On Mon, Jun 24, 2013 at 9:06 PM, Oliver Neukum <oliver@xxxxxxxxxx> wrote:
> On Monday 24 June 2013 20:58:26 Ming Lei wrote:
>> On Mon, Jun 24, 2013 at 6:24 PM, Oliver Neukum <oliver@xxxxxxxxxx> wrote:
>> > On Monday 24 June 2013 17:42:05 Ming Lei wrote:
>> >> All 4 transfer types can work well on EHCI HCD after switching to run
>> >> URB giveback in tasklet context, so mark all HCD drivers to support
>> >> it.
>> >>
>> >> At the same time, don't release ehci->lock during URB giveback,
>> >> and remove the check on HCD_BH in ehci_disable_event().
>> >>
>> >> From below test results on 3 machines(2 ARM and one x86), time
>> >> consumed by EHCI interrupt handler droped much without performance
>> >> loss.
>> >>
>> >> 1 test description
>> >> 1.1 mass storage performance test:
>> >> - run below command 10 times and compute the average performance
>> >>
>> >> dd if=/dev/sdN iflag=direct of=/dev/null bs=200M count=1
>> >
>> > It would be nice to get worst case numbers. How bad does it get
>> > if you reduce the sg size in usb-storage from 120K to 4K?
>>
>> A quick test on one arm A15 box shows that the average speed over
>> 10 times 'dd' becomes 8.0MB/sec from 8.160MB/sec when 'bs'
>> parameter of 'dd' changes to 4K, so there is ~1.9% performance
>> loss with the patch under the worst case.
>>
>> Same test on my T410(x86), the speed difference is only 40K.
>>
>> I will collect the worst case numbers and include it in the commit
>> log of V3.
>
> Sorry,
>
> I was referring to scsiglue.c
>
> struct scsi_host_template usb_stor_host_template = {
> /* basic userland interface stuff */
> .name = "usb-storage",
> .proc_name = "usb-storage",
> .proc_info = proc_info,
> .info = host_info,
>
> /* command interface -- queued only */
> .queuecommand = queuecommand,
>
> /* error and abort handlers */
> .eh_abort_handler = command_abort,
> .eh_device_reset_handler = device_reset,
> .eh_bus_reset_handler = bus_reset,
>
> /* queue commands only, only one command per LUN */
> .can_queue = 1,
> .cmd_per_lun = 1,
>
> /* unknown initiator id */
> .this_id = -1,
>
> .slave_alloc = slave_alloc,
> .slave_configure = slave_configure,
>
> /* lots of sg segments can be handled */
> .sg_tablesize = SCSI_MAX_SG_CHAIN_SEGMENTS,
>
> /* limit the total size of a transfer to 120 KB */
> .max_sectors = 240,
>
> If you go to 8 sectors here, you should get the absolute worst case.
If you check trace of usbmon, 'dd if=/dev/sda iflag=direct bs=4k count=xxx'
generates the 4k data stage per transfer(cbw/data/csw).
So there is no difference between them.
Thanks,
--
Ming Lei
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