Description
Join us to discuss topics related to LLVM and building the Linux kernel.
Significant progress was made in 2019 and 2020 as Clang gained the ability to compile multiple different architectures supported by the kernel. Many LLVM utilities also now work for assembling and linking the kernel as well. Multiple continuous integration services covering the kernel are also building with Clang. Android kernels and ChromeOS kernels are now built with Clang; OpenMandriva and Google's production kernel are testing Clang built kernels.
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Behan Webster (Converse in Code Inc.), Nick Desaulniers (Google)27/08/2020, 07:00
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Will Deacon, Peter Zijlstra (Intel OTC), Paul McKenney (Facebook)27/08/2020, 07:05
For better or worse, the Linux kernel relies heavily on hardware ordering guarantees concerning dependencies between memory access instructions as a way to provide efficient, portable implementations of concurrent algorithms. In spite of the lack of C language support, preserving source-level dependencies through to the generated CPU instructions is achieved through a delicate balance of...
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John Baublitz, Nick Desaulniers (Google), Alex Gaynor, Geoffrey Thomas, Josh Triplett, Miguel Ojeda27/08/2020, 07:35
What would it take to have in-tree support for writing kernel code in Rust? What should Kbuild integration look like? What APIs should be the initial priorities to expose in Rust? Let's figure out if any other other questions remain (e.g., can we safely link against GCC-built kernels, and do we need to) about how to get in-tree support for Rust.
Rust is a systems programming language that...
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Sami Tolvanen (Google), Bill Wendling (Google), Nick Desaulniers (Google)27/08/2020, 08:05
Newer compiler optimization techniques stand to improve the runtime performance of Linux kernels. These techniques analyze more of a program (Link Time Optimization aka "LTO") or make use of profiling information to improve code layout (Profile Guided Optimization "PGO" and Automatic Feedback Directed Optimization "AutoFDO"). Now that Google is shipping all three in various kernel...
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Nathan Huckleberry, Nathan Chancellor27/08/2020, 08:50
In this talk we will discuss clang-built kernel compile times, current
work to improve compiler performance and recommendations to reduce
build times regardless of toolchain.We will present our findings alongside several metrics of compiler
performance, including:- Comparative timing breakdowns between toolchains
- Linux perf profiling on clang builds of the kernel
- Perfetto...
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Nathan Huckleberry, Miguel Ojeda27/08/2020, 09:10
Clang is a production C compiler (part of LLVM) that provides APIs for
C code parsing, formatting, custom compiler warnings, static analysis, etc. This framework has spawned widely used tools like clang-format and clang-tidy. These tools can be easily tailored for particular codebases like the Linux kernel.This talk shows how to run clang-format, clang-tidy (including writing custom...
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Bill Wendling (Google)27/08/2020, 09:30
"Asm goto with outputs" is a clang extension of the GNU "asm goto" feature. As the name implies, it allows asm goto to have outputs on the default branch (outputs on indirect branches aren't supported). In this talk, we discuss the benefits of this feature, its implementation and design limits, and how the clang and gcc communities can work together on future GNU C extensions.
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Prof. Mathieu Acher (University of Rennes 1)27/08/2020, 10:00
The Linux kernel offers more than ten thousands configuration options that can be combined to build an almost infinite number of kernel variants. Developers and contributors spend significant effort and computational resources to continuously track and hopefully fix configurations that lead to build failures. In this talk, we report on our endeavor to develop an infrastructure, called TuxML,...
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Dan Rue, Antonio Terceiro (Linaro)27/08/2020, 10:15
Reproducing build errors reported to a mailing list is a pain. How much time do
we collectively spending asking "What kernel config did you use?", "What
compiler?" and "What architecture?"?What if we could version and distribute build environments similarly to how we
version Linux source code?TuxMake is a tool that provides portable and repeatable Linux kernel builds
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across a... -
Nick Desaulniers (Google)27/08/2020, 10:30
Multiple CI efforts to provide coverage of the Linux kernel are now building and providing results of builds with Clang (KernelCI, 0day bot, Linaro toolchain team and tuxbuild team, Clang Built Linux). Let's all meet to discuss what's working, what can be improved, the current status of builds of various architectures, and what the future direction of testing the various LLVM utilities might...
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