux Weekly News
1 év 3 hónap óta

Vineeth Pillai gave a remote talk at the 2024 Linux Storage, Filesystem, Memory Management, and BPF Summit explaining how BPF could be used to improve the performance of virtual machines (VMs). Pillai has a patch set designed to let guest and host machines share scheduling information in order to eliminate some of the overhead of running in a VM. The assembled developers had several comments on the design, but seemed overall to approve of the prospect.

daroc

Important message for Apple Silicon OpenBSD/arm64 users

OpenBSD Journal
1 év 3 hónap óta
As you may be aware, OpenBSD runs on Apple Silicon M series processors, thanks to the efforts of the OpenBSD/arm64 developers.

For those running our favorite operating system alongside the Apple product, sometimes special measures are needed, though.

Mark Kettenis (kettenis@) sent a message titled Important message for Apple Silicon OpenBSD/arm64 users to the misc@ and arm@ mailing lists, warning about possible firmware issues:

Subject: Important message for Apple Silicon OpenBSD/arm64 users From: Mark Kettenis <mark.kettenis () xs4all ! nl> Date: 2024-05-21 20:54:21 As indicated here: https://social.treehouse.systems/@AsahiLinux/112449204541186432 The system firmware that comes with macOS Sonoma 14.5 triggers a bug in the m1n1 bootloader that is used to boot OpenBSD on these machines. The bug will prevent OpenBSD from booting on some machines after the macOS update has been installed. The recommended fix is to update the "stage1" m1n1 by booting into macOS and running:

Read more…

[$] Another try for address-space isolation

Linux Weekly News
1 év 3 hónap óta
Brendan Jackman started his memory-management-track session at the 2024 Linux Storage, Filesystem, Memory-Management and BPF Summit by saying that, for some years now, the kernel community has been stuck in a reactive posture with regard to hardware vulnerabilities. Each problem shows up with its own scary name, and kernel developers find a way to mitigate it, usually losing performance in the process. Jackman said that it is time to take back the initiative against these vulnerabilities by reconsidering the more general use of address-space isolation.
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