iOS Why is faster when run with instrument?

[mikezang]

I made Tabbar Controller and build one of tab in SplitView Controller, then I read a 5000 lines text file and filter some lines, then put those lines into table in master view of split, it is very slow when run both in debug or release mode.

Then I found a very strange thing, when I run it in instrument mode, the speed is very fast that is over what I can think.

I want to know why and which speed is true when I run it in my device?

 

[mikezang]

I got the reason, because I run it with GuardMalloc, this is very slow!
Then it disabled GuardMalloc when run with Instrument.