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. 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? -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
