On Thu, Dec 14, 2017 at 12:50:13PM -0600, Christopher Lameter wrote: > Ultimately I wish fast increments like done by this_cpu_inc() could be > implemented in an efficient way on non x86 platforms that do not have > cheap instructions like that.
So the problem isn't migration; for that we could wrap the operation in preempt_disable() which is not more expensive than rseq would be. And a lot more deterministic. The problem instead is interrupts, which can result in nested load-store operations, and that comes apart. This then means having to disable interrupts over these things and _that_ is expensive.
