On Wed, 16 Jan 2013 16:49:21 -0500 Steven Rostedt <[email protected]> wrote:
> On Wed, 2013-01-16 at 13:18 -0800, Andrew Morton wrote: > > On Wed, 16 Jan 2013 17:16:37 +0100 > > > I still don't understand NOHZ's role in this whole thing :( > > It's not for idle NOHZ, but "process" NOHZ. > > That is if we have only one task running on a CPU, we don't want a tick > interrupt to bother it. This is because there's lots of users out there > that want an uninterrupted task. A task that doesn't ever get bothered > by the kernel. If it's in userspace, it stays in userspace (no > interrupts), until it calls into the kernel itself (syscall). Even when > its in the kernel, we still don't need the tick interrupt if its the > only task. oh, is that what TIF_NOHZ does ;) > But the scheduler isn't the only thing that uses this tick. To remove > the tick, we need to satisfy all the other users (printk, delayed work, > u/s-times). > > To still keep up the stats of user and kernel times for the task, we > need to record when the task switches from user to kernel and back > again. Hence the context tracking code. > > Makes more sense? yup thanks. -- 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/
