All posts by corbet

[$] Debian’s which hunt

Post Syndicated from corbet original

One does not normally expect to see a great deal of angst over a one-page
shell script, even on the Internet. But Debian is special, so it has been
having an extended discussion over the fate of the which command
that has been escalated to the Debian Technical Committee. The amount of
attention that has been given to a small, nonstandard utility shines a
light on Debian’s governance processes and the interaction of tradition
with standards.

Kernel prepatch 5.15-rc7

Post Syndicated from corbet original

The 5.15-rc7 kernel prepatch is out, rather
later than would have normally been expected due to Linus’s travel schedule.

But please do give it a good testing to make sure we’ve shaken out
any issues. I have yet more travel coming up next week, so it would
be very convenient for me to delay the merge window if I get the
excuse to do so, but right now that looks unlikely.

[$] Replacing congestion_wait()

Post Syndicated from corbet original

Memory management is a balancing act in a number of ways. The kernel must
balance the needs of current users of memory with anticipated future needs,
for example. The kernel must
also balance the act of reclaiming memory for other uses, which can involve
writing data to permanent storage, with the rate of data that the
underlying storage devices are able to accept. For years, the
memory-management subsystem has used storage-device congestion as a signal
that it should slow down reclaim. Unfortunately, that mechanism, which was
a bit questionable from the beginning, has not worked in a long time. Mel
Gorman is now trying to fix this problem with a
patch set
that moves the kernel away from the idea of waiting on congestion.

[$] Synchronized GPU priority scheduling

Post Syndicated from corbet original

Since the early days, Unix-like systems have implemented the concept of
process priorities, where higher-priority processes are given more
CPU time to get their work done. Implementations have changed, and
alternatives (such as deadline scheduling)
are available for specialized situations, but the core priority (or, in an
inverted sense, “niceness”) concept
remains essentially the same. What should happen, though, in a world where
increasing amounts of computing work is done outside of the CPU? Tvrtko
Ursulin has put together a
patch set
showing how the nice mechanism can be extended to GPUs as

You Can Now Directly Read Data Logs From Tesla Vehicles (Jalopnik)

Post Syndicated from corbet original

The Jalopnik automotive site has posted an
on a
(relatively) new set
of open-source tools
that can extract log data from Tesla cars.

Since Tesla cars run a Debian-based operating system, navigating
through their file systems is somewhat trivial to anyone who’s
spent a weekend messing with virtual Linux machines (or watching
Mr. Robot). Actually accessing the car’s memory, however, is
considerably harder: all cases require at least partially
disassembling the dashboard, and some even require disassembly of
the car’s media control unit.

Once that’s done, however, the data trove is incredible.

Notes from the 2021 Git Contributors’ Summit

Post Syndicated from corbet original

For those who are curious about where the development of Git is headed:
Johannes Schindelin has posted an
extensive set of notes
from the just-concluded Git Contributors’

We held our second all-virtual Summit over the past two days. It was the
traditional unconference style meeting, with topics being proposed and
voted on right before the introduction round. It was really good to see
the human faces behind those email addresses.

32 contributors participated, and we spanned the timezones from PST to

Be sure to go into the thread for the full notes.

[$] Controlling the CPU scheduler with BPF

Post Syndicated from corbet original

While the BPF virtual machine has been supported by Linux for most of
the kernel’s existence, its role for much of that time was limited to, as
its full
name (Berkeley packet filter) would suggest, filtering packets. That began to change in 2012 with the introduction
of seccomp() filtering, and the pace picked up in 2014 with the arrival
of the extended BPF virtual machine. At this point, BPF hooks have found their
way into many kernel subsystems. One area that has remained BPF-free,
though, is the CPU scheduler; that could change if some version of
this patch
from Roman Gushchin finds its way into the mainline.

[$] A disagreement over get_mm_exe_file()

Post Syndicated from corbet original

Differences of opinion over which kernel symbols should be exported to
loadable modules have been anything but uncommon over the years. Often,
these disagreements relate to which kernel capabilities should be available
to proprietary modules. Sometimes, though, it hinges on the disagreements
over the best way to solve a problem. The recent discussion around the
removal of an export for a core kernel function is a case in point.

[$] Possible changes to Debian’s decision-making processes

Post Syndicated from corbet original

The name Debian brings to mind a Linux
distribution, but the Debian project is far more than that; it is an
ongoing experiment in democratic project governance. Debian’s processes
can result in a lot of public squabbling; one should not lose track,
though, of the fact that those processes have enabled a large community to
maintain and grow a complex distribution for decades without the benefit of
an overseeing corporate overlord. Processes can be improved, though; a
recent proposal
from Russ Allbery
gives an interesting picture of where the pain points
are and what can be made better.

[$] A viable solution for Python concurrency

Post Syndicated from corbet original

Concerns over the performance of programs written in Python are often
overstated — for some use cases, at least. But there is no getting around
the problem imposed by the infamous global interpreter lock (GIL), which
severely limits the concurrency of multi-threaded Python code. Various
efforts to remove the GIL have been made
over the years, but none have come anywhere near the point where they would
be considered for inclusion into the CPython interpreter. Now, though, Sam
Gross has entered
the arena
with a proof-of-concept implementation that may solve the
problem for real.

Plasma 25th Anniversary Edition released

Post Syndicated from corbet original

The KDE project is celebrating its 25th anniversary with a special release
of the Plasma desktop.

This time around, Plasma renews its looks and, not only do you get
a new wallpaper, but also a gust of fresh air from an updated
theme: Breeze – Blue Ocean. The new Breeze theme makes KDE apps and
tools not only more attractive, but also easier to use both on the
desktop and your phone and tablet.

Of course, looks are not the only you can expect from Plasma 25AE:
extra speed, increased reliability and new features have also found
their way into the app launcher, the software manager, the Wayland
implementation, and most other Plasma tools and utilities.

Lots of details can be found in the

A study of data collection by Android devices

Post Syndicated from corbet original

A group of researchers at Trinity College in Dublin has released the
results of a study
into the data collected by a number of Android
variants. There are few surprises here, but the picture is still

We find that the Samsung, Xiaomi, Huawei and Realme Android
variants all transmit a substantial volume of data to the OS
developer (i.e. Samsung etc) and to third-party parties that have
pre-installed system apps (including Google, Microsoft, Heytap,
LinkedIn, Facebook). LineageOS sends similar volumes of data to
Google as these proprietary Android variants, but we do not observe
the LineageOS developers themselves collecting data nor
pre-installed system apps other than those of Google. Notably,
/e/OS sends no information to Google or other third parties and
sends essentially no information to the /e/OS developers.

[$] The intersection of modules, GKI, and rocket science

Post Syndicated from corbet original

One does not normally expect a lot of controversy around a patch series
that makes changes to platform-specific configurations and drivers.
The furor over some work on the Samsung Exynos platform may thus be
surprising. When one looks into the discussion, things become more clear;
it mostly has to do with disagreements over the best ways to get hardware
vendors to cooperate with the kernel development community.