On Tue, 2016-06-07 at 13:04 +0300, Andy Shevchenko wrote: > > I'll find some time to look at both a short stream and a long > stream, > > based on the branch you've indicated and maybe against the latest > > stable kernel. > > Please, do. I'm planning to resend new version soon (this week or > lately beginning of the next one). So. Generally DMA appears to make little-to-no difference here. With small data sets, 128 bytes in the test case - there appears to be a slight performance gain at lower BAUD rates, however for small data-sets and large data sets 32k for the large test case, there appears to be a performance penalty at higher BAUD rates. One thing I have noticed is that the following never completes and can't be reset back to mode=0 or mode=3 to restore functionality - definitely worth looking at if you are spinning another patch. ### never completes #### root@galileo:~# echo 1 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# stty -F /dev/ttyS0 921600 root@galileo:~# time cat tester.txt > /dev/ttyS0 ### never completes #### Performance data set root@galileo:~# dmesg > tester.txt root@galileo:~# ls -las tester.txt 32 -rw-r--r-- 1 root root 32300 Jan 1 2001 tester.txt #### With DMA on @ 926100 32k file #### root@galileo:~# echo 0 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# stty -F /dev/ttyS0 921600 root@galileo:~# time cat tester.txt > /dev/ttyS0 real 0m0.421s user 0m0.010s sys 0m0.000s ### With NoDMA on @ 926100 32k file #### root@galileo:~# echo 3 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# stty -F /dev/ttyS0 921600 root@galileo:~# time cat tester.txt > /dev/ttyS0 real 0m0.421s user 0m0.020s sys 0m0.000s #### With DMA on @ 9600 32k file #### root@galileo:~# echo 0 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# stty -F /dev/ttyS0 9600 root@galileo:~# time cat tester.txt > /dev/ttyS0 real 0m34.381s user 0m0.000s sys 0m0.010s #### With NoDMA on @ 9600 32k file ##### root@galileo:~# echo 3 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# stty -F /dev/ttyS0 9600 root@galileo:~# time cat tester.txt > /dev/ttyS0 real 0m34.391s user 0m0.010s sys 0m0.000s root@galileo:~# ls -las tester_small.txt 4 -rw-r--r-- 1 root root 128 Jan 1 00:06 tester_small.txt ### With DMA on @ 921600 128 byte test file ### root@galileo:~# stty -F /dev/ttyS0 921600 root@galileo:~# echo 0 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# time cat tester_small.txt > /dev/ttyS0 real 0m0.031s user 0m0.010s sys 0m0.000s ### With NoDMA on @ 921600 128 byte test file ### root@galileo:~# stty -F /dev/ttyS0 921600 root@galileo:~# echo 3 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# time cat tester_small.txt > /dev/ttyS0 real 0m0.013s user 0m0.010s sys 0m0.000s ### With DMA on @ 9600 128 byte test file ### root@galileo:~# stty -F /dev/ttyS0 9600 root@galileo:~# echo 0 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# time cat tester_small.txt > /dev/ttyS0 real 0m0.161s user 0m0.000s sys 0m0.010s ### With NoDMA on @ 9600 128 byte test file ### root@galileo:~# stty -F /dev/ttyS0 9600 root@galileo:~# echo 3 > /sys/class/tty/ttyS0/dma_mode root@galileo:~# time cat tester_small.txt > /dev/ttyS0 real 0m0.161s user 0m0.000s sys 0m0.000s --- bod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
