我在Linux下的USB 3.0速度有问题。我正在测试以下部分：
- “NEC公司uPD720200 USB 3.0主机控制器”（pcie）
- “Pretec 240”USB 3.0读卡器
- Sandisk Extreme Compact Flash 60 MB / s
在Windows 7中，“HD-Tune Pro”报告的读取速度为60-70 MB / s， 但在Linux中“hdparm -t”/“dd if = / dev / sdX of = / dev / null”仅报告大约25-30 MB / s。
uname -a
Linux workstation 3.1-0.slh.2-aptosid-amd64 #1 SMP PREEMPT Tue Oct 25 01:47:47 UTC 2011 x86_64 GNU/Linu
连接读卡器时/ var / log / syslog：
Nov 3 19:20:33 localhost kernel: [ 1973.293522] usb 4-1: new SuperSpeed USB device number 10 using xhci_hcd
Nov 3 19:20:33 localhost kernel: [ 1973.314354] xhci_hcd 0000:06:00.0: WARN: short transfer on control ep
Nov 3 19:20:33 localhost kernel: [ 1973.346584] xhci_hcd 0000:06:00.0: WARN: short transfer on control ep
Nov 3 19:20:33 localhost kernel: [ 1973.375744] xhci_hcd 0000:06:00.0: WARN: short transfer on control ep
Nov 3 19:20:33 localhost kernel: [ 1973.404950] xhci_hcd 0000:06:00.0: WARN: short transfer on control ep
Nov 3 19:20:33 localhost kernel: [ 1973.405189] usb 4-1: New USB device found, idVendor=0bda, idProduct=0301
Nov 3 19:20:33 localhost kernel: [ 1973.405195] usb 4-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Nov 3 19:20:33 localhost kernel: [ 1973.405199] usb 4-1: Product: USB3.0 Card Reader
Nov 3 19:20:33 localhost kernel: [ 1973.405202] usb 4-1: Manufacturer: Realtek
Nov 3 19:20:33 localhost kernel: [ 1973.405206] usb 4-1: SerialNumber: 201006010301
Nov 3 19:20:33 localhost mtp-probe: checking bus 4, device 10: "/sys/devices/pci0000:00/0000:00:1c.4/0000:06:00.0/usb4/4-1"
Nov 3 19:20:33 localhost kernel: [ 1973.408167] xhci_hcd 0000:06:00.0: WARN: short transfer on control ep
Nov 3 19:20:33 localhost kernel: [ 1973.411443] xhci_hcd 0000:06:00.0: WARN: short transfer on control ep
Nov 3 19:20:33 localhost kernel: [ 1973.412056] scsi15 : usb-storage 4-1:1.0
Nov 3 19:20:34 localhost mtp-probe: bus: 4, device: 10 was not an MTP device
Nov 3 19:20:35 localhost kernel: [ 1974.429746] scsi 15:0:0:0: Direct-Access Generic- USB3.0 CRW-CF/MD 1.00 PQ: 0 ANSI: 0 CCS
Nov 3 19:20:35 localhost kernel: [ 1974.445740] scsi 15:0:0:1: Direct-Access Generic- USB3.0 CRW-SM/xD 1.00 PQ: 0 ANSI: 0 CCS
Nov 3 19:20:35 localhost kernel: [ 1974.462208] scsi 15:0:0:2: Direct-Access Generic- USB3.0 CRW-SD 1.00 PQ: 0 ANSI: 0 CCS
Nov 3 19:20:35 localhost kernel: [ 1974.478117] scsi 15:0:0:3: Direct-Access Generic- USB3.0 CRW-MS 1.00 PQ: 0 ANSI: 0 CCS
Nov 3 19:20:35 localhost kernel: [ 1974.494461] scsi 15:0:0:4: Direct-Access Generic- USB3.0 CRW-SD/MS 1.00 PQ: 0 ANSI: 0 CCS
Nov 3 19:20:35 localhost kernel: [ 1974.495905] sd 15:0:0:0: Attached scsi generic sg3 type 0
Nov 3 19:20:35 localhost kernel: [ 1974.496225] sd 15:0:0:1: Attached scsi generic sg4 type 0
Nov 3 19:20:35 localhost kernel: [ 1974.497412] sd 15:0:0:2: Attached scsi generic sg5 type 0
Nov 3 19:20:35 localhost kernel: [ 1974.497732] sd 15:0:0:3: Attached scsi generic sg6 type 0
