Venkatesh's VM idle page zeroing code has been committed. I used a
squashed merge and rolled in some additional fixes for problems that
came up during testing, so our main repo probably won't sync with
Venkatesh's repo now.
It currently defaults to disabled. We will change the default to
enabled once we do a little more testing. 'sysctl vm | fgrep zero'
gets you all the sysctls.
It doesn't make a huge difference when testing a parallel buildworld,
*maybe* saving 20 seconds on a 1200 second build. I expect that it
will make more of a difference for burst or serialized operations such
as shell script execution where cpus have enough idle time to
pre-zero more pages.
The page zeroing rate has been bumped up to levels more condusive to
expected workloads, around 20,000 pages per second max.
-Matt
