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A bug story: data alignment on x86
This sounds unusual. Who ever wants to do this in real life? Normally, we only see code like this as primary school assignments or compiler benchmarks. However, this time it happened in real life.
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Introduction to strace
There will come a time when you will find yourself asking “What the heck is that process doing?”. To uncover the mysteries behind the behaviour of a process, we have a tool called strace .
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A Unix Utility to Know About: lsof (2009)
This is the third post in the article series about Unix and Linux utilities that you should know about. In this post I will take you through the useful lsof tool. If netcat was called the Swiss Army Knife of Network Connections, then I'd call lsof the Swiss Army Knife of Unix debugging. Lsof follows Unix philosophy...
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Systems Past: software innovations we actually use (2014)
Note: This is a position piece, not a technical article. Hat tip to Jake Skelcy for requesting such a piece. Computers didn’t always have operating …
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Things I Hate About PostgreSQL (2013)
PostgreSQL Talk
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Visualising the .NET Garbage Collector
As part of an ongoing attempt to learn more about how a real-life Garbage Collector (GC) works (see part 1) and after being inspired by Julia Evans’ excellent post gzip + poetry = awesome I spent a some time writing a tool to enable a live visualisation of the .NET GC in action.
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Fast Servers
There's a network-server programming pattern which is so popular that it's the canonical approach towards writing network servers:
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The Error Model in Midori
Joe Duffy's Blog | Adventures in the high-tech underbelly
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Throughput vs. Latency and Lock-Free vs. Wait-Free
On the previous post we showed an excellent presentation by Cliff Click, and one of the things he mentions is that there is performance for ...
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The surprising cleverness of modern compilers
I wanted to know how a modern C compiler like clang would process the following C code: #include <stdint.h> int count(uint64_t x) { int v = 0; while(x != 0) { x &= x - 1; v++; } return v; } Can you guess? popcntq %rdi, %rax That is right. A fairly sophisticated C function, … Continue reading The surprising cleverness…
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Why is .NET reflection slow?
It’s common knowledge that reflection in .NET is slow, but why is that the case? This post aims to figure that out by looking at what reflection does under-the-hood.
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The State of Linux Security
This is the state of Linux security. With the most important updates around Linux and open source security. From conferences to self-protection.
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Beating the Compiler
An oft-repeated fact on programming forums these days is that a decent optimizing compiler will always beat a puny human's attempt at hand-written assembler. There are rare cases, like MPEG decoders, where making good use of the SIMD instructions can allow assembly to massively beat the compiler. But generally you'll…
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Compiler Bugs Found When Porting Chromium to VC++ 2015
Moving a big software project to a new compiler can be a lot of work, and few projects are bigger than Chromium. In addition to the main Chromium repository, which includes all of Blink, there are …
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Laws of Performant Software
Learning how to write performant code is hard. Here are a few simple laws that I hope will convey the core of the matter. I’m calling them…
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FreeBSD Jails the hard way
There are many great options for managing FreeBSD Jails. iocage, warden and ez-jail aim to streamline the process and make it quick an easy to get going. But sometimes the tools built right into the OS are overlooked.
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SELinux is beyond saving
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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C++11 threads, affinity and hyperthreading
For decades, the C and C++ standards treated multi-threading and concurrency as something existing outside the standard sphere - in that "target-dependent" world of shades which the "abstract machine" targeted by the standards doesn't cover. The immediate, cold-blooded replies of "C++ doesn't know what a thread is" in…
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The One Second Dash
The Amazon Dash is a $5 WiFi button that summons a truck to deliver you water or other stuff. Want your Dash to do something else? The popular approach is to sniff its ARP requests. This requires that Dash connect to your network, putting you perilously close to having some DUDE delivered with your IoT mood lighting.
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.NET Core Is Boiling the Ocean
Do they know what the hell they're doing?
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Optimization story: Switching from GMP to gcc's __int128 reduced run time by 95%
A flash of intuition while trying to find a way to lend brian d foy a hand in his search for excellent numbers helped me reduce run time by 95 percent.
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ODROID-C2 Compared to Raspberry Pi 3 and Orange Pi Plus
tl;dr: The ODROID-C2 is a very solid competitor to the Raspberry Pi model 3 B, and is anywhere from 2-10x faster than the Pi 3, depending on the operation. The software and community support is nowhere near what you get with the Raspberry Pi, but it's the best I've seen of all the Raspberry Pi clones I've tried. The…
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Jepsen: Crate 0.54.9 version divergence
In the last Jepsen analysis, we saw that RethinkDB 2.2.3 could encounter spectacular failure modes due to cluster reconfiguration during a partition. In this analysis, we’ll talk about Crate, and find out just how many versions a row’s version identifies.