On Fri, Oct 14, 2011 at 03:43:48PM -0700, Andrew Morton wrote: > On Tue, 11 Oct 2011 19:15:29 +0300 > "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx> wrote: > > > 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. > > I'm having trouble understanding the value of this feature. Users can > presently control the timer-slack of a group of processes via > inherit-over-fork. > > Perhaps there's a case for providing a way for process A to set process > B's slack. And perhaps B's children. That would be a simpler patch > and would have the considerable advantage that it doesn't require > cgroups. > > So.... why should we merge this? Putting a task to a cgroup isn't change task's timer slack, it may affect "effective timer slack", if min timer slack for the cgroup > task's timer slack. Since we don't touch task's slack value we can drag tasks between cgroups and always get the most relaxed slack value for a task without saving/restoring it in userspace. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
