On Fri, 5 Jun 2015, Alan Stern wrote:
> On Fri, 5 Jun 2015, Mark Hills wrote:
>
> > I have a new USB 3.0 hard drive which appears to be throttled at
> > approx 5Mbyte/sec.
> >
> > Is there a mystery kernel option that is required to enable full
> > performance on these new drives?
> >
> > I have tried changing following:
> >
> > * Switching onboard USB 2.0 interfaces for a completely new USB 3.0
> > interface (xhci_pci)
> >
> > * Enabling and disabling the "USB attached SCSI" CONFIG_USB_UAS
> >
> > But drive performance stays limited at 5Mbyte/sec.
> >
> > I've settled on using the USB 3.0 interface, and the dmesg (below) reports
> > "SuperSpeed" and looks ok.
[...]
> By any chance, do you mount the filesystem with the "-o sync" option?
> That will slow things _way_ down.
It's not -- and also I can reproduce the results with no file system;
just a 'dd' to /dev/sdc1.
> If that's not the answer, try acquiring usbmon traces on the fast and
> slow systems for comparison (see the instructions in
> Documentation/usb/usbmon.txt.).
Thanks for this -- I made some progress.
I also tested reads this time which were ok (150Mbyte/sec), it's only
writes that appear to be throttled.
I have a sample of reads and writes from both systems below. I disabled
'uas' for the tests, droped caches etc. and used 'dd bs=1M' to the
partition.
The most striking thing is that the affected system consistently uses ~4KB
URBs ("Len: 1"?) for writes.
Whereas all the other requests seem to be a majority ~60KB URBs and "Len:
30"
I can imagine this accounts for the lack of throughput, but not whether
it's the cause or a symptom.
The lsusb output for the device is identical on both systems (see below)
I imagine something lies in the code that generates the write requests,
but I am starting from scratch here. I'd be greateful if you (or anyone
else) has information that could point me to the next step.
Thanks
--
Mark
#
# reads on the affected system
#
1 0.000000 4.1 -> host USBMS 77
2 0.000020 host -> 4.2 USBMS 95 SCSI: Read(10) LUN: 0x00 (LBA: 0x000323c0, Len: 30)
3 0.000040 4.2 -> host USB 64 URB_BULK out
4 0.000047 host -> 4.1 USB 64 URB_BULK in
5 0.000642 4.1 -> host USB 61504 URB_BULK in
6 0.000689 host -> 4.1 USB 64 URB_BULK in
7 0.000702 4.1 -> host USBMS 77
8 0.000722 host -> 4.2 USBMS 95 SCSI: Read(10) LUN: 0x00 (LBA: 0x000323de, Len: 2)
9 0.000744 4.2 -> host USB 64 URB_BULK out
10 0.000755 host -> 4.1 USB 64 URB_BULK in
11 0.000811 4.1 -> host USB 8256 URB_BULK in
12 0.000827 host -> 4.1 USB 64 URB_BULK in
13 0.000854 4.1 -> host USBMS 77
14 0.000879 host -> 4.2 USBMS 95 SCSI: Read(10) LUN: 0x00 (LBA: 0x000323e0, Len: 30)
15 0.000895 4.2 -> host USB 64 URB_BULK out
16 0.000906 host -> 4.1 USB 64 URB_BULK in
#
# writes on the affected system <------- this is the 'bad' case
#
1 0.000000 host -> 4.2 USBMS 95 SCSI: Write(10) LUN: 0x00 (LBA: 0x000017fc, Len: 1)
2 0.000019 4.2 -> host USB 64 URB_BULK out
3 0.000026 host -> 4.2 USB 4160 URB_BULK out
4 0.000074 4.2 -> host USB 64 URB_BULK out
5 0.000089 host -> 4.1 USB 64 URB_BULK in
6 0.000147 4.1 -> host USBMS 77
7 0.000955 host -> 4.2 USBMS 95 SCSI: Write(10) LUN: 0x00 (LBA: 0x000017fd, Len: 1)
8 0.000969 4.2 -> host USB 64 URB_BULK out
9 0.000978 host -> 4.2 USB 4160 URB_BULK out
10 0.001027 4.2 -> host USB 64 URB_BULK out
11 0.001034 host -> 4.1 USB 64 URB_BULK in
12 0.001095 4.1 -> host USBMS 77
13 0.001960 host -> 4.2 USBMS 95 SCSI: Write(10) LUN: 0x00 (LBA: 0x000017fe, Len: 1)
14 0.001979 4.2 -> host USB 64 URB_BULK out
15 0.001988 host -> 4.2 USB 4160 URB_BULK out
