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Igniting the GPU: From Kernel Plumbing to 3D Rendering on RISC-V
How I enabled the PowerVR GPU on the TH1520 SoC by writing the missing kernel drivers.
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A production bug that made me care about undefined behavior
Years ago, I maintained a big C++ codebase at my day job. This product was the bread winner for the company and offered a public HTTP API for online payments. We are talking billions of euros of processed payments a year.
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Static Allocation with Zig
Introducing kv, a statically allocated key/value server.
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Huge Binaries
A problem I experienced when pursuing my PhD and submitting academic articles was that I had built solutions to problems that required dramatic scale to be effective and worthwhile. Responses to my publication submissions often claimed such problems did not exist; however, I had observed them during my time within…
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Last Year on My Mac: Look Back in Disbelief
If someone had told me 12 months ago what was going to happen this past year, I wouldn’t have believed them. Skipping swiftly past all the political, economic and social turmoil, I come to th…
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Functional programming and reliability: ADTs, safety, critical infrastructure
> In banking, telecom, and payments, reliability is not a nice to have. It is table stakes. The most reliable systems I have worked on reduce entire classes of bugs before the code even runs. Function...
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Why is calling my asm function from Rust slower than calling it from C?
This is a follow-up to making the rav1d video decoder 1% faster, where we compared profiler snapshots of rav1d (the Rust implementation) and dav1d (the C …
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Unix "find" expressions compiled to bytecode
In preparation for a future project, I was thinking about at the unix find utility . It operates a file system hierarchies, with basic operations selected and filtered using a specialized expression language. Users compose operations using unary and binary operators, grouping with parentheses for precedence. find may…
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Asahi Linux with Sway on the MacBook Air M2 (2024)
I bought a MacBook Air M2. As of writing, it's very affordable with the 16 GB RAM, 256 GB SSD, 13.6" model available for $750. As of writing, also Asahi Linux doesn't support anything newer than M2.
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When compilers surprise you
Sometimes compilers can surprise and delight even a jaded old engineer like me
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Clock synchronization is a nightmare
Time seems simple. But we engineers lose sleep over something as basic as keeping clocks in sync. Here’s why…
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Big GPUs don't need big PCs
Ever since I got AMD, Intel, and Nvidia graphics cards to run on a Raspberry Pi, I had a nagging question: What's the point? The Raspberry Pi only has 1 lane of PCIe Gen 3 bandwidth available for a connection to an eGPU. That's not much. Especially considering a modern desktop has at least one slot with 16 lanes of…
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What Does a Database for SSDs Look Like?
What does a relational database designed specifically for local SSDs look like? Postgres, MySQL, SQLite and many others were invented in the 90s and 00s, the era of spinning disks. A local NVMe SSD has ~1000x improvement in both throughput and latency. Design decisions like write-ahead logs, large page sizes, and…
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The Polyglot NixOS
Recently a colleague mentioned building NixOS images that run unchanged on multiple architectures. Given the past adventures on this blog with systemd-repart and cross-compiling NixOS, I decide to give this a go.
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Getting bitten by Intel's poor naming schemes
Don't you love misleading documentation?
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Vm.overcommit_memory=2 is the right setting for servers
The Linux kernel has a feature where you can tune the behavior of memory allocations: the vm.overcommit_memory sysctl. When overcommit is enabled (sadly, this is the default), the kernel will typically return a mapping when brk(2) or mmap(2) is called to increase a program’s heap size, regardless of whether or not…
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TLA+ Modeling Tips
Model minimalistically Start from a tiny core, and always keep a working model as you extend. Your default should be omission. Add a compone...
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Problems with D-Bus on the Linux desktop
A programming blog written by Vaxry.
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Full Unicode Search at 50× ICU Speed with AVX‑512
ICU gets Unicode right and pays for it. This post shows a different approach: fold-safe windows, SIMD probes, and verifiers for fast UTF‑8 search.
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Fuzix on a Raspberry Pi Pico
Because your $5 microcontroller needed to run UNIX
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Closures as Win32 Window Procedures
Back in 2017 I wrote about a technique for creating closures in C using JIT-compiled wrapper. It’s neat, though rarely necessary in real programs, so I don’t think about it often. I applied it to qsort , which sadly accepts no context pointer. More practical would be working around insufficient custom allocator…
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Linux CVEs, more than you ever wanted to know
It’s been almost 2 full years since Linux became a CNA (Certificate Numbering Authority) which meant that we (i.e. the kernel.org community) are now responsible for issuing all CVEs for the Linux kernel. During this time, we’ve become one of the largest creators of CVEs by quantity, going from nothing to number 3 in…
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The stack circuitry of the Intel 8087 floating point chip, reverse-engineered
Early microprocessors were very slow when operating with floating-point numbers. But in 1980, Intel introduced the 8087 floating-point copro...
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From Azure Functions to FreeBSD
Putting FreeBSD’s “power to serve” motto to the test. On Thanksgiving morning, I woke up to one of my web services being unavailable. All HTTP requests failed with a “503 Service unavailable” error. I logged into the console, saw a simplistic “Runtime version: Error” message, and was not able to diagnose the problem…
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The Anatomy of a macOS App
How Mac applications evolved from a multitude of resources to a bundle formed from a standard layout of directories, and how they have come to be largely self-contained in macOS 26.
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Booting Linux in QEMU and Writing PID 1 in Go to Illustrate Kernel as Program
Most books and courses introduce Linux through shell commands, leaving the kernel as a mysterious black box doing magic behind the scenes. In this post, we will run some experiments to demystify it: the Linux kernel is just a binary that you can build and run.
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Golang's big miss on memory arenas
When your software team needs to pick a language today, you typically weigh two factors: language performance and developer velocity.
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You can't fool the optimizer
Pattern recognition can see through obfuscated code to find the right instruction
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100k TPS over a billion rows: the unreasonable effectiveness of SQLite
A blog mostly about Clojure programming