Question

i use NSLog many times,and i know that it has a delay time .
my app has a delay time ,and i wonder if many logs can create that.

for example, if i have this code :

samplerTimer = [NSTimer scheduledTimerWithTimeInterval: 0.001f target: self selector: @selector(CheckData) userInfo: nil repeats: YES];
NSLog(@"%f",tmp);

the timer is calling a function each 1ms,and it works great, but my concern is that the log takes more time so the timer routine kind of change.
i use hardware,so mseconds are important.

i am trying to understand,what exactly happen during nslog? the system is sleeping? other things are done in parallel ?
how much time exactly does it take ?

Answer 1

NSLog() writes to the standard output or error using printf. It will also cause a flush, meaning that the program blocks until the output has been sent to the OS. This is slow.

Removing the NSLog() statements will speed things up a lot. The easiest way to turn all logging off, is adding:

#define NSLog(...) 0

in your prefix header (the .pch file), below the framework includes. Or you could add this line in the files you want to silence. If effectively replaces all NSLog() statements with 0, which does nothing.