[linux-dvb] Re: Alternative v4 demux API

[Holger Waechtler <holger@convergence.de>]

one more remark that came to my mind:

Holger Waechtler wrote:
> Michael Hunold wrote:
>
> > But before thinking about this, someone should really investigate if 
> > these memcpy()s are *really* a problem for system performance. Sure, 
> > there is a lot of copying going on, but I guess that most of the 
> > *real* performance is eaten somewhere else.
>
> This actually depends on the platform you are talking about, not? In any 
> case you want to use accelerating and power-saving hardware on embedded 
> platforms where available, the CPU can probably always do better things 
> than just copying bytes around. It's the same as for your harddisk - you 
> don't want to use PIO if DMA is available, right? PIO is nothing else 
> than copying memory byte-by-byte using the CPU to the IDE bus.
The more serious issue is memory bandwidth: if you use DMA bursts you 
need in most cases only a little more than roughly half the bus 
bandwidth than byte-by-byte transfers. Check the memory and processor 
timing datasheets and compare single-word transfers to burst transfers 
to get more concrete numbers.

Holger



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