Chasing Performance

1 May 2013

Tags

  • Fairy Tale Twist
  • Performance

It’s always interesting putting a code-base you’re familiar with to a new platform, typically involving a new compiler (new and different errors, warnings and libraries) and exercises the code in different places. In this instance, running under the browser we’re hitting memory hard. Interestingly _strlen is in the top 30 in a profile trace, and drilling into call stacks our string handling and parsing feature in inner loops.

Fixes included:

  • switching events from using std::string to char , all of the defines for types of events are static and const char, which were then promoted to temporary std::strings. Removing this dropped events from the callstack.
  • switching our xml accessors from returning std::string to char, natively libxml returns xmlChar which can be aliased to char*, avoiding another std::string promotion.
  • switching from parse<int> and parse<float> to, old school, atoi and atof, again avoiding temporary promotion to std::string And there is more scope for switching away from strings to char* and from strings to int (there are a few places where numbers are passed as strings). After two days of optimizing load times when from 30-60secs to 11seconds.
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