Messages in this thread | | | Date | Tue, 27 Mar 2012 17:21:34 +0200 | Subject | Re: [PATCH 11/32] nohz/cpuset: Don't turn off the tick if rcu needs it | From | Gilad Ben-Yossef <> |
| |
On Thu, Mar 22, 2012 at 6:18 PM, Christoph Lameter <cl@linux.com> wrote: > On Thu, 22 Mar 2012, Gilad Ben-Yossef wrote: > >> > Is there any way for userspace to know that the tick is not off yet due to >> > this? It would make sense for us to have busy loop in user space that >> > waits until the OS has completed all processing if that avoids future >> > latencies for the application. >> > >> >> I previously suggested having the user register to receive a signal >> when the tick >> is turned off. Since the tick is always turned off the user task is >> the current task >> by design, *I think* you can simply mark the signal pending when you >> turn the tick off. > > Ok that sounds good. You would define a new signal for this? >
My gut instinct is to let the process register with a specific signal (properly the RT range) it wants to receive when the tick goes off and/or on.
> So we would startup the application. App will do all prep work (memory > allocation, device setup etc etc) and then wait for the signal to be > received. After that it would enter the low latency processing phase. > > Could we also get a signal if something disrupts the peace and switches > the timer interrupt on again? >
I think you'll have to since once you have the tick turned off there is no guarantee that it wont get turned on by a timer scheduling an task or an IPI.
-- Gilad Ben-Yossef Chief Coffee Drinker gilad@benyossef.com Israel Cell: +972-52-8260388 US Cell: +1-973-8260388 http://benyossef.com
"If you take a class in large-scale robotics, can you end up in a situation where the homework eats your dog?" -- Jean-Baptiste Queru -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |