On Sat, Sep 09, 2017 at 09:42:12PM -0700, Andy Lutomirski wrote: > PeterZ and Ingo, would you be okay with adding a define so arches can > opt out of the task_struct::active_mm field entirely? That is, with > the option set, task_struct wouldn't have an active_mm field, the core > wouldn't call mmgrab and mmdrop, and the arch would be responsible for > that bookkeeping instead? x86, and presumably all arches without > cross-core invalidation, would probably prefer to just shoot down the > old mm entirely in __mmput() rather than trying to figure out when do > finish freeing old mms. After all, exit_mmap() is going to send an > IPI regardless, so I see no reason to have the scheduler core pin an > old dead mm just because some random kernel thread's active_mm field > points to it.
I'm only quickly skimming this thread, but I don't see anything too worrysome being proposed. If you're in LA next week we can talk about it in more detail if you want.
