1. Be consistent in the style of "act_delta" manipulations between the
inactive and active queue scans.
2. Explicitly compare to zero.
3. The deactivation of a page is based is based on its recent history
and not just the current call to vm_pageout_scan(). The variable
"act_delta" represents the current state of the page, and not its
history. Avoid possible confusion by not (ab)using "act_delta" for
the making the deactivation decision.
Submitted by: kib [1]
Reviewed by: kib [2,3]
86fa24710e