On Fri, 12 Aug 2016, Felipe Balbi wrote: > Alan Stern <st...@rowland.harvard.edu> writes: > > > On Tue, 31 May 2016, Michael Schaller wrote: > > > >> Is there anything else I can do to debug this issue further? > >> Are there any quirks I could try? > >> > >> On Wed, May 18, 2016 at 3:41 PM, Michael Schaller <mi...@google.com> wrote: > >> > [1.] One line summary of the problem: > >> > Slow writes with dd on Lexar JumpDrive P20 64GB flash drives connected > >> > via Intel USB 3.0 host controllers. > > > > Did you ever try increasing the max_sectors_kb value? > > > > /sys/block/sdb/queue/max_sectors_kb will be set to 120 by default, but > > for a USB-3 device you should be able to increase it up to 1024. That > > might give a considerable speedup. > > we're using 2048 sectors by default for USB3 nowadays. See commit > 5b91dfe187bb usb: storage: scsiglue: limit USB3 devices to 2048 sectors
2048 sectors = 1024 KB. I wasn't sure whether the new value for max_hw_sectors_kb also sets the default for max_sectors_kb, but it looks like it does. Also, we should mention that this higher max_hw_sectors_kb limit was added in the 4.7 kernel, which wasn't released until after Michael reported the slow write speeds. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