16 0.002041 4.2 -> host USB 64 URB_BULK out
[... continues, always using "Len: 1" and 4160 size]
#
# reads on the 'good' system
#
1 0.000000 4.1 -> host USB 61504 URB_BULK in
2 0.000020 host -> 4.1 USB 64 URB_BULK in
3 0.000042 4.1 -> host USBMS 77
4 0.000100 host -> 4.2 USBMS 95 SCSI: Read(10) LUN: 0x00 (LBA: 0x0003ab7e, Len: 2)
5 0.000113 4.2 -> host USB 64 URB_BULK out
6 0.000116 host -> 4.1 USB 64 URB_BULK in
7 0.000170 4.1 -> host USB 8256 URB_BULK in
8 0.000174 host -> 4.1 USB 64 URB_BULK in
9 0.000213 4.1 -> host USBMS 77
10 0.000225 host -> 4.2 USBMS 95 SCSI: Read(10) LUN: 0x00 (LBA: 0x0003ab80, Len: 30)
11 0.000251 4.2 -> host USB 64 URB_BULK out
12 0.000254 host -> 4.1 USB 64 URB_BULK in
13 0.000987 4.1 -> host USB 61504 URB_BULK in
14 0.001004 host -> 4.1 USB 64 URB_BULK in
15 0.001030 4.1 -> host USBMS 77
16 0.001056 host -> 4.2 USBMS 95 SCSI: Read(10) LUN: 0x00 (LBA: 0x0003ab9e, Len: 2)
#
# writes on the 'good' system
#
1 0.000000 4.2 -> host USB 64 URB_BULK out
2 0.000007 host -> 4.1 USB 64 URB_BULK in
3 0.000041 4.1 -> host USBMS 77
4 0.000072 host -> 4.2 USBMS 95 SCSI: Write(10) LUN: 0x00 (LBA: 0x0009ed09, Len: 30)
5 0.000084 4.2 -> host USB 64 URB_BULK out
6 0.000089 host -> 4.2 USB 61504 URB_BULK out
7 0.000702 4.2 -> host USB 64 URB_BULK out
8 0.000708 host -> 4.1 USB 64 URB_BULK in
9 0.000744 4.1 -> host USBMS 77
10 0.000800 host -> 4.2 USBMS 95 SCSI: Write(10) LUN: 0x00 (LBA: 0x0009ed27, Len: 30)
11 0.000813 4.2 -> host USB 64 URB_BULK out
12 0.000819 host -> 4.2 USB 61504 URB_BULK out
13 0.001420 4.2 -> host USB 64 URB_BULK out
14 0.001425 host -> 4.1 USB 64 URB_BULK in
15 0.001443 4.1 -> host USBMS 77
16 0.001475 host -> 4.2 USBMS 95 SCSI: Write(10) LUN: 0x00 (LBA: 0x0009ed45, Len: 30)
#
# lsusb output for the device
#
Bus 004 Device 005: ID 0bc2:a0a4 Seagate RSS LLC Backup Plus Desktop Drive
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 3.00
bDeviceClass 0 (Defined at Interface level)
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 9
idVendor 0x0bc2 Seagate RSS LLC
idProduct 0xa0a4 Backup Plus Desktop Drive
bcdDevice 1.00
iManufacturer 2 Seagate
iProduct 3 Backup+ Desk Mac
iSerial 1 NA5R1K71
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 121
bNumInterfaces 1
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 36mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 80 Bulk-Only
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 15
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 15
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 1
bNumEndpoints 4
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 98
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 15
MaxStreams 32
Data-in pipe (0x03)
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 15
MaxStreams 32
Data-out pipe (0x04)
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 15
MaxStreams 32
Status pipe (0x02)
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x04 EP 4 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0400 1x 1024 bytes
bInterval 0
bMaxBurst 0
Command pipe (0x01)
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
wSpeedsSupported 0x000e
Device can operate at Full Speed (12Mbps)
Device can operate at High Speed (480Mbps)
Device can operate at SuperSpeed (5Gbps)
bFunctionalitySupport 1
Lowest fully-functional device speed is Full Speed (12Mbps)
bU1DevExitLat 10 micro seconds
bU2DevExitLat 2047 micro seconds
Device Status: 0x000d
Self Powered
U1 Enabled
U2 Enabled
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