Lessons Learned from Multithreading
Posted by Jason Z, 10 September 2010 · 323 views
My posts haven't been very frequent lately due to being extremely busy working on a book project. There are two other authors working with me, and I think the project is really starting to shape up. Even with all of the writing, I have still been working on Hieroglyph 3 here and there when I get a chance.
With the addition of text rendering (as described last time) into the engine, it produced somewhat of a collision with my new multithreaded rendering features. The multithreading system more or less takes a render view and processes it on one of deferred contexts, each of which is running on its own thread. Currently I hard code the number of threads, but eventually I will just detect how many cores are available in the host system and automatically adjust. Once all of the deferred contexts have produced command lists, they are all executed in the proper order on the immediate context.
The problem with requiring all render work to exist within render views is that you can't just hack things in to get it displaying. The actual root of the problem is that the immediate context doesn't retain its pipeline state after processing a bunch of command lists... so trying to put text up when there is no render target, blend state, depthstencil state, etc... doesn't work so good.
So to put some text up onto the screen for debugging messages or whatever, I actually need to put all of the state setting and drawing calls into a render view and draw them via the deferred contexts. This is actually the correct thing to do since it fits into the MT design system. However, I want to make it as easy as possible for applications to use text rendering, so I will be making a Text Render View that will be available as part of the application class to add messages to and render. It should work out, I just need to find the time to put it all together and test it out...
The moral of this little surprise is this: when you design a system to make a particular requirement for your applications to follow, don't be surprised when you actually need to follow your requirements to make something work!
By the way, if anyone has had a chance to look at the Hieroglyph 3 engine, I would love to hear any feedback that you might have or suggestions for improvement. The documentation is still on hold due to the book project, but it should start to slowly emerge as time opens up...