Measure iOS app startup time, in seconds, from the time user tapped an icon on the home screen (using time, when app process was created). Swift 4.

MeasureAppStartupTime.swift

// Returns number of seconds passed between time when process was created and function was called
func measureAppStartUpTime() -> Double {
    var kinfo = kinfo_proc()
    var size = MemoryLayout<kinfo_proc>.stride
    var mib : [Int32] = [CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()]
    sysctl(&mib, u_int(mib.count), &kinfo, &size, nil, 0)
    let start_time = kinfo.kp_proc.p_starttime
    var time : timeval = timeval(tv_sec: 0, tv_usec: 0)
    gettimeofday(&time, nil)
    let currentTimeMilliseconds = Double(Int64(time.tv_sec) * 1000) + Double(time.tv_usec) / 1000.0
    let processTimeMilliseconds = Double(Int64(start_time.tv_sec) * 1000) + Double(start_time.tv_usec) / 1000.0
    return (currentTimeMilliseconds - processTimeMilliseconds) / 1000.0
}

Where do you call this function? In root view controller or somewhere else?

It doesn't matter where it is called from. Call it from where you need it. The code goes off and checks when the unix process was created (not when your view was created).

You should call this function as early as possible. If your app has main.swift, this would be a great place. If not, you can try calling it in your AppDelegate init (it’s also helpful to call it in applicationDidFinishLaunching to find out how long does your application start after process has been spawned).

There is a problem with processTimeMilliseconds . Sometimes I get a wrong result, it is much earlier than the real launch time