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Systemd: The Biggest Myths
Posts and writings by Lennart Poettering
Top posts
Every blog post that took off on Hacker News, ranked by the votes of its best submission. 4,390 posts.
3182
Co-routines as an alternative to state machines (2009)
When you have to traverse some sort of a nested data structure (say, a binary tree), one approach is to create a stack that remembers where in the tree you are. Another, much more elegant approach, is to write the function recursively. A recursive function employs the machine stack used to implicitly implement…
3183
The surprising struggle to get a Unix Epoch time from a UTC string in C or C++
So how hard could it be. As input we have something like Fri, 17 Jan 2025 06:07:07 in UTC, and we’d like to turn this into 1737094027, the notional (but not actual) number of seconds that have passed since 1970-01-01 00:00:00 UTC. Trying to figure this out led me to discover many ‘surprise features’ and otherwise…
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Raspberry Pi holds its own against low-cost ARM NAS
Earlier this year, I pitted the $549 ASUSTOR Lockerstor 4 NAS against a homebrew $350 Raspberry Pi CM4 NAS, and came to the (rather obvious) conclusion that the Lockerstor was better in almost every regard. Well, ASUSTOR introduced a new lower-cost NAS, the $329 Drivestor 4 Pro (model AS3304T—pictured above), and sent…
3187
The Four Month Bug: JVM statistics cause garbage collection pauses
TL;DR: The JVM by default exports statistics by mmap -ing a file in /tmp (hsperfdata). On Linux, modifying a memory mapped file can block until disk I/O completes, which can be hundreds of milliseconds. Since the JVM modifies these statistics during garbage collection and safepoints, this causes pauses that are…
3188
How Does a C Debugger Work? (2014)
Debugging, GNU± Linux and WebHosting and ... and ...
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Lockfree Algorithms (2010)
Seru88 adalah situs iGaming resmi dengan sistem RNG transparan, pilihan permainan lengkap, akses mobile dan desktop, serta layanan pelanggan 24/7.
3191
Microcode in Intel's 8087 floating-point chip: the scale instruction
In the 1970s, floating-point arithmetic was a mess. Computer manufacturers had a dozen incompatible arithmetic standards. Moreover, floating...
3192
MySQL now shows its thread names at OS level for better troubleshooting
Starting from v8.0.27, the MySQL daemon shows its thread names at the OS level too, for better troubleshooting. The MySQL 8.0.27 release notes say this: To assist monitoring and troubleshooting, the Performance Schema instrumentation is now used to export names of instrumented threads to the operating system. This…
3193
Linux latency measurements and compositor tuning
Linux latency on the desktop and in games compared to Windows. Network streaming with Sunshine and Moonlight. Tuning the KWin compositor for lower latencies.
3194
Measuring the overhead of WebAssembly using libsodium
The libsodium cryptographic library added support for WebAssembly back in 2017.
3195
Why is the first C++ (m)allocation always 72 KB?
Why is my first C++ (m)allocation always 72 KB?? It’s the ’emergency pool’ for exceptions, here’s how I uncovered it using GDB and digging through the source code of libstdc++, glibc and Valgrind!
3196
Further hardening glibc malloc() against single byte overflows
Introduction Back in 2014, while at Project Zero, I exploited a buffer overflow of a single NUL byte in glibc . Tavis Ormandy had found th...
3197
How to DOS a developer
So you think your favourite FOSS project is moving too fast? Easy, just DOS the developers. Here's a few tips on how to achieve this: On IR...
3198
On the joy of podman and auto-updates (2022)
podman provides an integrated auto-update mechanism, which I recently applied to all of my containers running on feldspaten. The mechanism is nice, but at first appears a bit counter-intuitive. In this post ’m trying to explain how you can use the mechanism and what to watch out for. I’ll start with the trap I think…
3199
4000x Speedup in Reinforcement Learning with Jax
Web publication for "PureJaxRL"
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IPv4 route lookup on Linux
Linux uses an LPC-trie for looking up routes. It provides good performance with low memory use even with millions of routes.
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Distributed systems for fun and profit
git , Single page HTML , Kindle .mobi , PDF , .epub , HTML for printing , book cover .
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Why is my tcp not reliable? (2009)
This post is about an obscure corner of TCP network programming, a corner where almost everybody doesn’t quite get what is going on. I used to think I understood it, but found out last week that I didn’t.
3203
Fast Lossless Color Image Compression
In the research field of compression, the usual goal is to achieve the best possible compression rate. The best known algorithms, however, are very slow, and sometimes impractical for real-world ap…
3204
Adventures in JIT compilation: Part 1 – an interpreter
This is the first post in a series about JIT compilers. The plan is to take a simple input language and develop some interpreters and JITs for it, in roughtly increasing degree of complexity. It's my hope that by the end of the series readers will have a good understanding of what it takes to develop a JIT compiler…
3205
Optimizing Nginx TLS Time To First Byte
TLS is not slow, it's unoptimized. A hands-on tour of optimizing nginx to deliver one-RTT Time To First Byte (TTFB) with TLS.
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Write hybrid CPU/GPU programs in Haskell
What’s better than programming a GPU with a high-level, Haskell-embedded DSL (domain-specific-language)? Well, perhaps writing portab...
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Why ZFS is not good at growing and reshaping pools, or shrinking them
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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File transfers via the parallel port on DOS using LapLink
Fun with LapLink 5 and parallel port file transfers under FreeDOS
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The compiler flag that time forgot
I’m often surprised how long software can keep trying to use compatibility features ages after their best-by date. Now that GCC 4.8 builds on Tige...