2008/7/25 Peter Zijlstra <email@example.com>:
I've considered using get_online_cpus() for a moment but dropped this
idea exactly because I thought it would harm us latency-wise.
cpu_down() and cpu_up() may take quite a long time to complete and
load_balance() && load_balance_idle() would need to wait all this
time. And they both are kind of generic (primary) scheduler
but yea, my scheme relies on the fact that load_balance() &&
load_balance_idle() are atomic one way or another wrt. cpu_clear() +
synchronize_sched() in cpu_down().
[ speculating here ] I'd rather add an additional mechanism which
would be light-weight for load_balance() and add
synch_this_mechanism() (alike to synchonise_sched()) in cpu_down() as
perhaps we don't care that much on how fast the later one is.