On Tue, Jun 04, 2002 at 09:47:22AM -0700, Lars Eggert wrote:
> Luigi Rizzo wrote:
> >>> BTW if you use polling, you have to be careful in the place
> >>> where you put the call to if_tx_rdy() to make sure that it
> >>> catches the tx queue becoming empty only once and not at every
> >>> polling cycle.
> >>
> >> How about at the very end of sis_intr(), as a new "else" branch of
> >> the queue length check, like this:
> >
> > except that sis_intr is never called when you use polling :(
>
> Doh. You're right, of course.
>
> A new "else" branch of the corresponding "if" in sis_poll() would fire
> on each poll while the queue is empty, so I guess I'll put the call at
> the end of the "while" loop in sis_txeof(), after the mbuf is freed.
and _if_ the mbuf is freed.
In any case it is more a matter of efficiency than of correctness.
Even if you call repeatedly if_tx_rdy() when the device queue is empty
(and the pipe is idle, otherwise at the first occurrence it will
transmit a packet making the transmit queue not empty anymore)
the pipe will not 'accumulate' credits.
cheers
luigi
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