Russell King - ARM Linux wrote: > > On Wed, Dec 12, 2001 at 02:28:54PM -0500, [EMAIL PROTECTED] wrote: > > Meanwhile, it would appear that no PCI devices are currently taking > > advantage of this support anyway. I've looked at Netwinder PCI > > config and AFAICT no PCI devices make use of this resource. > > Hang on, I'll turn off all my systems with PCI support. Why do we need > PCI support now? 8) > > > I could use an education here if anyone can offer clues. Why include > > support for a feature which nothing currently uses? : ) > > Seriously, there are devices that have prefetchable memory regions on > them, and if you can make use of them, you get higher performance out > of the PCI bus - for instance, if your framebuffer is in a PCI prefetchable > region (which one of the machines I have here is), then consecutive CPU > reads in that region will use less bus cycles since the information gets > cached on the host bridge.
Ok, so if my PCI graphics card supports prefetch memory region then it will be config'd to take advantage of this. Do you know if Matrox Millenium II supports prefetch? I have one available for test on Integrator. But I haven't looked at this one yet. Meanwhile, the DEC21285 bridge in Netwinder seems to be configured to support prefetch. Yet none of the PCI functions on this target appear to take advantage of prefetch (probably 'cause none support it? : ). That was the point I made above. So why have prefetch support at all on a target which doesn't include any PCI functions which are prefetch capable? Never, mind. Obviously because it uses a common dec21285 driver used on other targets which can take advantage of this suport. > > Also, several mainline Linux folk have expressed an interest in this work > as a means of getting better performance from their systems. Yeah, it certainly can help performance. But it can often expose subtle system bugs too. _______________________________________________ http://lists.arm.linux.org.uk/mailman/listinfo/linux-arm Please visit the above address for information on this list.
