> On a T42 running FreeBSD, a stock FreeBSD-4.11/qemu gets > 18MB/s & plan9/qemu gets 3MB/s. Both tested by writing 100MB > from /dev/zero to a file. Neither needs any special drivers. > > I think part of the performance problem is qemu emulates an > early Intel ATA controller chip (PIIX3) and perhaps plan9 > does not do certain optimizations. It would not be too hard > to emulate a more modern controller.
try turning dma on. it is very unlikely that plan 9 is missing some important ata optimization. > IMHO a virtualizable processor is the necessary first step as > it clears one's mind about what not to do in an efficient > virtualizable IO architecture! unless you are contemplating a processor with i/o instructions, what does the processor have to do with i/o architecture? > Emulating grotty device > registers with horrible side-effects is just too painful and > one would be forced to abstract that out. Probably too late > for that! i find there's a certain simplicty in dealing directly with hardware, provided one has documentation. but just wait, there will come a day when people complain about the nasty registers in vm and how it would be good to abstract that stuff out. i think that may have been yesterday. - erik
