Home » Author Archives: Peter Lawrey (page 4)

Author Archives: Peter Lawrey

Mixing memory unit messages

One of my pet hates is developers messing up units of memory.  In general, the difference doesn’t matter much, or you can work out what they meant to say, but it does annoy me when developers who should know better appear to be confused about what they are trying to say. From Wikipedia’s Byte page, here is a cheat sheet of ...

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Java Lambdas and Low Latency

Overview The main question around the use of Lambdas in Java and Low Latency is; Does they produce garbage and is there anything you can do about it? Background I am working on a library which supports different wire protocols. The idea being that you can describe the data you want to write/read and the wire protocol determines if it ...

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How and Why is Unsafe used in Java?

Overview sun.misc.Unsafe has been in Java from at least as far back as Java 1.4 (2004). In Java 9, Unsafe will be hidden along with many other, for-internal-use classes. to improve the maintainability of the JVM. While it is still unclear exactly what will replace Unsafe, and I suspect it will be more than one thing which replaces it, it raises the ...

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On heap vs off heap memory usage

Overview I was recently asked about the benefits and wisdom of using off heap memory in Java. The answers may be of interest to others facing the same choices. Off heap memory is nothing special. The thread stacks, application code, NIO buffers are all off heap.  In fact in C and C++, you only have unmanaged memory as it does not have ...

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Chronicle Map and Yahoo Cloud Service Benchmark

Overview Yahoo Cloud Service Benchmark is a reasonably widely used benchmarking tool for testing key value stores for a significant number of key e.g 100 million, and a modest number of clients i.e. served from one machine. In this article I look at how a test of 100 million * 1 KB key/values performed using Chronicle Map on a single ...

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Kafka Benchmark on Chronicle Queue

java-interview-questions-answers

Overview I was recently asked to compare the performance of Kafka with Chronicle Queue.  No two products are exactly alike, and performing a fair comparison is not easy.  We can try to run similar tests and see what results we get. This test is based on Apache Kafka Performance Results.         What was the test used? One ...

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Men in Tech

Background Between my partner and I, we have six daughters, and as they have grown I have thought more interested in their long term future, the role of women in society, the way technology will change our lives and in particular the role of women in technology. On the last topic, all the articles I have read have been written ...

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lambdas and side effects

Overview Java 8 has added features such as lambdas and type inference. This makes the language less verbose and cleaner, however it comes with more side effects as you don’t have to be as explicit in what you are doing. The return type of a lambda matters Java 8 infers the type of a closure. One way it does this ...

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An Inconvenient Latency

Overview Vendors typically publish numbers they are happy with, and avoid telling you about a product’s weaknesses.  However, behind the numbers is a dirty secret if you know where to look. Why don’t we use GPUs for everything? Finding problems which naturally scale to thousands of data points/tasks is easy for some problems, and very hard for others.   GPUs ...

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