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Showing posts with the label non-tech

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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What I Did On My Holidays

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And now, a post for my long-neglected, less technical readers. I took a week off in July to try and avoid that Oh My God I Missed Summer Again feeling. Granted, it's easy to get that in the UK even if you're not stuck in an office the entire time. Really this is just an excuse to post some photos on the blog. Monday Hopped on the bike and explored from Kensington to Westminster. Felt distinctly smug when I grabbed my lunch from Victoria amongst all the less fortunate people who had to go back to their offices. Tuesday Decided to dose up on Culture, and went to the National Gallery .  Last time I was there I was eight years old, and I distinctly remember admiring the frames more than the art. The rather marvellous  Artfinder makes up for the fact that you can't take photos inside the gallery - I can share most of the pieces that struck me when I was there. Wednesday Finally got around to embarking on one of the walks in Secret London .  I chose to d...
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Cyclist tribes

Living and working in central London, you quickly learn that the fastest way around town is to cycle. My extensive research into this activity has shown there are a number of different cycling tribes. Of course, I have split them into the two groups that are most appropriate to me: 1) slower than me and 2) faster than me. You can probably tell what sort of a cyclist I am by my attitude to the two groups. 1. Slower than me: Wicker shopping basket. Doesn't matter what the rest of the bike looks like, or the biker, I will always try to get ahead of these.  The extra scary ones are the women in flowing dresses who might be university professors. Boris Bikes .  When there's a tube strike, Avoid At All Costs.  These people probably haven't been on a bike since they were in school, and it shows. Hoody (always a male) on a BMX-style bike with the seat far too low, riding in too low a gear, with baggy jeans that show their... well... everything. Never have lights on th...
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Popular posts from this blog

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: 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: Demystifying Memory Barriers

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My recent slow-down in posting is because I've been trying to write a post explaining memory barriers and their applicability in the Disruptor . The problem is, no matter how much I read and no matter how many times I ask the ever-patient Martin and Mike questions trying to clarify some point, I just don't intuitively grasp the subject. I guess I don't have the deep background knowledge required to fully understand. So, rather than make an idiot of myself trying to explain something I don't really get, I'm going to try and cover, at an abstract / massive-simplification level, what I do understand in the area.  Martin has written a post  going into memory barriers  in some detail, so hopefully I can get away with skimming the subject. Disclaimer: any errors in the explanation are completely my own, and no reflection on the implementation of the Disruptor or on the LMAX guys who actually do know about this stuff. What's the point? My main aim in this s...
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