Re: [kvm-devel] kvm-27 vs 28 I/O speed

[Luca <kro...@gm...>]

On 7/16/07, Avi Kivity <av...@qu...> wrote:
> Luca wrote:
> > On 7/15/07, Luca <kro...@gm...> wrote:
> >> On 7/15/07, Luca <kro...@gm...> wrote:
> >> > On 7/13/07, Dave Hansen <hav...@us...> wrote:
> >> > > diff -ru kvm-fast-dmesg.txt kvm-slow-dmesg.txt
> >> > >
> >> > >  Linux version 2.6.22 (dave@kernel) (gcc version 4.1.2 (Ubuntu
> >> 4.1.2-0ubuntu4)) #13 Wed Jul 11 15:27:01 PDT 2007
> >> >
> >> > Is this a vanilla 2.6.22? 32 bit?
> >> >
> >> > > @@ -107,20 +90,21 @@
> >> > >  PIIX3: IDE controller at PCI slot 0000:00:01.1
> >> > >  PIIX3: chipset revision 0
> >> > >  PIIX3: not 100% native mode: will probe irqs later
> >> > > -PIIX3: neither IDE port enabled (BIOS)
> >> > > +    ide0: BM-DMA at 0x1400-0x1407, BIOS settings: hda:pio, hdb:pio
> >> > > +    ide1: BM-DMA at 0x1408-0x140f, BIOS settings: hdc:pio, hdd:pio
> >> >
> >> > Hum, FC6 PIIX driver always comes up with the same mode, regardless of
> >> > what I'm doing to the controller...
> >>
> >> Ok, now I'm confused...
> >>
> >> pci_config_write: PIIX3 IDE: addr=40 val=00008000 len=2
> >> pci_config_write: PIIX3 IDE: addr=42 val=00008000 len=2
> >>
> >> I'm using KVM-27 userspace, and the BIOS is enabling both ports. So...
> >> linux shouldn't think that the ports are disabled (yet I saw the same
> >> thing with FC7 and libata).
> >
> > Oh fuck, it's obvious... If you don't supply -L on the command line
> > KVM ends up using the BIOS in the default system directory
> > (/usr/share{,local}/qemu); on my system this the BIOS installed by
> > QEMU 0.9, which does *not* enable the IDE ports. OTOH the BIOS file
> > shipped with KVM does enable the ports.
> > I guess that you're seeing the same thing: you used to run KVM+QEMU
> > bios (ports disabled - fast); then KVM started to enable IDE ports
> > (even with QEMU bios) and you saw a regression.
> > Can you re-test KVM 27 with it's BIOS (i.e. use something like -L
> > ~/src/kvm-27/qemu/pc-bios)?
> >
> > FYI I'm seeing a better tput with MWDMA2 (ports enabled) rather than
> > with PIO (ports disabled).
>
> So, would it be correct to revert the patch enabling the ports, assuming
> people use the kvm-supplied bios?

I think so. Where does the BIOS come from? Latest Bochs?

Luca