[Dev] Tizen use of FIFO & Nice

Stoppa, Igor igor.stoppa at intel.com
Thu Dec 12 20:18:43 GMT 2013

But AFAIK most of those updates are really trivial to handle.
Usually what really generates lots of inputs is a speed sensor [1]
Which only requires the bumping of a counter in the irq handler.
Filtering and conditioning is done at much lower frequency and with
built in low-pass functions.

Or the source can be some other equally trivial-to-handle signal.

Everything else, which refers to physical measurements, tends to have very
slow dynamic (slow compared to thousands of samples per second =)

And even the reporting of speed is such that it generally has quite
high tolerance to errors in the reporting (higher tolerance at higher
speeds, up to 10-15%)

As long as the value reported is always higher than the effective one =)

I would also assume that nothing mission-critical is controlled by an IVI.

cheers, igor

[1] http://repairpal.com/abs-wheel-speed-sensor

On 12 December 2013 22:01, Clark, Joel <joel.clark at intel.com> wrote:

> For IVI, we are expecting several thousand sensor updates per second, with
> nearly 200 different types of sensor data.  Think about data on the engine,
> transmission, wheels, brakes, windows, doors, seats, radar updates on
> proximity, etc.
> Regards
> Joel
> -----Original Message-----
> From: Kok, Auke-jan H [mailto:auke-jan.h.kok at intel.com]
> Sent: Thursday, December 12, 2013 11:35 AM
> To: Clark, Joel
> Cc: dev at lists.tizen.org
> Subject: Re: [Dev] Tizen use of FIFO & Nice
> On Thu, Dec 12, 2013 at 9:38 AM, Clark, Joel <joel.clark at intel.com> wrote:
> > Why does Tizen use FIFO and NICE?  There are more than 500 threads
> > with FIFO and NICE affecting the performance of critical elements for
> > reading sensor data and updating location etc.
> Mostly to prioritize screen update refresh rates. Do you really need your
> GPS location to update within a 20ms interval?
> Humans can see a single frame drop, easily. Audio is critical too.
> Sensor data (apart from touch) is almost irrelevant at the scale that
> humans can detect.
> Also, even with Nice values set high, applications can still be low
> latency. They do not necessarily conflict.
> Auke
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> Dev at lists.tizen.org
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cheers, igor
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