ios - Debug navigator memory in Xcode grows -

i have developed application iphone, , check memory leak.

i switch 2 viewcontrollers (two screens), vc1 , vc2 follow:

1. click button in vc1 start vc2, using [self presentviewcontroller:vc2 animated:yes completion:nil];

2. click button in vc2 close vc2 , go vc1, using [self dismissviewcontrolleranimated:yes completion:nil];

i repeats step 1 , 2 ten times.

in xcode, debug navigate memory, memory grows each time

screen @ vc1, memory: 6mb

screen @ vc2, memory: 6.6mb

screen @ vc1, memory: 6.3mb

screen @ vc2, memory: 6.8mb

screen @ vc1, memory: 6.5mb

screen @ vc2, memory: 7mb

screen @ vc1, memory: 6.6mb

screen @ vc2, memory: 7mb

screen @ vc1, memory: 6.6mb

screen @ vc2, memory: 7.2mb

...

screen @ vc1, memory: 7mb

vc1 starts memory 6mb, @ end, uses 7mb, after 10 time switching of vc1 , vc2.

i verify code , run xcode instrument find memory leak, instrument shows no leak.

what cause memory grow 6mb 7mb?

my application has memory leak?

or normal behaviour of ios?