2 Nov 2011 17:35
Timer Slack Controller
From http://lwn.net/Articles/463357/ The "timer slack controller" is a proposed mechanism that would allow a session management program to adjust the timer tolerances of a group of processes with a single knob. It seems like a relatively obscure and harmless feature, but it has been the focus of an intense debate on the kernel mailing lists. The core question has been seen before: what measures should the kernel take, if any, to keep poorly-written applications from hurting performance? Timers allow a process to request a wakeup at some future time; timer slack gives the kernel some leeway in its implementation of those timers. If the kernel can delay specific timers by a bounded amount, it can often expire multiple timers at once, minimizing the number of wakeups and, thus, reducing the system's power consumption. Some processes need more precise timing than others; for this reason, the kernel allows a process to specify its maximum timer slack with the prctl() system call. There is, currently, no mechanism to allow one process to adjust another process's timer slack value; it is generally assumed that any given process knows best when it comes to its own timing requirements. The timer slack controller allows a suitably privileged process to set the timer slack value for every process contained within a control group. The patch has been circulating for some time without generating a great deal of interest; it recently resurfaced in response to the "plumber's wish list for Linux" which requested such a feature. ............. ______________________________________(Continue reading)
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