Revert "tick-sched: recalculate sleep length each time it is requested"

This reverts commit 1c0a4128e47a7673e6e1347ce6dc40427ccc4a16.
ext4: remove unused variable

Signed-off-by: poondog <markj338@gmail.com>
slub: fix uninitialized variable

Signed-off-by: poondog <markj338@gmail.com>