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Showing posts from July, 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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On The Evil Of Stereotypes

I attended (one way or another) two events last week that got me thinking The first was  Girl Developers will Save the World  - a session that had me a little confused as to whether that referred to me, or  actual  girls, i.e. those that are not yet legally classed as adults.  The second was the  Remarkable Women Twitter  party the following day. Firstly, a caveat/disclaimer (as usual) - both events were useful, thought-provoking and overall worthwhile.  But the alarming thing to me was the number of times I heard "boys are…" or "women think…" or "girls prefer…".  And I know we often make generalisations to stress a point, but I'm becoming extremely wary of statements that group people together along some arbitrary boundaries.   "Google+ failed because it's design by men for men" - no, it's because it's not designed for anyone.  Its only purpose was to compete with Facebook. "Women are better at communicating an...
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OSCON Day One

So, my first day at my very first OSCON .  I have to say that when Ben and Martijn told me I had to do OSCON, that it was one of the conferences to go to, I was sceptical - not because I thought it would be rubbish, but because I have enjoyed all the conferences I've been to for different reasons. But I'm really impressed so far. The program is packed with great topics and speakers, and so many things I want to see that clash with each other.  It's frustrating, and all the sessions get in the way of all that networking stuff! The people are so friendly.  They smile at you randomly in the corridor.  They talk to you for no reason.  As a Londoner it comes as a bit of a shock to the system.  And it's nice!  Great conversations with different people. The venue  is set up for these encounters with plenty of places to sit with the laptop or mingle or meet and sit with people at lunchtime. The exhibition area is not a total waste of time...
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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 hea...
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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...
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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 n...
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