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Systems ideas that sound good but almost never work
Some engineering patterns that sound good but almost never work as intended
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The latest blog posts to take off on Hacker News. 569 posts.
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Colliding with the SHA prefix of Linux's initial Git commit
Or, how to break all the tools that parse the "Fixes:" tag Kees Cook There was a recent discussion about how Linux's "Fixes" tag, which ...
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Linux Context Switching Internals: Process State and Memory
How does the Linux kernel represent processes and their state: A breakdown of task_struct and mm_struct
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Why Linux is not ready for the desktop, the final edition
The previous iteration of this article was too technical, too long, and contained a lot of controversial points, so I've been thinking for a long time about rewriting it completely, making it accessible to the non-technical folks, and exposing the deeper core issues that still make Linux a questionable match for the…
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Dumping Memory to Bypass BitLocker on Windows 11
Memory-Dump-UEFI is a UEFI application for dumping the contents of RAM.
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Debugging memory corruption: who the hell writes "2" into my stack? (2016)
Several weeks ago we received a bug report from a customer that said their game was crashing when using IL2CPP scripting backend. QA verified the bug and assigned it to me for fixing. The project was quite big (although far from the largest ones); it took 40 minutes to build on my machine. The instructions on the bug…
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Revisiting the NetBSD Build System
I recently picked up an embedded project in which I needed to build a highly customized full system image with minimal boot times and NetBSD was the best choice for it. Let's look at why its build system helps.
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Execution units are often pipelined
In the context of out-of-order microarchitectures, I was under the impression that execution units remain occupied until the µop they’re processing is complete. This is often not the case.
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The CAP theorem of Clustering: Why Every Algorithm Must Sacrifice Something
No clustering algorithm is perfect and you must make a trade-off.
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A Simple ELF
The Ivory Tower is a blog about software engineering and development philosophy by Anders Sundman.
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Seconds Since the Epoch
This is not at all news, but it comes up often enough that I think there should be a concise explanation of the problem. People, myself included, like to say that POSIX time, also known as Unix time, is the number of seconds since the Unix epoch , which was 1970-01-01 at 00:00:00.
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VPR: Nordic's First RISC-V Processor
VPR (pronounced “Viper”) is Nordic Semiconductor’s first RISC-V processor, landing in the new nRF54H and nRF54L lines of SoCs after their initial announcements in April and October of 2023 respectively. Readers of this blog are familiar with my long-running obsession interest in RISC-V (see my RISC-V Tips and RISC-V…
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Demystifying Debuggers, Part 2: The Anatomy of a Running Program
On the concepts involved in a running program. What happens, exactly, when you double click an executable file, or launch it from the command line, and it begins to execute?
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Will that hub or dock slow your SSDs, or even make them faster?
How to connect a USB4 SSD to get better performance from an Intel Mac. Should you buy a Thunderbolt 4 hub, or a Thunderbolt 5 dock? Do any of these live ‘up to’ their claimed performanc…
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When power cycling your (x86) server isn't enough to recover it
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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How bloom filters made SQLite 10x faster
This is the fascinating story of how researchers used Bloom filters cleverly to make SQLite 10x faster for analytical queries. These are my five-minute notes on the paper SQLite: Past, Present, and Future
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Introducing S2
Introducing S2, a serverless stream store that makes durable real-time streams feel as simple and scalable as object storage.
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The RAM Myth
The RAM myth is a belief that modern computer memory resembles perfect random-access memory. Cache is seen as an optimization for small data: if it fits in L2, it’s going to be processed faster; if it doesn’t, there’s nothing we can do. Most likely, you believe that code like this is the fastest way to shard data (I’m…
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How concurrency works: A visual guide
Welcome to Waqas' blog
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Running NetBSD on IBM ThinkPad 380Z
Launched in 1998, the 380Z was one very fine ThinkPad. It was the last ThinkPad to come in the classic bulky and rectangular form factor. It was also one of the first to feature a huge 13.3" TFT display, powerful 233MHz Pentium II, and whopping 160 megs of RAM.
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In Search of a Faster SQLite
Researchers at the University of Helsinki and Cambridge attempted to build a faster SQLite using modern programming paradigms like io_uring and disaggregated storage. They demonstrate up to a 100x reduction in tail latency. These are my notes.
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Load is not what you should balance: Introducing Prequal
Bartek Wydrowski, Google Research; Robert Kleinberg, Google Research and Cornell; Stephen M. Rumble, Google (YouTube); Aaron Archer, Google Research
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Fast LLM Inference From Scratch (using CUDA)
This post is about building an LLM inference engine using C++ and CUDA from scratch without libraries.
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A quick look at OS/2's builtin virtualization
A while ago, someone on the fediverse mentioned "OS/2's virtualization features" to me. I don't remember who it was, sorry. I had the chance to take a look at this today.
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macOS 15.2 breaks the ability to copy the OS to another drive
macOS 15.2 was released a few days ago, with a surprise. A terrible, awful surprise.
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Elixir/Erlang Hot Swapping Code (2016)
Hot code reloading with Elixir and Erlang
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Making memcpy(NULL, NULL, 0) well-defined
C2y makes memcpy(NULL, NULL, 0) and other zero-length operations on null pointers well defined. This removes a source of bugs that may result in security issues.