Back in 2004, I wrote a series of articles called “Practical Testing” where I took a piece of complicated multi-threaded code and wrote tests for it. I then rebuild the code from scratch in a test driven development style to show how writing your tests before your code changes how you design your code. Since the original articles there have been several bug fixes and redesigns all of which have been supported by the original unit tests and many of which have led to the development of more tests.
Previously on “Practical Testing”… I’ve been looking at the performance of the timer system that I developed and have built a more specialised and higher performance timer system which is more suitable for some high performance reliable UDP work that I’m doing. Whilst developing the new timer wheel I began to consider the thread contention issues that the timer system faced and came up with a notation for talking about contention (see here).
Previously on “Practical Testing”… I’m writing a timer wheel which matches the interface used by my timer queue. This new implementation is designed for a particular usage scenario with the intention of trading space for speed and improving performance of some reliable UDP code. The last entry completed the development of the timer wheel. This time we fix a couple of the bugs that I’ve discovered since I started to integrate the code with the system that it was developed for.
Previously on “Practical Testing”… I’m writing a timer wheel which matches the interface used by my timer queue. This new implementation is designed for a particular usage scenario with the intention of trading space for speed and improving performance of some reliable UDP code.
Over the last four entries I’ve implemented various parts of the timer wheel and adjusted the test code so that I could reuse the tests that I already had for the other implementations with my timer wheel.
Previously on “Practical Testing”… To deal with some specific usage scenarios of a piece of general purpose code I’m in the process of implementing a timer wheel that matches the interface to the timer queue that I previously developed in this series of articles. Last time I left myself with a failing test. The problem is that setting a new timer on the timer wheel sets a timer that’s relative to the time that timer wheel thinks is ’now’ and the timer wheel’s view of the current time could be slightly behind reality; see the previous entry for a diagram that explains the problem.
Previously on “Practical Testing”… To deal with some specific usage scenarios of a piece of general purpose code I’m in the process of implementing a timer wheel that matches the interface to the timer queue that I previously developed in this series of articles. The timer wheel trades space for speed and so far the development has gone well as I’ve been able to use the tests that I had already developed for the previous implementations to guide the new development.
I’m in the process of implementing a timer wheel that matches the interface to the timer queue that I previously developed in this series of articles. The idea being that for certain specific usage scenarios the timer wheel will perform better than the timer queues. Last time I refactored the tests that I was using for the timer queues to remove duplication and I now have a set of failing tests for the new timer wheel.
The most recent articles in the “Practical Testing” series have been discussing the performance of the timer queue that we have built. Once I had got some new, optional, performance tests in place to measure what we were trying to improve I eventually came up with a new approach and began to implement a timer wheel that conforms to the interface used by the other implementations of my timer queue. Whilst doing this it became obvious that there was duplication in my test code and so the tests have been refactored to remove the duplication of the test code between CCallbackTimerQueue and CCallbackTimerQueueEx and, in addition, to create a full suite of tests for the new CCallbackTimerWheel class.
The most recent articles in the “Practical Testing” series have been discussing the performance of the timer queue that we have built. As I hinted when I first brought up the performance issues, the particular use case that I have which is causing problems might well be more efficiently dealt with using a different (more specialised and less general purpose) design.
The timer queue has adequate performance for general purpose use and can handle timers set within a range of 0ms to 49.
The previous article in the “Practical Testing” series set things up so that we can measure the performance of the code under test with the intention of trying to improve performance for a specific set of use case scenarios. This time around I’ll make a few changes which I hope will improve the performance and measure the effects of the changes with the performance tests that I added last time.
