linux-kernel - Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC

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Date:	Tue, 12 Apr 2016 08:05:16 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	"Bill Huey (hui)" <bill.huey@...il.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dario Faggioli <raistlin@...ux.it>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Thomas Gleixner <tglx@...utronix.de>,
	KY Srinivasan <kys@...rosoft.com>,
	Amir Frenkel <frenkel.amir@...il.com>,
	Bdale Garbee <bdale@....com>
Subject: Re: [PATCH RFC v0 00/12] Cyclic Scheduler Against RTC

On Mon, 2016-04-11 at 22:59 -0700, Bill Huey (hui) wrote:
> 
> 
> On Mon, Apr 11, 2016 at 10:58 PM, Mike Galbraith <umgwanakikbuti@...il.com> wrote:
> > On Mon, 2016-04-11 at 22:29 -0700, Bill Huey (hui) wrote:
> > > Hi,
> > >
> > > This a crude cyclic scheduler implementation. It uses SCHED_FIFO tasks
> > > and runs them according to a map pattern specified by a 64 bit mask. Each
> > > bit corresponds to an entry into an 64 entry array of
> > > 'struct task_struct'. This works single core CPU 0 only for now.
> > >
> > > Threads are 'admitted' to this map by an extension to the ioctl() via the
> > > of (rtc) real-time clock interface. The bit pattern then determines when
> > > the task will run or activate next.
> > >
> > > The /dev/rtc interface is choosen for this purpose because of its
> > > accessibilty to userspace. For example, the mplayer program already use
> > > it as a timer source and could possibly benefit from being sync to a
> > > vertical retrace interrupt during decoding. Could be an OpenGL program
> > > needing precisely scheduler support for those same handling vertical
> > > retrace interrupts, low latency audio and timely handling of touch
> > > events amognst other uses.
> > 
> > Sounds like you want SGI's frame rate scheduler.

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