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Linux Observability with BPF
Why BPF and XDP are something you should learn.
New
The latest blog posts to take off on Hacker News. 4,389 posts.
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Raspberry Pi microSD card performance comparison
Note: I also posted a separate review of some A2 'Application Performance' class cards, see this post: A2-class microSD cards offer no better performance for the Raspberry Pi. As a part-time tinkerer and full-time developer, I have been fascinated by single board computers (SBCs) since the first Raspberry Pi was…
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PCI Express on the Raspberry Pi 4
After the daily dose of Hackaday - and with an idea that seemed very doable, and actually, with some improvements can be easily reproducible.
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So you think you know C? (2016)
It's a C test. If you think you know C, take this test. It only has 5 questions.
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FreeBSD – A lesson in poor defaults
This page lists some of the changes I make to a vanilla install of FreeBSD for security hardening. Some changes to increase network performance or make things a bit more sane are also included. It only covers basic changes that a sysadmin can make to a running system.
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The Day “/Proc” Died
Solaris'd... This morning I got an email from our group manager asking about a UNIX server...
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It’s Time for a Modern Synthesis Kernel
I had a student (Fred Smith) who worked on extensions to Popcorn (the predecessor to Cyclone) that supported run-time code generation in a lightweight fashion. Here’s a paper describing part of the system: https://ecommons.cornell.edu/handle/1813/5812 . Fred’s thesis had a bunch more.
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Mistakes we made adopting event sourcing and how we recovered
Good judgement is the result of experience ... Experience is the result of bad judgement. — Fred Brooks
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Network Transparency with Wayland
M. Stoeckl's website
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NetBSD on the last G4 Mac mini and making the kernel power failure proof
(First, as a public service message, if you're running Linux on a G5 you may wish to update the kernel .) I'm a big fan of NetBSD . I've ru...
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Machine learning systems are stuck in a rut
Machine learning systems are stuck in a rut Barham & Isard, HotOS’19 In this paper we argue that systems for numerical computing are stuck in a local basin of performance and programmabil…
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Avoid Indirection in Code
I often see code where authors abstract away details by placing them in some external function. Here is a toy example:
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PulseAudio Under the Hood (2017)
I’m working on the Roc Toolkit open-source project, a development kit for realtime audio streaming over the network. You can read more about the project in these two articles: 1, 2. We decided to implement a set of PulseAudio modules that will allow PulseAudio to use Roc as a network transport. Many Linux distros…
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FPGAs Have the Wrong Abstraction for Computing
Verilog is the de facto abstraction for programming today’s FPGAs. RTL programming is fine if you want to use FPGAs for their traditional purpose as circuit emulators, but it’s not the right thing for the new view of FPGAs as general-purpose computational accelerators.
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Avoiding Instruction Cache Misses
Excessive instruction cache misses are the kind of a performance problem that's going to appear only in larger codebases. In this article, I'm describing some ideas on how to deal with this issue.
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Learning to Build Distributed Systems
A common question I get at work is “how do I learn to build big distributed systems?”. I’ve written replies to that many times. Here’s my latest attempt.
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You are not Google. You are not Netflix
You are also not Spotify, Amazon, Apple, Microsoft, Facebook or one of several other big tech companies I could mention here. If I have excluded anybody reading this - I am sorry.Maybe you will still enjoy the read. For everyone else: This article is probably for you. To give you...
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Debian Riscv64 port in mid 2019
It's been a while since last post (Talk about the Debian GNU/Linux riscv64 port at RISC-V workshop), and sometimes things look very quiet from outside even if the people on the backstage never stop working. So this is an update on the status of this port before the release of buster, which should happen in a few weeks…
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The world in which IPv6 was a good design (2017)
Last November I went to an IETF meeting for the first time. The IETF is an interesting place; it seems to be about 1/3 maintenance grunt wo...
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Performance Speed Limits
A laundry list of speed limits that your code can’t exceed.
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Rethinking the filesystem as global mutable state, the root of all evil
When you invoke a function in an imperative programming language, you pass arguments to that function. But that function may also operate on global mutable state, meaning there are other factors in the operation of that function than merely the arguments you pass to it. To some extent this kind of contextual, implicit…
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Unicode programming, with examples in C
Most programming languages evolved awkwardly during the transition from ASCII to 16-bit UCS-2 to full Unicode. They contain internationalization features that often aren’t portable or don’t suffice.
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Malloc Never Fails (2012)
Here’s a fun bit of trivia: malloc on Linux never fails [due to the obvious cause]. In this post, we’ll show that this indeed is the case, and explore why…
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Emulator basics: a stack and register machine
Writing an x86 emulator from scratch in JavaScript: 1. a stack and register machine
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State of Industrial Control Systems in Poland and Switzerland
TL;DR New update for Kamerka allows to map Industrial Control Systems of whole country. As in previous version, interactive map is created…
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Battle testing data integrity verification with ZFS and Btrfs
In this article I share the results of a home-lab experiment in which I threw some different problems at ZFS, Btrfs and mdadm+dm-integrity in a RAID-5 setup.