linux-kernel - [PATCH 0/2] Fix remaining arm64 build issues in vchiq

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Date:   Sun, 23 Oct 2016 22:28:50 -0700
From:   mzoran@...wfest.net
To:     gregkh@...uxfoundation.org
Cc:     mzoran@...wfest.net, daniels@...labora.com, eric@...olt.net,
        noralf@...nnes.org, popcornmix@...il.com,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] Fix remaining arm64 build issues in vchiq

From: Michael Zoran <mzoran@...wfest.net>

Hi,

I implemented an alternative implementation of vchiq that uses
dma_map_sg instead of dma_map_page.  I've included some benchmarks.

As you can see that for larger page sizes, the dma_map_sg
implementation is faster then the original unportable dma_map_area
implementation.  So it's really a question of how important is
portability and getting this driver checked into upstream vs.
performance with small message sizes.

(also included in patch 2/2)
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

So 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.

This removes all the errors and all the warnings except:
In file included from drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c:34:0:
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c: In function ‘parse_rx_slots’:
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c:1622:29: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
   DEBUG_VALUE(PARSE_HEADER, (int)header);
                             ^
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h:189:33: note: in definition of macro ‘DEBUG_VALUE’
  do { debug_ptr[DEBUG_ ## d] = (v); dsb(sy); } while (0)

Thanks.


Michael Zoran (2):
  staging: vc04_services: Fix unportable cast in vchiq_copy_from_user
  staging: vc04_services: Replace dmac_map_area with dmac_map_sg

 .../interface/vchiq_arm/vchiq_2835_arm.c           | 155 ++++++++++++---------
 1 file changed, 92 insertions(+), 63 deletions(-)

-- 
2.9.3