Why the thread-pool math matters: a busy-wait locks one OS thread per waiting actor. A semaphore lets thousands of sleeping actors share a handful of threads.

Continuing on from S1E1 that highlighted issues around memory access stalls, and optimisation of hot and cold data, the same issue shows up with nested loops — when we traverse a data structure larger than the cache in t

Not all memory is equal. It's a beginner's mistake to think that all memory access takes an equal amount of time. Many managed languages abstract memory layout away so the programmer can focus on functionality, but in do

In all programming environments it is important to have a single source of truth, particularly when it comes to constants and environment variables: if you want to change a variable and forgetting to update every instanc

Another snippet, this time to batch rename the extension of a set of files to another, in my case I needed to rename .html files as .mustache so, as before, (when I set up a scripts folder in my user folder and added it

Similar to the previous post, I can never remember the correct format for grepping recursively through folders for a particular string. So I added the following script to a file called findinfiles in the scripts director

I can never remember the correct format of the find command so that I can recusively search through folders for a particular file or files. So I set up a scripts folder in my user folder and added it to my path in my .ba

Most of my websites run on Amazon's EC2 servers and in setting up a new one today I thought I had better come up with a better backup strategy. In the past I've just asked EC2 to create either AMI or EBS snapshots, but t

The built in Android browser for versions 4.something onwards have an annoying little feature called auto-fit turned on automatically. What this does is fix the width of the primary text column to be as wide as the devic

I needed to strip out some DOM nodes from a HTML file. I would use SED but some of the tags are multiline, and SED/regexes really don't understand HTML/XML and get really confused if you're using nested tags of the same

I recently made some changes to my /etc/X11/xorg.conf file which backfired and Ubuntu (12.10 in this case) would crash while loading the operating system. It should be simple enough to undo the last change you made to a

If you ever need to redirect one domain name to another (using apache) and you need to do it in code you can simply create a .htacess file in the root of the folder that needs to be redirected and pop the standard 301 re

If you're ever sat at the linux commandline and had a repetitive task to complete on some files or directories then you'll find "xargs" together with "find" a very useful combination. Find will return a list of files and

Today I've been parsing some text files in Visual Studio 2010 express in a semi-manual kind of way (lots of Find and Replace commands!). They were generally not too bad but I needed to clean them up to bring them into a

I run different google calendars for different organisations, and many of them have regular repeating meetings in the calendar. It is relatively easy to set up repeating meetings in a google calendar but unfortunately th

What data matt-helps.com collects and how it's used.

If ctrl-c isn't interrupting the foreground program in your terminal, the most common cause is that the terminal has rebound ctrl-c to "copy to clipboard" unconditionally. The fix is to go into the terminal's keyboard sh

I have used Amazon Elastic Cloud (EC2) for my dedicated hosting needs for nearly 6 months now. They've just released a new "bulk-buy" service that enables you to buy 1 or 3 years' of as many instances as you want in adva

Spotify is a great application that lets you listen to any music they have (there's an incredible amount on there) with the odd, almost unnoticable, advert thrown in to pay for the service. It works on windows or mac, bu

Just had to make a few changes to a website I own that means changing the same text in lots of files. Linux has a lot of powerful tools to do this across many directories in one go. The safe modern pattern is: Two comman

In linux if you have a laptop with a trackpad just below the keyboard, sometimes while typing you'll brush the pad and the cursor jumps — you stop typing, put the cursor back, repeat. Sensitive touchpads make this even w

One of the things you can do to speed up browsing and general internet activity is to create a local DNS cache. A DNS is a Domain Name Server and its purpose is to convert domain names to IP addresses. Every time you typ

Alien is a nice little linux utility that converts .rpm software packages to .deb packages so that you can install software packaged for Red Hat on Debian and Ubuntu, etc. Clever. But for those of us on the lpia architec

One of the most powerful/dangerous commands in linux is the "rm" command. It removes the file from the filesystem and whilst with some media formats it is possible to recover an rm'd file in ext3 it is almost impossible

My laptop is now bricked. Apparently it is an LCD failure. It took me forever to find out what the flashing lights on my dell laptop meant as the docs seem to be missing from dell's support site. In order to make the lap

Having moved house I have just been connected to broadband. The connection is a decent enough 4mbps but for some reason, especially in the evening, when I went to a website when I was surfing the browser would spend a fe

Following on from my previous article, <a href="2008-06-23=firefox3eastereggsaboutmozilla" target="blank"Firefox 3 Easter Eggs</a, I have discovered that broadband users can get a significant speed increase from Firefox

There are some moderately amusing Easter Eggs in Firefox 3. Simply type one of the following into the address bar (no spaces or http) and you'll get a message: (ok, technically "about: config" isn't an Easter Egg, but th

Sometimes you just have to move your website. Perhaps you were hosting a website in a subdirectory of another site and it became popular? Perhaps you need to move to another website hosting company? The reasons are many