django: guidelines for speeding up template rendering performance

Question

How would I go about speeding up Django template rendering? My template takes about 1-2 seconds or so to render, after the view function fully computes whatever it needs to.

I've already attempted to perform all database access in the view, such that the template only hits RAM and not the DB engine.

I do have a lot of includes - could there be an issue there?

Answer 1

I just spent a good deal of time optimizing my django templating code. Below are optimization guidelines that worked for me, but depending on your setup, you may not get as significant of a speedup.

• Feed the Templating Engine unicode, not str: Django coerces all variables to unicode. This doesn't take too long to do, but if a str variable is being used in many places in your templates, it can turn into a noticeable delay. This is very easy to fix, whenever you're sending text data to a Django renderer, make sure it's unicode.
• Mark Variables as safe: Django's automatic security measures are really nice, but they do come with a small performance hit. If you're using many variables in your template, and you know that it's safe, then be sure to mark it as such.
• Cache Compiled Templates: When you call render_template_from_string, django pulls the template, compiles it, and then renders it. Django makes it easy to cache the first two parts of this process and store them in memory. All you need to do is make one small change in your settings.py file to add cached.Loader to your TEMPLATE_LOADERS. More is explained in the Django documentation.
• Fix or Don't Use endless pagination: I found that the endless pagination plugin slowed things down extremely. That's because it has to load a new template for every single page number. I went in and hacked at it until I got it doing what I wanted, but before you do that, try removing it and see what type of performance improvement you get.
• Don't Use Fancy Templating Features: Inheritance, nested blocks, for loops, and includes are great, but they come with a performance cost. Be very careful when using them and try not to do multiple levels of inheritance. For loops may be better handled with client side rendering.
• Client Side Rendering: An easy trick to speed up server side rendering is to just do it on the client. One strategy is to embed a json structure in the django template, and then have javascript build the HTML. This obviously defeats the purpose of django server side rendering, but it will result in a speedup. This is especially useful if you have to render content below the fold (i.e., the user does not need to see it immediately when the page loads).

Doing the above cut my rendering time of a complex page on a GAE instance from about 1.0S to 250ms, but again, your mileage may vary.