On Fri, 13 Jun 2008 20:39:48 EDT erik quanstrom <[EMAIL PROTECTED]> wrote: > > 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.
Already tried. echo 'dma on' > /dev/sdC0/ctl doesn't make any difference in performance. > > 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? Just that if you have no incentive to virtualize IO, you are unlikely to think about making it efficient. > i find there's a certain simplicty in dealing directly > with hardware, provided one has documentation. Provided it is complete and the h/w well designed and interface regular. Unfortunately not all that common. > 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. Ha! First we have to get there.
