On Mon, Mar 14, 2011 at 04:46:52PM -0700, Andrew Morton wrote: > On Mon, 14 Mar 2011 16:05:24 +0200 > Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote: > > > +Overview > > +-------- > > + > > +Every task_struct has timer_slack_ns value. This value uses to round up > > +poll() and select() timeout values. This feature can be useful in > > +mobile environment where combined wakeups are desired. > > + > > +Originally, prctl() was the only way to change timer slack value of > > +a process. So you was not able change timer slack value of another > > +process. > > + > > +cgroup subsys "timer_slack" implements timer slack controller. It > > +provides a way to set minimal timer slack value for a group of tasks. > > +If a task belongs to a cgroup with minimal timer slack value higher than > > +task's value, cgroup's value will be applied. > > + > > +Timer slack controller allows to implement setting timer slack value of > > +a process based on a policy. For example, you can create foreground and > > +background cgroups and move tasks between them based on system state. > > (quoting myself from last time) > > Why do we need a cgroup for this as opposed to (say) inheritance over > fork(), or a system-wide knob, or a per-process/threadgroup knob, or > just leaving the existing code as-is? Presumably you felt that a > cgroup approach is better for manageability, but you didn't tell us > about this and you didn't explore alternative ways of solving the > problem-which-you-didn't-describe. The main goal is reducing wakeups without affecting user experience. Only userspace knows which tasks are important for UX. So we needed a mechanism to define a policy in userspace. Currently timer slack value inheritance over fork(). System-wide/threadgroup knob doesn't allow to change timer slack value of a particular process. It's needed for foreground/background use-case. With per-process know we have to reinvent grouping of tasks in userspace. cgroups is a good solution for it, from my point of view. > > I'm still having trouble seeing why we should merge this. Who will use > it, and for what reason and what benefits will they see? Quantified > benefits, if possible! > -- Kirill A. Shutemov _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
