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Bcachefs, an Introduction/Exploration
Introduction & background information NOTE: This content is from an internal talk I gave, thus the reason it may read like a presentation So what is …
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The latest blog posts to take off on Hacker News. 569 posts.
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How to build highly-debuggable C++ binaries
code { white-space : pre-wrap !important; } This article is tightly scoped to cover one topic with specific, actionable advice: How to configure...
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Let's consign CAP to the cabinet of curiosities
Brewer’s CAP theorem, and Gilbert and Lynch’s formalization of it , is the first introduction to hard trade-offs for many distributed systems engineers. Going by the vast amounts of ink and bile spent on the topic, it is not unreasonable for new folks to conclude that it’s an important, foundational, idea.
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Hiding Linux Processes with Bind Mounts
Lately I’ve been thinking about Stephan Berger’s recent blog post on hiding Linux processes with bind mounts. Bottom line here is that if you have an evil process you want to hide, use …
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"Doors" in Solaris: Lightweight RPC Using File Descriptors (1996)
A door is a "file" descriptor used to describe a procedure in a process and optionally some additional state associated with the procedure. Doors were initially designed as Spring object descriptors used to encapsulate the state and capabilities of C++ objects. A process which obtains a door is free to pass it, along…
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Rediscovering Transaction Processing from History and First Principles
In July 2020, I stumbled into a fundamental limitation in the general-purpose database design for transaction processing.
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Counting bytes faster than you'd think possible
“Summing ASCII Encoded Integers on Haswell at the Speed of memcpy” turned out more popular than I expected, which inspired me to take on another challenge on HighLoad: Counting uint8s . I’m currently only #13 on the leaderboard, ~7% behind #1, but I have already learned some interesting things. In this post I’ll…
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The Linux audio stack demystified (and more)
Digital audio processing is a complex yet fascinating subject. Getting a deeper understanding requires knowledge in multiple technical disciplines, including physics, electrical/electronical engineering, and some software engineering when it comes to parts of the Linux ecosystem. This article aims to demystify the…
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An interactive guide to x86-64 assembly – moving data
This is the second part of a series of interactive articles on the x86-64 architecture. This part will focus on the first assembly instructions, visualizing the way data moves in memory when they are executed.
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Stremio OS Is Now Available for Raspberry Pi 5 and 4
We are happy to announce that Stremio is now available for Raspberry Pi 5 and 4, installable on an SD card (of at least 8GB). Note: While the Raspberry Pi 5 is fully capable of smooth 4K playback, Raspberry Pi 4 will not be able to play 4K content due to hardware limitations. This release...
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A brief history of Dell Unix (2008)
[update December 2021: files for 86Box install at update December 2020: Dell Unix on 86Box “Today let me present Dell Unix more properly, with 1024×768, 256 colors video and proper networking…
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Prometheus metrics saves us from painful kernel debugging (2022)
You're probably reading this page because you've attempted to access some part of my blog (Wandering Thoughts) or CSpace , the wiki thing it's part of. Unfortunately you're using a browser version that my anti-crawler precautions consider suspicious, most often because it's too old (most often this applies to versions…
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Instrumenting Python GIL with eBPF
Learn how to measure the impact of Python GIL contention on application latency using eBPF, with real workload examples.
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Building the new hypermedia systems
A shiny new edition of Hypermedia Systems is out! Apart from incorporating typo and grammar fixes sent in by readers, the book was completely redesigned inside with a new layout. To achieve a much higher fidelity of design, we ported the book to Typst --- the hot new LaTeX replacement.
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NVIDIA Transitions Fully Towards Open-Source Linux GPU Kernel Modules
With the R515 driver, NVIDIA released a set of Linux GPU kernel modules in May 2022 as open source with dual GPL and MIT licensing. The initial release targeted datacenter compute GPUs…
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NSCopyObject, the griefer that keeps on griefing
NSCopyObject is a very old Foundation function – pre-dating Mac OS X entirely; from the NeXT era – that was originally basically just memcpy , but now it’s complicated. A lot more complicated.
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A Review of Linux on Surface Pro 4
I bought a Surface Pro 4 in 2016. It has an Intel Core m3-6Y30 CPU and 4GB memory. The spec is not that impressive even compared to an average laptop released years earlier. On the other hand, the form factor is very attractive to me: at a very low price, you get a tablet with a beautiful HiDPI 2k screen, a pressure…
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The six dumbest ideas in computer security (2005)
There's lots of innovation going on in security - we're inundated with a steady stream of new stuff and it all sounds like it works just great. Every couple of months I'm invited to a new computer security conference, or I'm asked to write a foreword for a new computer security book. And, thanks to the fact that it's…
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How we sped up Notion in the browser with WASM SQLite
Notion engineers sped up Notion's browser speed with WASM SQLite
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Beating the Compiler
In modern times, everyone knows that writing assembly is a fool's errand: compilers are the result of literal engineer-centuries of work, and they know the processor much better than you do.
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Summing ASCII encoded integers on Haswell at almost the speed of memcpy
“Print the sum of 50 million ASCII-encoded integers uniformly sampled from [0, 2³¹−1], separated by a single new line and sent to standard input.”
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Beating the L1 cache with value speculation (2021)
If we have a heuristic to guess some value cheaply, we can remove a data dependency in a tight loop using the branch predictor. This allows the CPU to run more instructions in parallel, increasing performance. If this explanation does not make much sense to you, keep reading to learn about some of the magic making…
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FlashAttention-3: Fast and Accurate Attention with Asynchrony and Low-Precision
FlashAttention-3 achieves up to 75% GPU utilization on H100s, making AI models up to 2x faster and enabling efficient processing of longer text inputs. It allows for faster training and inference of LLMs, supports lower precision operations for improved efficiency.
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Iconography of the X Window System: The Boot Stipple
If you are of a certain vintage, this image is burned indelibly somewhere in your posterior parietal complex: Oh, my old friend. How it’s been a long time. Cultural Significance For the uninitiated, what are we looking at? Could it be the Moiré Error from Doom? Well, no. You are looking at (part of) the boot up screen…
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Things I learned while writing an x86 emulator (2023)
If you’ve read my first post about assembly language, you might expect that this is another post on how to understand assembly language. I will write more about that at some point, but this post is not that. Instead, this post is going to talk about some of the weird things and random trivia I learned while writing an…
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End-to-end congestion control cannot avoid latency spikes (2022)
What are the fundamental limits of end-to-end congestion control in 5G networks?
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The Race to Seal Helium HDDs (2021)
Long thought impossible, helium has been one of the greatest breakthroughs for high-capacity HDDs. This is the story the science behind them.
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