Am Montag, 2. Juli 2007 schrieb Alan Stern:
> On Mon, 2 Jul 2007, Oliver Neukum wrote:
>
> > > I don't think so. For one thing, we'd be allocating fewer URBs. For
> > > another, the total number of submissions would be the same; they would
> > > just be spread out in time instead of all at once.
> >
> > But the number of interrupts would grow. The ideal number of interrupts
> > per transfer is 1. If you can avoid using more by using a bit more
> > memory, is a wiÅning strategy.
>
> Currently the number of interrupts per transfer is larger than 1. Of
> course we can change that, but should we? On small systems, saving a
> little CPU time by using a lot more memory is not a win.
It is the current design goal. The sg code requests an interrupt only for
the last element of the scatter list.
> > > Actually, the best way to approach this would be to relax the guarantee
> > > that completion routines are called with interrupts disabled. There's
> > > no real reason for that guarantee; it's just an historical remnant.
> >
> > It speeds up execution in real interrupts, which is good.
>
> I don't buy that. Leaving interrupts disabled 90% of the time would
> also speed up execution. But it would ruin latency.
>
> > Completion handlers might be called in a bottom half, but this
> > is a rather intrusive change.
>
> We don't need bottom halves. Just remove the guarantee that interrupts
> will be disabled.
OK, very well. How shall we split the audit load? I volunteer for
drivers/usb/serial
Regards
Oliver
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