On Tue, Aug 06, 2019 at 08:24:17AM -0400, Vineeth Remanan Pillai wrote: > Peter's rebalance logic actually takes care of most of the runq > imbalance caused > due to cookie tagging. What we have found from our testing is, fairness issue > is > caused mostly due to a Hyperthread going idle and not waking up. Aaron's 3rd > patch works around that. As Julien mentioned, we are working on a per thread > coresched idle thread concept. The problem that we found was, idle thread > causes > accounting issues and wakeup issues as it was not designed to be used in this > context. So if we can have a low priority thread which looks like any other > task > to the scheduler, things becomes easy for the scheduler and we achieve > security > as well. Please share your thoughts on this idea.
What accounting in particular is upset? Is it things like select_idle_sibling() that thinks the thread is idle and tries to place tasks there? It should be possible to change idle_cpu() to not report a forced-idle CPU as idle. (also; it should be possible to optimize select_idle_sibling() for the core-sched case specifically) > The results are encouraging, but we do not yet have the coresched idle > to not spin 100%. We will soon post the patch once it is a bit more > stable for running the tests that we all have done so far. There's play_idle(), which is the entry point for idle injection. In general, I don't particularly like 'fake' idle threads, please be very specific in describing what issues it works around such that we can look at alternatives.
