Very fast, header only or compiled, C++ logging library

 Features: Very fast - performance is the primary goal; Headers only; No
 dependencies - just copy and use; call style using the excellent cppformat
 library; ostream call style is supported too; Optional extremely fast
 asynchronous mode - using lockfree queues and other tricks to reach millions
 of calls/sec; Custom formatting; Multi/Single threaded loggers; Easily
 extendable with custom log targets (just implement a single function in the
 sink interface). Severity based filtering - threshold levels can be modified
 in runtime as well as in compile time.
 .
 Various log targets:
 Rotating log files, Daily log files, Console logging, Linux syslog.