Why is my macbook pro non-retina slow to sleep (15-20 s) despite no sleepimage? So, the situation:


non-retina macbook pro mavericks OS X or newer
have to wait 15+ seconds for macbook to sleep
already tried setting hibernatemode=0 (no sleepimage)
see the following text after typing pmset -g log in the terminal:


TimedOut InternalPreventSleep "com.apple.powermanagement.darkwakelinger" 00:00:15
The XLab website says that this 15 sec delay is likely something Apple has added for Mac's that support PowerNap. DarkWake is assumed to be an internal name for PowerNap, and is referenced on a Patent. 

For more, please visit the article on Xlab:

http://www.thexlab.com/faqs/mavericks_post_install.html#Delay_before_sleep