Re: 2.4 vs 2.6 USB mass storage device performance

[David Brownell <david-b@xxxxxxxxxxx>]

On Friday 30 November 2007, Alan Stern wrote:
> > how does it
> > effect the performance?
> 
> It doesn't affect performance at all.
> 
> > I did change this API too to
> > use usb_sg routines but couldn't test it as it never
> > gets called while I do scsi xfer.
> 
> That's why it doesn't affect the performance!  :-)

And you won't be able to convert to the usb_sg_*() routines
without updating all the HCDs and usbcore to handle the
related clean semantics for URB completion and queueing.

The scope of those changes is the reason I described the
performance limitation as intrinsic to the 2.4 USB stack,
and not amenable to fixing.

- Dave


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