Accoding to Ian Carr, the fillCallerData method is called even for disabled log statements.

private void log(String callerFQCN, Level level, String msg, Throwable t)

{ // millis and thread are filled by the constructor LogRecord record = new LogRecord(level, msg); record.setLoggerName(getName()); record.setThrown(t); fillCallerData(callerFQCN, record); <-- bad logger.log(record); }

For more information see http://www.slf4j.org/pipermail/user/2008-February/000486.html