Re: [PATCH 2/2] staging: vc04_services: Replace dmac_map_area with dmac_map_sg

[Greg KH <gregkh@linuxfoundation.org>]

On Sun, Oct 23, 2016 at 10:29:32PM -0700, mzoran@crowfest.net wrote:
> From: Michael Zoran <mzoran@crowfest.net>
> 
> The original arm implementation uses dmac_map_area which is not
> portable.  Replace it with an architecture neutral version
> which uses dma_map_sg.
> 
> As you can see that for larger page sizes, the dma_map_sg
> implementation is faster then the original unportable dma_map_area
> implementation.  
> 
> Test                       dmac_map_area   dma_map_page dma_map_sg
> vchiq_test -b 4 10000      51us/iter       76us/iter    76us
> vchiq_test -b 8 10000      70us/iter       82us/iter    91us
> vchiq_test -b 16 10000     94us/iter       118us/iter   121us
> vchiq_test -b 32 10000     146us/iter      173us/iter   187us
> vchiq_test -b 64 10000     263us/iter      328us/iter   299us
> vchiq_test -b 128 10000    529us/iter      631us/iter   595us
> vchiq_test -b 256 10000    2285us/iter     2275us/iter  2001us
> vchiq_test -b 512 10000    4372us/iter     4616us/iter  4123us
> 
> For message sizes >= 64KB, dma_map_sg is faster then dma_map_page.
> 
> For message size >= 256KB, the dma_map_sg is the fastest
> implementation.

What is the "normal" message size value when using this driver?

thanks,

greg k-h