Log4cxx Performance

One important question with a logging library is: is it fast enough? While Log4cxx may not be the fastest logging implementation, it is more than fast enough for the vast majority of cases.

In performance testing done on a developer's system(utilising an Intel i5-8400 processor and a virtual machine), it is possible for Log4cxx to handle over 2,000,000 messages/second in a single-threaded application. Since Log4cxx is designed to be multithread-safe, logging from multiple threads makes this throughput much lower. Delays in writing messages to disk can also greatly decrease performance, depending on how much data is being logged.

If the logging of a particular level is disabled, performance can also be a lot better. While Log4cxx can handle 2,000,000 log messages/second, when the log statement is disabled(not logged), this can go to over 20,000,000 messages/second, thus not unduly slowing down an application when logging is disabled.

For the best performance, the LOG4CXX_[level]_FMT series of macros should be utilized, as they use the {fmt} library(note that you must include the headers from {fmt} manually). Using {fmt} over operator<< for log messages is both cleaner from a code standpoint, and is also significantly faster(approximately 2x as fast).

These two pieces of logging code are logically equivalent(printing out the same values), however the one utilizing fmt is close to 2x as fast.

for( int x = 0; x < howmany; x++ ){
         LOG4CXX_INFO( logger, "Hello logger: msg number " << x);
}

for( int x = 0; x < howmany; x++ ){
    LOG4CXX_INFO_FMT( logger, "Hello logger: msg number {}", x);
}

If you wish to benchmark Log4cxx on your own system, have a look at the tools under the src/test/cpp/throughput and src/test/cpp/benchmark directories. The throughput tests may be built by specifying BUILD_THROUGHPUT with CMake when building Log4cxx. The benckmark tests require the {google benchmark} library and may be built by specifying BUILD_BENCHMARK_CHECKS with CMake when building Log4cxx.

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Log4cxx Performance