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[v3,0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

Message ID 20180809093307.6001-1-matwey@sai.msu.ru (mailing list archive)
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Series media: usb: pwc: Don't use coherent DMA buffers for ISO transfer | expand

Message

Matwey V. Kornilov Aug. 9, 2018, 9:33 a.m. UTC 
From: "Matwey V. Kornilov" <matwey.kornilov@gmail.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 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 | 54 +++++++++++++++++++++++++++--------
 include/trace/events/pwc.h     | 64 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+), 12 deletions(-)
 create mode 100644 include/trace/events/pwc.h