Posts

Showing posts from March, 2013

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!
Post a Comment
Read more

It Depends

Don't you hate it when you ask a perfectly good question, and someone comes back with the answer "it depends"? It's so frustrating to think that in a world of ones and zeros, people can't give absolute answers and you can't rely on "best practice". It's an answer I've given so many times, especially when someone asks about performance.  Well, I've had my comeuppance.  The entire exercise of designing the new Java driver for MongoDB has been nothing but a series of questions where the answer is "it depends": Which Java version are our users, um, using? Do people want an asynchronous driver? How will they want to work with async? Will they want to use async and synchronous method calls from the same application? Do people typically use the Java driver directly, or do they use something that wraps it, like Morphia or Spring Data ? What's most important for users in terms of performance?  Throughput? Latency? Consis
2 comments
Read more

Upcoming Events

Following on from a busy and fun QCon, I can now let you in on the next set of events I'll be at: 21st March - LJC: What do you mean, backwards compatibility ? 27th March - DevoxxUK: What do you mean, backwards compatibility ? 27th March (evening) - Hope to attend the London CTOs meetup . 9th April - MongoDB London : Schema Design 10th April - East Anglia MUG: Trisha Gee Unconference 15-17th May - GeeCON , Krakow 18-19th June - GOTO Amsterdam (I think, although I'm not on their site!) Note that I'm actually going to be in the UK for all of March and April (at the moment), which will be a nice change. I'm hoping to be able to speak about the same types of things for the rest of the year, it has been exhausting presenting on new topics for every event over the last 6 months.  I'll happily take feedback on what people are most interested in hearing about.
Post a Comment
Read more

The Coalescing Ring Buffer

For anyone who is interested in what LMAX is up to, and is still following my blog, have a look at this post about the latest tool they've open sourced: the Coalescing Ring Buffer .
3 comments
Read more

QCon Day One

Image
I like QCon London, I really do.  Not only is it on home turf, but, as I've said before , it doesn't just focus on technology, or a set of technologies. Full disclosure: I've been involved in planning QCon this year.  So this time I know all the thinking, hard work, planning and last-minute changes that go into a conference like this.  And it's a joy to be able to sit in the audience and see the conference that you've helped build. There are things I took out of today that I want to get down on "paper" now, because I think the next few days will have different themes. Let's Not Forget About Computer Science I'm so pleased to see this in a conference!  After documenting and talking about the Disruptor so much last year, I felt it was important for us to go back to our roots a bit, and have some Mechanical Sympathy .  Some of the sessions today brought us back to the school room and had us thinking about the tools we're using. In my
Post a Comment
Read more

GDL Presents Women Techmakers with Trisha Gee

Image
I was flattered a couple of weeks ago to be interviewed by Google as part of their women techmaker's series, as it moves over to Europe. In this video I talk about going to Mars, education, planning your career, being a developer, and the impact of technology on our lives. So, not much...  
Post a Comment
Read more

Popular posts from this blog

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

Image
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
Read more

Dissecting the Disruptor: Writing to the ring buffer

Image
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
Read more

Dissecting the Disruptor: How do I read from the ring buffer?

Image
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
Read more