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 3.3 times speedup. Changes since v5: * add dma_sync_single_for_device() as required by Laurent Pinchart 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 | 69 ++++++++++++++++++++++++++++++++++-------- include/trace/events/pwc.h | 65 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 121 insertions(+), 13 deletions(-) create mode 100644 include/trace/events/pwc.h -- 2.16.4
