[U-Boot] usb_test_unit_ready called every block read - performance

Marek Vasut
2012-08-18T23:16:25Z

Dear Jim Shimer,

> Hi Marek,
>
> I looked at the ext4 branch. It looks like he has the patch to remove the
> usb_test_unit_ready() calls which were not needed. Actually those calls are
> commented out on that branch:
> #if 0
> if (usb_test_unit_ready(srb, ss)) {
> printf("Device NOT ready\n Request Sense returned %02X
> %02X"
> " %02X\n", srb->sense_buf[2], srb->sense_buf[12],
> srb->sense_buf[13]);
> return 0;
> }
> #endif
>
> In the u-boot-usb.git, this code is removed so at some point there will be
> a merge conflict.
>
> Also the ext4 branch still has the mdelay(5) always being done in
> usb_stor_BBB_transport() line 696 which we found to be the largest
> performance killer.

The ext4 branch doesn't contain a few other things indeed. Can you try applying
the ext4 patches on uboot-usb and retest?

> Regards,
> Jim
>
> On Sun, Aug 12, 2012 at 7:54 PM, Marek Vasut <marex@denx.de> wrote:
> > Dear Jim Shimer,
> >
> > > While tuning ext2load, we found that usb_test_unit_ready was being
> > > called every block read. We compared the usb block storage to the
> > > scsi block storage cmd_scsi.c, and found that the scsi device was only
> > > calling its scsi_setup_test_unit_ready() during scsi_can. It appears
> > > that usb_test_unit_ready() really only needs to be called once during
> > > usb_stor_scan(), via usb_stor_get_info(). Is there a particular
> > > reason usb_test_unit_ready is called for every block read, or do you
> > > think its
> >
> > ok
> >
> > > to only call during usb_stor_scan()? We're finding this speeds up
> >
> > ext2load
> >
> > > quite a bit.
> >
> > Jim, did we get anywhere on this one ? Can you try with the new ext4 code
> > in
> > Wolfgangs' u-boot-master/ext4 branch?
> >
> > > Regards,
> > > Jim
> >
> > Best regards,
> > Marek Vasut

Best regards,
Marek Vasut