On Wed, May 01, 2024 at 11:31:02AM -0400, Michael S. Tsirkin wrote: > On Wed, May 01, 2024 at 12:51:51PM +0200, Peter Zijlstra wrote: > > I'm still wondering why exactly it is imperative for t2 to preempt t1. > > Is there some unexpressed serialization / spin-waiting ? > > > I am not sure but I think the point is that t2 is a kworker. It is > much cheaper to run it right now when we are already in the kernel > than return to userspace, let it run for a bit then interrupt it > and then run t2. > Right, Tobias? So that is fundamentally a consequence of using a kworker. So I tried to have a quick peek at vhost to figure out why you're using kworkers... but no luck :/ Also, when I look at drivers/vhost/ it seems to implement it's own worker and not use normal workqueues or even kthread_worker. Did we really need yet another copy of all that? Anyway, I tried to have a quick look at the code, but I can't seem to get a handle on what and why it's doing things.
