On Wed, Jan 31, 2001 at 12:47:10AM +1100, Andrew Morton wrote:
> Andi Kleen wrote:
> > On Tue, Jan 30, 2001 at 10:08:02AM +0100, Andrew Morton wrote:
> > > Lots of interesting things here.
> > >
> > > - eepro100 generates more interrupts doing TCP Tx, but not
> > > TCP Rx. I assume it doesn't do Tx mitigation?
> > The Intel driver (e100.c) uploads special firmware and does it for RX and
> > TX.
> > eepro100 doesn't. Perhaps you could measure that driver too?
That's about RX mitigation, where a special hardware assistance is required.
For TX interrupts, the current driver arbitrarily asks for a TX interrupt
every forth packet (to do garbage collection).
> Sure. Anyone have a URL for intel's driver?
> > >
> > > - Changing eepro100 to use IO operations instead of MMIO slows
> > > down this dual 500MHz machine by less than one percent at
> > > 100 mbps. At 12,000 interrupts per second. Why all the fuss
> > > about MMIO?
> > iirc Ingo at some point found at some monster machine that the IO operations
> > in the eepro100 interrupt handler dominated some Tux profile.
The same was reported by kumon@xxxxxxxxxxxxxxxxxx
I think that serialization effects of IO instructions lead to them staying at
the top of profile.