Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> writes: > On Sun, Oct 23, 2016 at 10:29:32PM -0700, mzoran@xxxxxxxxxxxx wrote: >> From: Michael Zoran <mzoran@xxxxxxxxxxxx> >> >> The original arm implementation uses dmac_map_area which is not >> portable. Replace it with an architecture neutral version >> which uses dma_map_sg. >> >> As you can see that for larger page sizes, the dma_map_sg >> implementation is faster then the original unportable dma_map_area >> implementation. >> >> 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 >> >> 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. > > What is the "normal" message size value when using this driver? For the contents of a bulk transfer, the performance case you care about is moving an image (video decode, camera, etc.), so on the order of 1MB.
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