Re: 2.6.8-rc3-mm2

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Tue, Aug 10, 2004 at 03:01:22PM +0200, Ingo Molnar wrote:
> 
> * William Lee Irwin III <wli@holomorphy.com> wrote:
> 
> > On Tue, Aug 10, 2004 at 02:55:29PM +0200, Ingo Molnar wrote:
> > > i'd guess it's the con->write() in __call_console_drivers() that makes
> > > the difference. (i.e. touching the framebuffer)
> > 
> > This is serial port IO; would that make the same kind of difference?
> 
> serial port IO is even more heavy, it also generates IRQ traffic.

Except serial console IO does not generate _any_ IRQ traffic - it
purposely disables IRQs on the device before starting any IO to
prevent any user-level IO interfering with the console output.

It does, however, create a fair amount of IO reads and writes to
the serial port.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core