content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7BIT
Subject: RE: 2.6.11 timeval_to_jiffies() wrong for ms resolution timers
Date: Wed, 25 May 2005 13:16:45 -0600
Message-ID: <21FFE0795C0F654FAD783094A9AE1DFC07AFE7CD@cof110avexu4.global.avaya.com>
Thread-Topic: 2.6.11 timeval_to_jiffies() wrong for ms resolution timers
Thread-Index: AcVhVLHZkkrv5mMQT4yBzrlxdYAshgABvHZQAACWLzA=
From: "Davda, Bhavesh P \(Bhavesh\)" <bhavesh@avaya.com>
To: "Chris Friesen" <cfriesen@nortel.com>, <george@mvista.com>
Cc: <linux-kernel@vger.kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 3170
Lines: 95

Awefully sorry about the line-breaks (or absence thereof!)

Stupid Outlook that corporate IT forces us to use!

And I meant 20 ms, not 20 us, of course...

- Bhavesh

Bhavesh P. Davda | Distinguished Member of Technical Staff | Avaya |
1300 West 120th Avenue | B3-B03 | Westminster, CO 80234, U.S.A. |
Voice/Fax: (303) 538-4438 | bhavesh@avaya.com

 

> -----Original Message-----
> From: Davda, Bhavesh P (Bhavesh) 
> Sent: Wednesday, May 25, 2005 1:07 PM
> To: 'Chris Friesen'; 'george@mvista.com'
> Cc: 'linux-kernel@vger.kernel.org'
> Subject: RE: 2.6.11 timeval_to_jiffies() wrong for ms 
> resolution timers
> 
> > -----Original Message-----
> > From: Chris Friesen [mailto:cfriesen@nortel.com] 
> > Sent: Wednesday, May 25, 2005 12:08 PM
> > To: george@mvista.com
> > Cc: Davda, Bhavesh P (Bhavesh); linux-kernel@vger.kernel.org
> > Subject: Re: 2.6.11 timeval_to_jiffies() wrong for ms 
> > resolution timers
> > 
> > George Anzinger wrote:
> > > Chris Friesen wrote:
> > 
> > >> What about telling it to wake up a jiffy earlier, then checking 
> > >> whether the scheduling lag was enough to cause it to have 
> > waited the 
> > >> full specified time.  If not, put it to sleep for another jiffy.
> > 
> > > The user is, of course, free to do what ever they would like.  
> > 
> > I actually meant doing this in the kernel.
> 
> Ditto.
> 
> > 
> >  > For a
> > > more complete solution you might be interested in HRT (High Res 
> > > Timers).  See my signature below.
> > 
> > Yep.  One more patch to apply and worry about versions and 
> > maintenance. 
> >   Not enough of a demand for us to be able to use it, at 
> > least at this 
> > point.
> > 
> > Chris
> 
> Ditto ditto :)
> 
> BTW, this reminds me an aweful lot of TH2GT2G, and Deep 
> Thought taking 7.5 million years to come up with the answer "42!"
> 
> Me: Hey Deep Thought! What's 20 us converted into jiffies?
> 
> Deep Thought: Let's see: after accounting for all kinds of 
> underflow and overflow possibilities, and extending the 
> operands to 64-bit to retain the best precision, and 
> crunching through a few complex macros, the answer you're 
> looking for is... Is... Is... "21!" The real problem is: You 
> didn't ask me the right question. You should have asked me 
> "What's 19 us converted into jiffies?"
> 
> On a more serious note: what is a real-time (read 
> SCHED_FIFO/SCHED_RR) task to use to get millisecond accuracy 
> wakeup timing services from the kernel? i.e. what are the 
> alternatives to setitimer() that wake up the task exactly at 
> the interval that is requested of it? You mention high-res 
> timers as a possibility, but in the form of a patch. What's 
> available in mainline unpatched?
> 
> Thanks
> 
> - Bhavesh
> 
> 
> 
> Bhavesh P. Davda | Distinguished Member of Technical Staff | Avaya |
> 1300 West 120th Avenue | B3-B03 | Westminster, CO 80234, U.S.A. |
> Voice/Fax: (303) 538-4438 | bhavesh@avaya.com 
> 
-
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/