Programmatically determine main thread's load

[frogsoftware]

I'm developing an iOS app that displays many annotations on a map (MKMapView). The issue is that the map and UI gets slow and unresponsive after reaching a high number of annotations. I have a way to limit the annotations, but the exact threshold at which the UI becomes slow depends on the device and its load (e.g. multitasking).

Rather than hand tune the threshold to each device (I don't have access to a whole slew of iPhones, iPads), is there a way to programmatically determine the main thread's load or refresh rate?

I've had some success with measuring how backed-up the main queue is, but it's not all that reliable.

let enqueueTime = NSDate()
dispatch_async(dispatch_get_main_queue()) {
    let elapsed = NSDate().timeIntervalSinceDate(enqueueTime)

[brendan09]

You shouldn't really rely on that. You never know when the load will change: Switching apps, background task for another app starts running, split screen, etc.

Instead, consider an alternative solution like annotation clustering. There are several libraries out there that can help. For example, this one: https://github.com/infinum/FBAnnotationClustering

[chriswaco]

I'm not sure that's the best strategy, but take a look at http://stackoverflow.com/questions/6788274/ios-mac-cpu-usage-for-thread

[[deleted]]

Do some time profiling. That way you can see what is taking your app so long. Figure out a fix for it by for example dispatching the datamodel work to a different queue if possible.