linux-kernel - Re: [PATCH v2] staging: vc04_services: Replace dmac_map_area with dmac_map

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Date:   Wed, 26 Oct 2016 08:49:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Michael Zoran <mzoran@...wfest.net>
Cc:     devel@...verdev.osuosl.org, daniels@...labora.com,
        swarren@...dotorg.org, lee@...nel.org,
        linux-kernel@...r.kernel.org, noralf@...nnes.org,
        linux-rpi-kernel@...ts.infradead.org, popcornmix@...il.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] staging: vc04_services: Replace dmac_map_area with
 dmac_map_sg

On Tue, Oct 25, 2016 at 07:23:27PM -0700, Michael Zoran wrote:
> 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.
> 
> "Normal" messages sizes should be about 1MB which is beyond
> the length that this change shows a speed increase.
> 
> This is v2 of the patch which includes extra WARN_ONs and
> incorporates feedback from Eric Anholt <eric@...olt.net>.
> 
> Signed-off-by: Michael Zoran <mzoran@...wfest.net>
> ---
>  .../interface/vchiq_arm/vchiq_2835_arm.c           | 152 +++++++++++++--------
>  1 file changed, 93 insertions(+), 59 deletions(-)

Nice work!

I'd like to get an ack from Eric before applying it...

thanks,

greg k-h