linux-kernel - [PATCH v4 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

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Date:   Thu,  9 Aug 2018 21:11:01 +0300
From:   "Matwey V. Kornilov" <matwey@....msu.ru>
To:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     "Matwey V. Kornilov" <matwey.kornilov@...il.com>,
        tfiga@...omium.org, laurent.pinchart@...asonboard.com,
        matwey@....msu.ru, stern@...land.harvard.edu,
        ezequiel@...labora.com, hdegoede@...hat.com, hverkuil@...all.nl,
        mchehab@...nel.org, rostedt@...dmis.org, mingo@...hat.com,
        isely@...ox.com, bhumirks@...il.com, colin.king@...onical.com,
        kieran.bingham@...asonboard.com, keiichiw@...omium.org
Subject: [PATCH v4 0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

From: "Matwey V. Kornilov" <matwey.kornilov@...il.com>

DMA cocherency slows the transfer down on systems without hardware coherent
DMA. In order to demontrate this we introduce performance measurement
facilities in patch 1 and fix the performance issue in patch 2 in order to
obtain 4 times speedup.

Changes since v3:
 * fix scripts/checkpatch.pl errors
 * use __string to store name in trace events

Changes since v2:
 * use dma_sync_single_for_cpu() to achive better performance
 * remeasured performance

Changes since v1:
 * trace_pwc_handler_exit() call moved to proper place
 * detailed description added for commit 1
 * additional output added to trace to track separate frames


Matwey V. Kornilov (2):
  media: usb: pwc: Introduce TRACE_EVENTs for pwc_isoc_handler()
  media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

 drivers/media/usb/pwc/pwc-if.c | 63 ++++++++++++++++++++++++++++++++--------
 include/trace/events/pwc.h     | 65 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+), 12 deletions(-)
 create mode 100644 include/trace/events/pwc.h

-- 
2.16.4