On Sun, 2007-08-26 at 01:09 -0700, Andrew Morton wrote: > On Sun, 26 Aug 2007 10:47:24 +1000 Rusty Russell <[EMAIL PROTECTED]> wrote: > > Userspace is not monolithic. If you refuse to take a CPU offline > > because a task is affine, then any user can prevent a CPU from going > > offline. > > That's a kernel bug.
You mean "would be if it were implemented"? Although consider the equivalent forkbomb or thrashing userspace problems, where we just say "use quotas". Just to clarify: that is not how we work, we migrate tasks off a dying CPU, breaking affinity and printing a warning if necessary. It was simple and has not proven problematic in practice. (Userspace cpu affinity has been a question of optimality not correctness) > > You could, perhaps, introduce a "gentle" offline which fails if process > > affinity can no longer be met. > > Suitably privileged userspace should be able to > > 1) prevent tasks from binding to CPU N then > 2) migrate all tasks which can use CPU N over to other CPU(s) then > 3) offline CPU N. Indeed, (1) is missing. I would hesitate to introduce more infrastructure in an under-worn and over-buggy part of the kernel though. Rusty. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/