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Re: [Discuss-gnuradio] FIFO latency

From: Alexander Chemeris
Subject: Re: [Discuss-gnuradio] FIFO latency
Date: Sun, 29 May 2011 12:22:21 +0400

On Sun, May 29, 2011 at 03:05, Marcus D. Leech <address@hidden> wrote:
> On 05/28/2011 04:28 PM, Alexander Chemeris wrote:
>>> So, while this method is simple and good for non-realtime
>>> applications, it doesn't fit our needs. It may be usable for PHY<->MAC
>>> interaction, but even here I'm not sure it would work well.
>>> PS I test on Core 2 Duo 1.6 GHz with all the GUI stuff running.
>> Ok, setting CPU affinity and cutting off startup artifacts definitely
>> helps.
>> Results are in attachment.
>> Still you can see quite some uncertainty.
> OK, so a roughly 3:1 improvement in peak latency, and somewhat better
> predicability.
> But I'd still counter-assert, to your assertion, that latencies in the
> 10s-of-usec are entirely acceptable for
>  a wide-range of "real-time" applications, even with occasional latency
> excursions that increase the variability
>  by 50:1 or so.
> I can well imagine that they aren't acceptable for *your* application.  I
> mean, if all applications were the same, it would
>  be a very boring world, with most of us working at fast-food restaurants
> :-)
> But I'll stand by my original suggestion that use of FIFOs are an acceptable
> technique for a wide variety of applications, including
>  "real-time" applications, depending on constraints and requirements.

Sure, I don't say that no one should use queues :)
I just want to say that it may not be suitable for applications with
more tight requirements - i.e. some alternative may be needed.

But to say truth - I'm surprised by their performance, I thought it
would be much worse. So it may be a good starting point from which we
could refine later.

Alexander Chemeris.

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