I've also profiled this code, and found some not-too-suprising results (also attached):
- When the logger is enabled, the bulk of this program's time is spent in boost:logging::enabled_logger::~enabled_logger, which is calling write_msg with the result of std::ostringstream::str.
- When the logger is disabled, much of the time is spent in ~enabled_logger as well as the is_enabled check
Overall, the performance of the Boost.Log library when output is enabled is almost an order of magnitude slower than just writing the same data to a standard iostream. I believe the overhead of the enabled_logger design (object creation, heap allocation of an ostringstream every time a message is logged) might bear some re-examination. Is the enabled_logger object
Yes, heap allocation does consume a lot of time.
really necessary? Can the ostringstream be created on the caller's stack instead of the heap (e.g. by re-writing the BOOST_LOG macro) or perhaps re-used?
I believe that the syntax of the logging macros (e.g. BOOST_LOG (x) << ...), while clever, contributes to the relatively poor performance of the library when compared to bare iostreams. I would suggest that by enclosing the entire logging statement in the macro invocation (e.g. BOOST_LOG(x, ...) ), a more optimal, feature-rich implementation is be possible. It becomes exceedingly simple to implement compile-time removal of logging calls with the "enclosed" macro-based interface, obviating the need for the is_compile_time complexities in the current code. Additionally, messages might be logged with __FILE__ and __LINE__ information automatically (if so
Yes, I'll allow for __FILE__, __LINE__.
desired). I'm sure there are other benefits (and weaknesses) that I'm overlooking as well.
Thanks Caleb. I will definitely use this as a start, when implementing the new version of the logging lib. A lot of optimizations can be done, especially on the macro area. Best, John -- John Torjo, Contributing editor, C/C++ Users Journal -- "Win32 GUI Generics" -- generics & GUI do mix, after all -- http://www.torjo.com/win32gui/surfaces.html - Sky's the limit! -- http://www.torjo.com/cb/ - Click, Build, Run!