On Mon, 11 Apr 2016, Felipe Balbi wrote:
> USB3 devices, because they are much newer, have much
> less chance of having issues with larger transfers.
>
> We still keep a limit because anything above 2048
> sectors really rendered negligible speed
> improvements, so we will simply ignore
> that. Transferring 1MiB should already give us
> pretty good performance.
>
> Signed-off-by: Felipe Balbi <felipe.ba...@linux.intel.com>
> ---
> drivers/usb/storage/scsiglue.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
> index 9da1fb3d0ff4..4512cf78a284 100644
> --- a/drivers/usb/storage/scsiglue.c
> +++ b/drivers/usb/storage/scsiglue.c
> @@ -115,13 +115,19 @@ static int slave_configure(struct scsi_device *sdev)
> {
> struct us_data *us = host_to_us(sdev->host);
>
> - /* Many devices have trouble transferring more than 32KB at a time,
> - * while others have trouble with more than 64K. At this time we
> - * are limiting both to 32K (64 sectores).
> - */
> - if (us->fflags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN)) {
> + if (us->pusb_dev->speed >= USB_SPEED_SUPER) {
> + /* USB3 devices will be limited to 2048 sectors. This gives us
> + * better throughput on most devices.
> + */
> + blk_queue_max_hw_sectors(sdev->request_queue, 2048);
> + } else if (us->fflags & (US_FL_MAX_SECTORS_64 | US_FL_MAX_SECTORS_MIN))
> {
> unsigned int max_sectors = 64;
>
> + /* Many devices have trouble transferring more than 32KB at a
> time,
> + * while others have trouble with more than 64K. At this time we
> + * are limiting both to 32K (64 sectores).
> + */
> +
> if (us->fflags & US_FL_MAX_SECTORS_MIN)
> max_sectors = PAGE_SIZE >> 9;
> if (queue_max_hw_sectors(sdev->request_queue) > max_sectors)
I should have noticed this before. If something goes wrong with the
2048-sector limit, this doesn't permit the user to override. Shouldn't
the test for USB_SPEED_SUPER go after the other FL_MAX_SECTORS tests?
Alan Stern
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