On 10 July 2014 13:18, Peter Zijlstra [off-list ref] wrote:

On Mon, Jun 30, 2014 at 06:05:39PM +0200, Vincent Guittot wrote:

quoted

+             /*
+              * If the CPUs share their cache and the src_cpu's capacity is
+              * reduced because of other sched_class or IRQs, we trig an
+              * active balance to move the task
+              */
+             if ((sd->flags & SD_SHARE_PKG_RESOURCES)
+              && ((capacity_orig_of(src_cpu) * 100) > (capacity_of(src_cpu) *
+                                                     sd->imbalance_pct)))
                      return 1;

Why is this tied to shared caches?

It's just to limit the change of the policy to a level that can have
benefit without performance regression. I'm not sure that we can do
that at any level without risk