Nov 3 19:20:35 localhost kernel: [ 1974.497972] sd 15:0:0:4: Attached scsi generic sg7 type 0
Nov 3 19:20:35 localhost kernel: [ 1975.165150] sd 15:0:0:1: [sde] Attached SCSI removable disk
Nov 3 19:20:35 localhost kernel: [ 1975.168154] sd 15:0:0:0: [sdd] 15625216 512-byte logical blocks: (8.00 GB/7.45 GiB)
Nov 3 19:20:35 localhost kernel: [ 1975.170400] sd 15:0:0:0: [sdd] Write Protect is off
Nov 3 19:20:35 localhost kernel: [ 1975.170406] sd 15:0:0:0: [sdd] Mode Sense: 03 00 00 00
Nov 3 19:20:35 localhost kernel: [ 1975.172895] sd 15:0:0:4: [sdh] Attached SCSI removable disk
Nov 3 19:20:35 localhost kernel: [ 1975.173277] sd 15:0:0:0: [sdd] No Caching mode page present
Nov 3 19:20:35 localhost kernel: [ 1975.173283] sd 15:0:0:0: [sdd] Assuming drive cache: write through
Nov 3 19:20:35 localhost kernel: [ 1975.174211] sd 15:0:0:2: [sdf] Attached SCSI removable disk
Nov 3 19:20:35 localhost kernel: [ 1975.175141] sd 15:0:0:3: [sdg] Attached SCSI removable disk
Nov 3 19:20:35 localhost kernel: [ 1975.183265] sd 15:0:0:0: [sdd] No Caching mode page present
Nov 3 19:20:35 localhost kernel: [ 1975.183271] sd 15:0:0:0: [sdd] Assuming drive cache: write through
Nov 3 19:20:35 localhost kernel: [ 1975.211534] sdd: sdd1
Nov 3 19:20:35 localhost kernel: [ 1975.219096] sd 15:0:0:0: [sdd] No Caching mode page present
Nov 3 19:20:35 localhost kernel: [ 1975.219101] sd 15:0:0:0: [sdd] Assuming drive cache: write through
Nov 3 19:20:35 localhost kernel: [ 1975.219106] sd 15:0:0:0: [sdd] Attached SCSI removable disk
lsusb -v：
Bus 004 Device 010: ID 0bda:0301 Realtek Semiconductor Corp.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 3.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 9
idVendor 0x0bda Realtek Semiconductor Corp.
idProduct 0x0301
bcdDevice 1.20
iManufacturer 1 Realtek
iProduct 2 USB3.0 Card Reader
iSerial 3 201006010301
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 44
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 4 CARD READER
bmAttributes 0x80
(Bus Powered)
MaxPower 200mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 80 Bulk (Zip)
iInterface 5 Bulk-In, Bulk-Out, Interface
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 3
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 3
Binary Object Store Descriptor:
bLength 5
bDescriptorType 15
wTotalLength 22
bNumDeviceCaps 2
USB 2.0 Extension Device Capability:
bLength 7
bDescriptorType 16
bDevCapabilityType 2
bmAttributes 0x00000002
Link Power Management (LPM) Supported
SuperSpeed USB Device Capability:
bLength 10
bDescriptorType 16
bDevCapabilityType 3
bmAttributes 0x00
Latency Tolerance Messages (LTM) Supported
wSpeedsSupported 0x000e
Device can operate at Full Speed (12Mbps)
Device can operate at High Speed (480Mbps)
Device can operate at SuperSpeed (5Gbps)
bFunctionalitySupport 0
Lowest fully-functional device speed is Low Speed (1Mbps)
bU1DevExitLat 1 micro seconds
bU2DevExitLat 2815 micro seconds
Device Status: 0x0000
(Bus Powered)