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.
Regards
Oliver
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