Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> 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.balbi@xxxxxxxxxxxxxxx>
>> ---
>> 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?
you mean that a USB3 device with US_FL_MAX_SECTORS* should still respect
the 64 limit ? yeah I can do that. I'll send a new version tomorrow (so
I can wait for confirmation from you)
--
balbi
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