u盘速度

怎么⽤dd命令测试U盘读写速度

1.如何确认host是将外设识别为2.0还是3.0

a)关注dmesg，查看如下字串

usb2-1:newSuperSpeedUSBdevicenumber2usingxhci-hcd

说明是识别为3.0的外设

usb2-1:newhigh-speedUSBdevicenumber2usingxhci-hcd

说明是识别为2.0的外设

b)关注/sys/bus/usb/devices/usbX/下⾯的speed字段是480还是5000

2.U盘的读写速率测试

cd/mnt/runtime/default/5035-D1BD

写⼊速度测试：

msm8953_64:/mnt/runtime/read/5035-D1BD#ddif=/dev/zeroof=./=1024576count=256

256+0recordsin

256+0recordsout

262291456bytestransferredin5.136cs(51069208bytes/c)

读取速度测试

msm8953_64:/mnt/runtime/default/5035-D1BD#ddif=./=/dev/nullbs=1024576

256+0recordsin

256+0recordsout

262291456bytestransferredin9.204cs(28497550bytes/c)

3.每次读取和写⼊前需要执⾏dropcache

echo3>/proc/sys/vm/drop_caches