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[v5,0/2] media: usb: pwc: Don't use coherent DMA buffers for ISO transfer

Message ID 20180821170629.18408-1-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. 21, 2018, 5:06 p.m. UTC 
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 v4:
 * fix fields order in trace events 
 * minor style fixes

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 | 64 ++++++++++++++++++++++++++++++++---------
 include/trace/events/pwc.h     | 65 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+), 13 deletions(-)
 create mode 100644 include/trace/events/pwc.h