linux-kernel - RE: [RFC] Dynamic Tick and Deferrable Timer Support

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Message-ID: <7B4574D56E4ADF438756313E9A172A87319DD3DC@dlee01.ent.ti.com>
Date:	Wed, 8 Apr 2009 14:20:54 -0500
From:	"Hunter, Jon" <jon-hunter@...com>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronics.de>
Subject: RE: [RFC] Dynamic Tick and Deferrable Timer Support



> -----Original Message-----
> From: Pallipadi, Venkatesh [mailto:venkatesh.pallipadi@...el.com]
> Sent: Tuesday, January 27, 2009 12:36 PM
> To: Hunter, Jon
> Cc: Andrew Morton; linux-kernel@...r.kernel.org; Thomas Gleixner
> Subject: RE: [RFC] Dynamic Tick and Deferrable Timer Support
> 
> On Mon, 2009-01-26 at 13:41 -0800, Hunter, Jon wrote:
> > Pallipadi, Venkatesh <mailto:venkatesh.pallipadi@...el.com> wrote on
> Monday, January 26, 2009 1:48 PM:
> >
> > > I looked at your patch earlier, but I was concerned about few
> > > things and wanted to spend some more time on it. So, I did
> > > not reply earlier.
> >
> > No problem, I was not sure how clear my original email was :-)
> >
> > > The potential issues I see:
> > > - May be a bit theoritcal, as this may not happen in reality.
> > > But, with your change, if all the timers happen to be
> > > defrrable, timer wheel never advances and none of the timers
> > > expire. Not sure whether we need to handle this cleanly
> > > somehow or assume that not all the timers will be deferrable.
> >
> > So my understanding is, and please correct me if I am wrong, but as long
> as there is a timer interrupt then the timer wheel will advanced and all
> deferred timer functions will get executed. If that is the case then we
> should always be guaranteed a timer interrupt due to the implementation of
> the dynamic tick.
> >
> > The dynamic tick defines a maximum sleep period, max_delta_ns, which is
> a member of the "clock_event_device" structure. This governs the maximum
> time you could be asleep/idle for. Currently, the variable,
> "max_delta_ns", is defined as a 32-bit type (long) and for most
> architectures, if not all, this is configured by calling function
> "clockevent_delta2ns()". The maximum value that "max_delta_ns" can be
Pallipadi, Venkatesh wrote: 

> Ok. Thinking about it a bit more, I think we can push this patch along.
> Thomas/Andrew, can one of you pick up this patch..
> 
> Thanks,
> Venki
> 
> Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
> 

Hi Andrew, Thomas,

Sorry to respond to this old thread, however, I wanted to see if you had any feedback on this patch. Let me know if you would like me to re-post. 

Cheers
Jon