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Showing posts from April, 2012

This Blog Has Moved!

Right, so yes, five years ago I moved to github pages, and never bothered to redirect any of these pages there. Now I've moved on from there, and... Finally I am using my real domain, trishagee.com . My blog is now at trishagee.com/blog .  See you there!
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In which I defend the Male species at an all Female event

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Google Campus is an awesome space Today I was at the Girl Geek Meetup conference.  I didn't advertise it much because I've said in the past I don't really agree with women-only events , and actually I felt quite uncomfortable telling you guys I was going to be there, knowing the majority of my readers weren't allowed to attend. It's probably worth explaining why I went, so a) I can give you guys and excuse but b) conference organisers can see what people like me are looking for in a conference. Graduate Developer Community Meet a Mentor Programme The primary reason I went is because the new Meet a Mentor programme I'm involved in does not have a lot of women mentors.  This is simply a numbers game - when you don't have all that many people signed up to be mentors yet, and you have the "normal" proportion of women in that group, you'll be lucky if you get one female mentor turning up at these events.  Since one of the things we want
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Overheard: Agile truths

After attending a number of conferences and events, and performing numerous interviews, I'm starting to hear the same things again and again.  Since Dan North challenged all my assumptions at QCon , I'm reluctant to outright ridicule them, but I will put forward my personal opinion. Note: these are things I have heard from multiple sources, so with any luck I am not breaking the sanctity of the confessional interview. I've never pair programmed, but I've frequently worked with a partner on critical production problems I find this fascinating.  If there's one thing that needs to be fixed as fast, as correctly, as efficiently as possible, it's a production issue.  And when there is one, "everyone" knows that two heads are better than one, even The Business. If this is the case, why is it so hard to sell pair programming as the default state of affairs? Is it because creating new features is seen as just typing, where the bottleneck is access t
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Popular posts from this blog

Dissecting the Disruptor: What's so special about a ring buffer?

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Recently we open sourced the LMAX Disruptor , the key to what makes our exchange so fast.  Why did we open source it?  Well, we've realised that conventional wisdom around high performance programming is... a bit wrong. We've come up with a better, faster way to share data between threads, and it would be selfish not to share it with the world.  Plus it makes us look dead clever. On the site you can download a technical article explaining what the Disruptor is and why it's so clever and fast.  I even get a writing credit on it, which is gratifying when all I really did is insert commas and re-phrase sentences I didn't understand. However I find the whole thing a bit much to digest all at once, so I'm going to explain it in smaller pieces, as suits my  NADD audience. First up - the ring buffer.  Initially I was under the impression the Disruptor was just the ring buffer.  But I've come to realise that while this data structure is at the heart of the patte
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Dissecting the Disruptor: Writing to the ring buffer

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This is the missing piece in the end-to-end view of the Disruptor.  Brace yourselves, it's quite long.  But I decided to keep it in a single blog so you could have the context in one place. The important areas are: not wrapping the ring; informing the consumers; batching for producers; and how multiple producers work. ProducerBarriers The Disruptor code has interfaces and helper classes for the Consumer s, but there's no interface for your producer, the thing that writes to the ring buffer.  That's because nothing else needs to access your producer, only you need to know about it.  However, like the consuming side, a ProducerBarrier is created by the ring buffer and your producer will use this to write to it. Writing to the ring buffer involves a two-phase commit.  First, your producer has to claim the next slot on the buffer.  Then, when the producer has finished writing to the slot, it will call commit on the ProducerBarrier . So let's look at the first bi
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Dissecting the Disruptor: How do I read from the ring buffer?

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The next in the series of understanding the Disruptor pattern developed at LMAX . After the last post we all understand ring buffers and how awesome they are.  Unfortunately for you, I have not said anything about how to actually populate them or read from them when you're using the Disruptor. ConsumerBarriers and Consumers I'm going to approach this slightly backwards, because it's probably easier to understand in the long run.  Assuming that some magic has populated it: how do you read something from the ring buffer? (OK, I'm starting to regret using Paint/ Gimp .  Although it's an excellent excuse to purchase a graphics tablet if I do continue down this road.  Also UML gurus are probably cursing my name right now.) Your Consumer is the thread that wants to get something off the buffer.  It has access to a ConsumerBarrier , which is created by the RingBuffer and interacts with it on behalf of the Consumer .  While the ring buffer obviously needs a se
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