Re: [PATCH] acenic - don't spin in hard_start_xmit when ring fills

[Stephen Hemminger <shemminger@xxxxxxxx>]

On Thu, 16 Sep 2004 16:50:42 -0700
"David S. Miller" <davem@xxxxxxxxxxxxx> wrote:

> On Thu, 16 Sep 2004 16:42:06 -0700
> Stephen Hemminger <shemminger@xxxxxxxx> wrote:
> 
> > NO, the bus just isn't fast enough to keep up with the number of small
> > packets I am shoving at it.
> > 
> > You got TX_LOCKED and TX_BUSY confused. The problem is drivers that
> > don't check to see if the last packet sent fills the ring and stop
> > themselves.
> 
> I understand.
> 
> But that still makes this change buggy.  I believe the two choices
> are:
> 
> 1) Accept this spinning performance characteristic of the
>    acenic driver.

What if there is buggy, hardware that never drains the ring.
It can happen.

> 2) Finally give up on acenic's clever lockless scheme and add
>    the necessary locking + start/stop tx flow control so it
>    will never have to return TX_BUSY except in absolutely
>    catastrophic failure cases.

I'll code up a non-lockless version and see if makes any real difference.