On Mon, Oct 22, 2018 at 07:59:31AM -0700, Steve Sistare wrote: > When a CPU has no more CFS tasks to run, and idle_balance() fails to > find a task, then attempt to steal a task from an overloaded CPU in the > same LLC. Maintain and use a bitmap of overloaded CPUs to efficiently > identify candidates. To minimize search time, steal the first migratable > task that is found when the bitmap is traversed. For fairness, search > for migratable tasks on an overloaded CPU in order of next to run. > > This simple stealing yields a higher CPU utilization than idle_balance() > alone, because the search is cheap, so it may be called every time the CPU > is about to go idle. idle_balance() does more work because it searches > widely for the busiest queue, so to limit its CPU consumption, it declines > to search if the system is too busy. Simple stealing does not offload the > globally busiest queue, but it is much better than running nothing at all.
Why I don't dislike the idea; I feel it is unfortunate to have two different mechanisms to do effectively the same thing. Can't we improve idle_balance() instead of building this parallel functionality?
