Contributors to this thread:

The Ktistec executable is now ~24.7% smaller and build times are 28% faster.

I've been blogging about optimizations here, here, and here. This is the summary of the final outcome, with links to commits for the curious. I have one more post planned with a summary of my thoughts.

Here's my approach. Use nm to dump the symbols in a release build executable and then look for things that seem redundant. The first change and associated post below is a great example of what I mean—my original implementation led to the specialization of the #== method for every pairwise combination of model classes even though the result of the comparison was just false.

This might seem like a strange approach if you come from a compiled language where you mostly write all of the code yourself or invoke generics explicitly, but Crystal takes your code and does that for you. And it's not always obvious up front (to me, at least) what the final cost will be.

I've include counts of the lines added/removed because the point of this whole post is to say if you measure first and then optimize, a small change can have a big impact.

Here are the changes:

  • Specialize model #==. (+7 -5)
    I talked about this here but didn't have the commit to link to. This change results in a large reduction in executable size on regular builds (~4.0%) and a small difference on release builds (~0.2%).
  • Remove conversion to Hash. (+2 -2)
    This commit eliminates specialization of methods like __for_internal_use_only that get passed both named tuples and hashes by going all in with named tuples. It also eliminates instantiations of the Hash generic type itself for these cases. Reduces executable size by ~2.2%.
  • Eliminate duplicate code in the executable. (+3 -3)
    This small change reduces the size of the executable by a further ~0.4% by eliminating redundant definitions of __for_internal_use_only entirely.
  • Make InstanceMethods instance methods. (+1 -5)
    This was a goofy design I picked up somewhere. It's unnecessary. Changing this saves ~0.2% on release build executable size.
  • Move the code for digging through JSON-LD. (+246 -281)
    It looks like a lot of lines of code changed here, but the large numbers are the result of moving code line-by-line from an included module to a utility class. Invoking these as methods on the utility class rather than as instance methods on each including class reduces the executable size by ~0.5%.
  • Use map from base ActivityPub model classes. (+10 -2)
    map is a class method defined on each ActivityPub base model class. Each definition maps JSON-LD to a hash that is used to instantiate the class. Class methods defined on a base class are available on subclasses, as well. Calling the method on the subclass results in a copy of the method. This change reduces the executable size by ~5.8%.
  • Move map into helper. (+104 -88)
    The map method does not depend on class/instance state. This change ensures that the mapping code is not duplicated even if a subclass's map method is accidentally again called. It looks like a lot of changes but this commit is mostly reorganization. It reduces executable size by ~0.4%.
  • Replace classes with aliases. (+62 -148)
    Implementing ActivityPub's vocabulary with discrete model classes is expensive because every model class comes with machinery for type-specific CRUD operations. Enumerate aliases on each base model class (e.g. a "Service" is an "Actor"). This change reduces executable size by ~16.9%.

I'm off to optimize some queries now...

#ktistec #crystallang

reflecting on this, __for_internal_use_only is a really poor name...