> I am thinking about the TLB. In principle we want all
> urbs a driver uses to be on the same page.

At USB 1.1 speeds, with URB submit/complete
cycles typically at least one millisecond, I can't
see that as a very big issue.

For high speed transfers, it'll be more interesting,
but I'm fairly sure other performance issues will
hit before that one does.  Like not using bulk
queuing in drivers ... :)


> > > Do we save memory ?
> >
> > If not, that's a global kernel issue and not just
> > a USB one.
> >
> > >    Is the slab cache
> > > limited to power of 2 objects ?
> >
> > You can create caches of whatever size you want.
> > Sharing the general purpose caches saves memory.
> 
> Even if we save space by having a lesser overhead
> by not using power of 2 objects ?

As a rule, for objects that small, yes.  How many URBs
are going to be allocated at a time, on typical systems,
anyway?  A handful.

- Dave



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