usb 3.0 thumb drive speed limit

[Ian Smith]

On Mon, 2 Jan 2017 12:59:49 +0300, Marat N.Afanasyev wrote:
 > Ian Smith wrote:
 > > On Mon, 2 Jan 2017 11:27:49 +0300, Marat N.Afanasyev wrote:
 > >   > I wonder is there a speed limit on usb 3.0? I've bought
 > >   >
 > >   > ugen0.4: <SanDisk> at usbus0
 > >   > umass2 on uhub7
 > >   > umass2: <SanDisk Extreme, class 0/0, rev 2.10/0.10, addr 4> on usbus0
 > >   > da2 at umass-sim2 bus 2 scbus9 target 0 lun 0
 > >   > da2: <SanDisk Extreme 0001> Removable Direct Access SPC-4 SCSI device
 > >   > da2: Serial Number AA010808161609220143
 > >   > da2: 40.000MB/s transfers
 > >   > da2: 59840MB (122552320 512 byte sectors)
 > >   > da2: quirks=0x2<NO_6_BYTE>
 > >   >
 > >   > that claims 'Up to 245 MBytes/sec read speed'
 > >   >
 > >   > and dd shows:
 > >   >
 > >   > % dd if=/dev/da2 of=/dev/null bs=1m count=1000
 > >   > 1000+0 records in
 > >   > 1000+0 records out
 > >   > 1048576000 bytes transferred in 25.688997 secs (40818098 bytes/sec)
 > >   >
 > >   > why we have such a limit?
 > > 
 > > Seems you've plugged it into a USB 2 port, not USB 3
 > > 
 > > At least you're getting full USB 2 performance (40MB/s)
 > > 
 > > Check if you have one or more USB 3 ports with 'dmesg | grep xhci'

 > afair, single usb 2.0 device can be as fast as 240 Mbits/sec, not 320
 > Mbits/sec:
 > 
 > % dd if=/dev/da2 of=/dev/null bs=1m count=1000
 > 1000+0 records in
 > 1000+0 records out
 > 1048576000 bytes transferred in 34.026227 secs (30816699 bytes/sec)
 > 
 > it's the same drive in usb 2.0 port

Ah, guess I've been taking "40.000MB/s transfers" for USB2 at its word.

Testing 3 USB2 sticks in a USB2 port on my X200 (2.4GHz Core2Duo) I only 
get about 18-20MB/s read for bs=1M count=1k, with little load although 
3k IRQ/s and 10k context switches/s, so I thought yours was good :)

 > And I do have usb 3.0:
 > 
 > % grep xhci /var/run/dmesg.boot
 > xhci0: <XHCI (generic) USB 3.0 controller> mem 0xfeaf8000-0xfeafffff irq 17
 > at device 0.0 on pci5
 > xhci0: 64 bytes context size, 64-bit DMA
 > usbus0 on xhci0
 > xhci0: <XHCI (generic) USB 3.0 controller> mem 0xfeaf8000-0xfeafffff irq 17
 > at device 0.0 on pci5
 > xhci0: 64 bytes context size, 64-bit DMA
 > usbus0 on xhci0
 > 
 > and I tried this thumb drive is in usb 3.0 port first, of course.

Sorry for the static, I know nothing .. and running now unsupported 9.3

cheers, Ian