The IInetLogInformation::GetTimeForProcessing method retrieves the number of milliseconds it took for the operation to complete.
virtual DWORD STDMETHODCALLTYPE GetTimeForProcessing( VOID );
Logging modules should query for this method if a server instance has set the MD_EXTLOG_TIME_TAKEN flag of the MD_LOGEXT_FIELD_MASK metabase identifier.
LogExtFileTimeTaken, MD_LOGEXT_FIELD_MASK