Re: [Discuss-gnuradio] Question about UHD driver

[Mark McCarron]

I would tend to agree, but if we do not outline what we require from manufacturers, we will never get it.  I would seriously suggest writing a specification and submitting it to Intel, AMD, etc.

Regards,

Mark McCarron

> Date: Fri, 17 May 2013 18:04:37 +0200
> From: address@hidden
> To: address@hidden
> Subject: Re: [Discuss-gnuradio] Question about UHD driver
>
> Hi Mark,
>
> as interesting as your point is, that's not something that
> can be fixed within the scope of GNU Radio or even UHD...
>
> Anyhow, I'm not really convinced that multiple DMA transfers are always
> faster than copying data using memcpy - at least if those DMA transfers
> copy only a few kilobytes, as is the case with packets from network devices.
> The fact that packets are of limited size is not really a problem of
> current computing architectures - it's a consequence of having packet
> networks. Of course, it would be nice if your hardware would be able to
> actually stream data into your userland, that somehow has the (zero
> overhead) capability to tell the hardware to send the next sample - but
> in reality, hardware-to-cpu-transfers usually happen en block, and that
> is just fine for most applications, since there is little use of having
> samples one after another; therefore, some buffering is always necessary
> (and will always be).
> For the sake of adaptivity, hardware supplied data most probably won't
> be written to copy device data to multiple RAM addresses, since the data
> from the device usually needs some processing (hence the driver).
> So in effect, in most imaginable cases a device will do a single
> DMA transfer to RAM.
>
> Greetings,
> Marcus
>
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